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                                                                   Exhibit 10.19

                           THIRD AMENDED AND RESTATED
                          REGISTRATION RIGHTS AGREEMENT

      THIS THIRD AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT (the
"Agreement"), made as of December 22, 2003, by and among Egenera, Inc., a
Delaware corporation (the "Company"), and the persons listed as Purchasers in
the attached Schedule I (collectively, the "Purchasers" and individually, a
"Purchaser").

      WHEREAS, certain of the Purchasers (the "Existing Purchasers") hold an
aggregate of 22,739,475 shares (the "Series A Preferred Shares") of the
Company's Series A Convertible Preferred Stock, $.001 par value (the "Series A
Preferred Stock"), an aggregate of 30,485,521 shares (the "Series B Preferred
Shares") of the Company's Series B Convertible Preferred Stock, $.001 par value
(the "Series B Preferred Stock"), and an aggregate of 33,714,517 shares (the
"Series C Preferred Shares") of Series C Convertible Preferred Stock, $.001 par
value (the "Series C Preferred Stock"), and hold certain registration rights in
connection therewith pursuant to a Second Amended and Restated Registration
Rights Agreement dated as of May 16, 2002, by and among the Existing Purchasers
and the Company (as previously amended, the "Prior Agreement");

      WHEREAS, certain of the Purchasers (the "Series D Purchasers") are
entering into a Series D Convertible Preferred Stock Purchase Agreement (the
"Series D Agreement") of even date herewith by and among the Series D Purchasers
and the Company providing for the purchase of an aggregate of up to 11,100,011
shares (the "Series D Preferred Shares") of the Company's Series D Convertible
Preferred Stock, $.001 par value; and

      WHEREAS, it is a condition to the obligations of the Series D Purchasers
under the Series D Agreement that this Agreement be executed by the parties
hereto, and the parties are willing to execute this Agreement and to be bound by
the provisions hereof.

      NOW, THEREFORE, in consideration of the mutual covenants and agreements
contained herein and in the Series D Agreement and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
parties to the Prior Agreement hereby agree that the Prior Agreement shall be
amended and restated in its entirety by this Agreement, and the parties hereto
further agree as follows:

      1.    Certain Definitions. As used in this Agreement, the following terms
shall have the following respective meanings:

            "Commission" shall mean the Securities and Exchange Commission, or
any other federal agency at the time administering the Securities Act.

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            "Common Stock" shall mean the Common Stock, $.001 par value, of the
Company, as constituted as of the date of this Agreement.

            "Conversion Shares" shall mean shares of Common Stock issued or
issuable upon conversion of the Preferred Shares.

            "Crosslink", "TCV" and "Investor Affiliates" shall have the meanings
given them in the Amended and Restated IPO Allocation Agreement described below
in the definition of "Restricted Stock".

            "Exchange Act" shall mean the Securities Exchange Act of 1934, as
amended, or any similar federal statute, and the rules and regulations of the
Commission thereunder, all as the same shall be in effect at the time.

            "Preferred Shares" shall collectively mean the Series A Preferred
Shares, the Series B Preferred Shares, the Series C Preferred Shares and Series
D Preferred Shares.

            "Registration Expenses" shall mean the expenses so described in
Section 8.

            "Restricted Stock" shall mean (i) the Conversion Shares, (ii) any
shares of Common Stock (or shares of Common Stock issued upon conversion of any
securities of the Company) purchased by Crosslink, TCV, or any Investor
Affiliates in a private placement as contemplated by Section 2 of that certain
Amended and Restated IPO Allocation Agreement dated as of the date hereof (the
"IPO Allocation Agreement") between the Company, Crosslink Capital, Inc. and TCV
("Allocation Agreement Shares"), (iii) solely in connection with a Follow-on
Offering (as defined in Section 1(j) of the IPO Allocation Agreement), shares of
Common Stock purchased by Crosslink, TCV, or any Investor Affiliates pursuant to
Section 1 of the IPO Allocation Agreement, and (iv) any shares of the Company's
Common Stock acquired by Crosslink, TCV, and/or any Investor Affiliates from any
currently existing holder of the Company's Common Stock on or prior to February
27, 2004, but excluding for purposes of clauses (i), (ii), (iii), (iv) above,
any shares of capital stock of the Company which have been (a) registered under
the Securities Act pursuant to an effective registration statement filed
thereunder and disposed of in accordance with the registration statement
covering them or (b) publicly sold pursuant to Rule 144 under the Securities
Act.

            "Securities Act" shall mean the Securities Act of 1933, as amended,
or any similar federal statute, and the rules and regulations of the Commission
thereunder, all as the same shall be in effect at the time.

            "Selling Expenses" shall mean the expenses so described in Section
8.

      2.    Restrictive Legend. Each certificate representing Preferred Shares
or Conversion Shares shall, except as otherwise provided in this Section 2 or in
Section 3, be stamped or otherwise imprinted with a legend substantially in the
following form:

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            "The securities represented by this certificate have not been
            registered under the Securities Act of 1933 or applicable state
            securities laws. These securities have been acquired for investment
            and not with a view to distribution or resale, and may not be sold,
            mortgaged, pledged, hypothecated or otherwise transferred without an
            effective registration statement for such securities under the
            Securities Act of 1933 and applicable state securities laws, or the
            availability of an exemption from the registration provisions of the
            Securities Act of 1933 and applicable state securities laws."

A certificate shall not bear such legend if in the opinion of counsel reasonably
satisfactory to the Company (it being agreed that Testa, Hurwitz & Thibeault,
LLP, Heller Ehrman White & McAuliffe LLP or Gunderson Dettmer Stough Villeneuve
Franklin & Hachigian, LLP shall be satisfactory) the securities represented
thereby may be publicly sold without registration under the Securities Act and
any applicable state securities laws.

      3.    Notice of Proposed Transfer. Prior to any proposed transfer of any
Preferred Shares or Conversion Shares (other than under the circumstances
described in Sections 4, 5 or 6), the holder thereof shall give written notice
to the Company of its intention to effect such transfer. Each such notice shall
describe the manner of the proposed transfer and, if requested by the Company,
shall be accompanied by an opinion of counsel reasonably satisfactory to the
Company (it being agreed that Testa, Hurwitz & Thibeault, LLP, Heller Ehrman
White & McAuliffe LLP, Gunderson Dettmer Stough Villeneuve Franklin & Hachigian,
LLP or Barry Bendes, Esq. shall be satisfactory) to the effect that the proposed
transfer may be effected without registration under the Securities Act and any
applicable state securities laws, whereupon the holder of such stock shall be
entitled to transfer such stock in accordance with the terms of its notice;
provided, however, that no such opinion of counsel shall be required for a
transfer to one or more partners, members or affiliates of the transferor (in
the case of a transferor that is a partnership or a limited liability company,
respectively) or to an affiliated corporation (in the case of a transferor that
is a corporation) or to a venture capital fund under common investment
management; provided, further, however, that any transferee other than a
partner, member or affiliate of, or a venture capital fund under common
investment management with, the transferor shall execute and deliver to the
Company a representation letter in form reasonably satisfactory to the Company's
counsel to the effect that the transferee is acquiring restricted stock for its
own account for investment purposes and without any view to distribution
thereof. Each certificate for Preferred Shares or Conversion Shares transferred
as above provided shall bear the legend set forth in Section 2, except that such
certificate shall not bear such legend if (i) such transfer is in accordance
with the provisions of Rule 144 (or any other rule permitting public sale
without registration under the Securities Act) or (ii) the opinion of counsel
referred to above is to the further effect that the transferee and any
subsequent transferee (other than an affiliate of the Company) would be entitled
to transfer such securities in a public sale without registration under the
Securities Act. The restrictions provided for in this Section 3 shall not apply
to securities which are not required to bear the legend prescribed by Section 2
in accordance with the provisions of that Section.

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      4.    Required Registration. (a) At any time after the earliest of (i) six
months after any registration statement covering a public offering of securities
of the Company under the Securities Act shall have become effective, (ii) six
months after the Company shall have become a reporting company under Section 12
of the Exchange Act, and (iii) June 30, 2006, the holders of Restricted Stock
constituting at least 20% of the total shares of Restricted Stock then
outstanding may request the Company to register under the Securities Act all or
any portion of the shares of Restricted Stock held by such requesting holder or
holders for sale in the manner specified in such notice, provided that the
shares of Restricted Stock for which registration has been requested shall
constitute at least 10% of the total shares of Restricted Stock originally
issued if such holder or holders shall request the registration of less than all
shares of Restricted Stock then held by such holder or holders (or any lesser
percentage if the reasonably anticipated aggregate price to the public of such
public offering would exceed $5,000,000). For purposes of this Section 4 and
Sections 5, 6, 14(a) and 14(d), the term "Restricted Stock" shall be deemed to
include the number of shares of Restricted Stock which would be issuable to a
holder of Preferred Shares upon conversion of all Preferred Shares held by such
holder at such time, provided, however, that the only securities which the
Company shall be required to register pursuant hereto shall be shares of Common
Stock, and provided, further, however, that, in any underwritten public offering
contemplated by this Section 4 or Sections 5 and 6, the holders of Preferred
Shares shall be entitled to sell such Preferred Shares to the underwriters for
conversion and sale of the shares of Common Stock issued upon conversion
thereof. Notwithstanding anything to the contrary contained herein, no request
may be made under this Section 4 within 180 days after the effective date of a
registration statement filed by the Company covering a firm commitment
underwritten public offering in which the holders of Restricted Stock shall have
been entitled to join pursuant to Sections 5 or 6 and in which there shall have
been effectively registered all shares of Restricted Stock as to which
registration shall have been requested.

            (b) Following receipt of any notice under this Section 4, the
Company shall immediately notify all holders of Restricted Stock from whom
notice has not been received and shall use commercially reasonable efforts to
register under the Securities Act, for public sale in accordance with the method
of disposition specified in such notice from requesting holders, the number of
shares of Restricted Stock specified in such notice (and in all notices received
by the Company from other holders within 30 days after the giving of such notice
by the Company). If such method of disposition shall be an underwritten public
offering, the Company shall designate the managing underwriter of such offering,
subject to the approval of the holders of a majority of the shares of Restricted
Stock to be sold in such offering, which approval shall not be unreasonably
withheld or delayed. The Company shall be obligated to register Restricted Stock
pursuant to this Section 4 on four occasions only, provided, however, that such
obligation shall be deemed satisfied only when a registration statement covering
all shares of Restricted Stock specified in notices received as aforesaid, for
sale in accordance with the method of disposition specified by the requesting
holders, shall have become effective and, if such method of disposition is a
firm commitment underwritten public offering, all such shares shall have been
sold pursuant thereto.

            (c) The Company shall be entitled to include in any registration
statement referred to in this Section 4, for sale in accordance with the method
of disposition specified by

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the requesting holders, shares of Common Stock to be sold by the Company for its
own account, except as and to the extent that, in the opinion of the managing
underwriter (if such method of disposition shall be an underwritten public
offering), such inclusion would adversely affect the marketing of the Restricted
Stock to be sold. Except for registration statements on Form S-4, S-8 or any
successor thereto, the Company will not file with the Commission any other
registration statement with respect to its Common Stock, whether for its own
account or that of other stockholders, from the date of receipt of a notice from
requesting holders pursuant to this Section 4 until the completion of the period
of distribution of the registration contemplated thereby.

      5.    Incidental Registration. If the Company at any time (other than
pursuant to Section 4 or Section 6) proposes to register any of its securities
under the Securities Act for sale to the public, whether for its own account or
for the account of other security holders or both (except with respect to
registration statements on Forms S-4, S-8 or another form not available for
registering the Restricted Stock for sale to the public), each such time it will
give written notice to all holders of outstanding Restricted Stock of its
intention so to do. Upon the written request of any such holder, received by the
Company within 30 days after the giving of any such notice by the Company, to
register any of its Restricted Stock, the Company will use commercially
reasonable efforts to cause the Restricted Stock as to which registration shall
have been so requested to be included in the securities to be covered by the
registration statement proposed to be filed by the Company, all to the extent
requisite to permit the sale or other disposition by the holder of such
Restricted Stock so registered. In the event that any registration pursuant to
this Section 5 shall be, in whole or in part, an underwritten public offering of
Common Stock, the number of shares of Restricted Stock to be included in such an
underwriting may be reduced (pro rata among the requesting holders based upon
the number of shares of Restricted Stock owned by such holders) if and to the
extent that the managing underwriter shall be of the opinion that such inclusion
would adversely affect the marketing of the securities to be sold by the Company
therein, provided, however, that such number of shares of Restricted Stock shall
not be reduced if any shares are to be included in such underwriting for the
account of any person other than the Company or requesting holders of Restricted
Stock, and provided, further, however, that in no event (except for in
connection with the initial public offering of Common Stock) may less than
one-fourth of the total number of shares of Common Stock to be included in such
underwriting be made available for shares of Restricted Stock. Notwithstanding
the foregoing provisions, the Company may withdraw any registration statement
referred to in this Section 5 without thereby incurring any liability to the
holders of Restricted Stock.

      6.    Registration on Form S-3. (a) If at any time (i) a holder or holders
of Preferred Shares or Restricted Stock request that the Company file a
registration statement on Form S-3 or any successor thereto for a public
offering of all or any portion of the shares of Restricted Stock held by such
requesting holder or holders, the reasonably anticipated aggregate price to the
public of which would exceed $1,000,000, and (ii) the Company is a registrant
entitled to use Form S-3 or any successor thereto to register such shares, then
the Company shall use its commercially reasonable efforts to register under the
Securities Act on Form S-3 or any successor thereto, for public sale in
accordance with the method of disposition specified in such notice, the number
of shares of Restricted Stock specified in such notice. Whenever the Company is
required by this

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Section 6 to use commercially reasonable efforts to effect the registration of
Restricted Stock, each of the procedures and requirements of Section 4
(including but not limited to the requirement that the Company notify all
holders of Restricted Stock from whom notice has not been received and provide
them with the opportunity to participate in the offering) shall apply to such
registration, provided, however, that the maximum number of registrations on
Form S-3 which may be requested and obtained under this Section 6 shall be two
(2) per any twelve (12) month period during the five year period after the
Company qualifies as a registrant entitled to use Form S-3 to register such
shares and an aggregate maximum of ten (10) such registrations, provided,
further, however, that the requirements contained in the first sentence of
Section 4(a) shall not apply to any registration on Form S-3 which may be
requested and obtained under this Section 6 and provided, further, however, the
registration rights of a holder or holders of Preferred Shares or Restricted
Stock under this Section 6 shall not apply if all of such Preferred Shares or
Restricted Stock held by such holder or holders may be sold under Rule 144
during any ninety (90) day period, it being understood that the registration
rights of such holder or holders under this Section 6 shall, subject to any
other limitations described in this Section 6, apply once again at such time as
all of such Preferred Shares or Restricted Stock held by such holder or holders
may no longer be sold under Rule 144 during any ninety (90) day period.

            (b) At any time after the Company is a registrant entitled to use
Form S-3 or any successor thereto to register such shares then, in the event
that Form S-3 or any successor thereto is unavailable for any registration of
the Restricted Stock hereunder, the Company (i) shall register the sale of the
Restricted Stock on another appropriate form and (ii) undertake to register the
Restricted Stock on Form S-3 or any successor thereto as soon as such form is
available, provided that the Company shall maintain the effectiveness of the
Registration Statement then in effect until such time as a Registration
Statement on Form S-3 covering the Restricted Stock has been declared effective
by the Commission.

      7.    Registration Procedures. If and whenever the Company is required by
the provisions of Sections 4, 5 or 6 to use commercially reasonable efforts to
effect the registration of any shares of Restricted Stock under the Securities
Act, the Company will, as expeditiously as possible:

            (a) prepare and file with the Commission a registration statement
(which, in the case of an underwritten public offering pursuant to Section 4,
shall be on Form S-1 or other form of general applicability satisfactory to the
managing underwriter selected as therein provided) with respect to such
securities and use commercially reasonable efforts to cause such registration
statement to become and remain effective for the period of the distribution
contemplated thereby (determined as hereinafter provided);

            (b) prepare and file with the Commission such amendments and
supplements to such registration statement and the prospectus used in connection
therewith as may be necessary to keep such registration statement effective for
the period specified in paragraph (a) above and comply with the provisions of
the Securities Act with respect to the disposition of all Restricted Stock
covered by such registration statement in accordance with the sellers' intended
method of disposition set forth in such registration statement for such period;

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            (c) furnish to each seller of Restricted Stock and to each
underwriter such number of copies of the registration statement and the
prospectus included therein (including each preliminary prospectus and amendment
thereto) as such persons reasonably may request in order to facilitate the
public sale or other disposition of the Restricted Stock covered by such
registration statement;

            (d) use commercially reasonable efforts to register or qualify the
Restricted Stock covered by such registration statement under the securities or
"blue sky" laws of such jurisdictions as the sellers of Restricted Stock or, in
the case of an underwritten public offering, the managing underwriter reasonably
shall request, provided, however, that the Company shall not for any such
purpose be required to qualify generally to transact business as a foreign
corporation in any jurisdiction where it is not so qualified or to consent to
general service of process in any such jurisdiction;

            (e) use commercially reasonable efforts to list the Restricted Stock
covered by such registration statement with any securities exchange on which the
Common Stock of the Company is then listed;

            (f) immediately notify each seller of Restricted Stock and each
underwriter under such registration statement, at any time when a prospectus
relating thereto is required to be delivered under the Securities Act, of the
happening of any event of which the Company has knowledge as a result of which
the prospectus contained in such registration statement, as then in effect,
includes an untrue statement of a material fact or omits to state a material
fact required to be stated therein or necessary to make the statements therein
not misleading in light of the circumstances then existing, and each Purchaser
hereby covenants and agrees, upon receipt of such notification, to discontinue
disposition of Restricted Shares pursuant to such registration statement until
the time of effectiveness of an amendment thereto or a supplement to such
prospectus included therein as may be necessary so that, as thereafter delivered
to the purchasers of such Restricted Shares, such prospectus shall not include
an untrue statement of a material fact or omit to state a material fact required
to be stated therein or necessary to make the statements therein not misleading
in light of the circumstances then existing;

            (g) if the offering is underwritten and at the request of any seller
of Restricted Stock, use commercially reasonable efforts to furnish on the date
that Restricted Stock is delivered to the underwriters for sale pursuant to such
registration: (i) an opinion dated such date of counsel representing the Company
for the purposes of such registration, addressed to the underwriters and to such
seller, stating that such registration statement has become effective under the
Securities Act and that (A) to the best knowledge of such counsel, no stop order
suspending the effectiveness thereof has been issued and no proceedings for that
purpose have been instituted or are pending or contemplated under the Securities
Act, (B) the registration statement, the related prospectus and each amendment
or supplement thereof comply as to form in all material respects with the
requirements of the Securities Act (except that such counsel need not express
any opinion as to financial statements contained therein) and (C) to such other
effects as reasonably may be requested by counsel for the underwriters or by
such seller or its counsel

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and (ii) a letter dated such date from the independent public accountants
retained by the Company, addressed to the underwriters and to such seller,
stating that they are independent public accountants within the meaning of the
Securities Act and that, in the opinion of such accountants, the financial
statements of the Company included in the registration statement or the
prospectus, or any amendment or supplement thereof, comply as to form in all
material respects with the applicable accounting requirements of the Securities
Act, and such letter shall additionally cover such other financial matters
(including information as to the period ending no more than five business days
prior to the date of such letter) with respect to such registration as such
underwriters reasonably may request; and

            (h) make available for inspection by each seller of Restricted
Stock, any underwriter participating in any distribution pursuant to such
registration statement, and any attorney, accountant or other agent retained by
such seller or underwriter, all financial and other records, pertinent corporate
documents and properties of the Company, and cause the Company's officers,
directors and employees to supply all information reasonably requested by any
such seller, underwriter, attorney, accountant or agent in connection with such
registration statement.

      For purposes of Section 7(a) and 7(b) and of Section 4(c), the period of
distribution of Restricted Stock in a firm commitment underwritten public
offering shall be deemed to extend until each underwriter has completed the
distribution of all securities purchased by it, and the period of distribution
of Restricted Stock in any other registration shall be deemed to extend until
the earlier of the sale of all Restricted Stock covered thereby and 120 days
after the effective date thereof.

      In connection with each registration hereunder, the sellers of Restricted
Stock will furnish to the Company in writing such information with respect to
themselves and the proposed distribution by them as reasonably shall be
necessary in order to assure compliance with federal and applicable state
securities laws and to make the registration statement correct, accurate and
complete in all material respects with respect to such sellers' participating in
the offering; provided, however, that this requirement shall not be deemed to
limit any disclosure obligation arising out of any seller's relationship to the
Company if one of such seller's agents or affiliates is an officer, director or
control person of the Company. In addition, in connection with any underwritten
registration, the sellers shall, if requested by the Company, execute such other
underwriting related agreements, which are reasonably satisfactory to them and
which shall contain such provisions as may be customary and reasonable in order
to accomplish the registration of the Restricted Stock.

      In connection with each registration pursuant to Sections 4, 5 or 6
covering an underwritten public offering, the Company and each seller agree to
enter into a written agreement with the managing underwriter selected in the
manner herein provided in such form and containing such provisions as are
customary in the securities business for such an arrangement between such
underwriter and companies of the Company's size and investment stature.

      8.    Expenses. All expenses incurred by the Company in complying with
Sections 4, 5 and 6, including, without limitation, all registration and filing
fees, printing expenses, fees and

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disbursements of counsel and independent public accountants for the Company,
fees and expenses (including counsel fees for one counsel of the holders of
Restricted Stock) incurred in connection with complying with state securities or
"blue sky" laws, fees of the National Association of Securities Dealers, Inc.,
transfer taxes, fees of transfer agents and registrars, costs of insurance and
fees and disbursements of one counsel for the sellers of Restricted Stock, but
excluding any Selling Expenses, are called "Registration Expenses". All
underwriting discounts and selling commissions applicable to the sale of
Restricted Stock are called "Selling Expenses".

      The Company will pay all Registration Expenses in connection with each
registration statement under Sections 4, 5 or 6. All Selling Expenses in
connection with each registration statement under Sections 4, 5 or 6 shall be
borne by the participating sellers in proportion to the number of shares sold by
each, or by such participating sellers other than the Company (except to the
extent the Company shall be a seller) as they may agree.

      9.    Indemnification and Contribution. (a) In the event of a registration
of any of the Restricted Stock under the Securities Act pursuant to Sections 4,
5 or 6, the Company will indemnify and hold harmless each seller of such
Restricted Stock thereunder, each underwriter of such Restricted Stock
thereunder and each other person, if any, who controls such seller or
underwriter within the meaning of the Securities Act, against any losses,
claims, damages or liabilities, joint or several, to which such seller,
underwriter or controlling person may become subject under the Securities Act or
otherwise, insofar as such losses, claims, damages or liabilities (or actions in
respect thereof) arise out of or are based upon any untrue statement or alleged
untrue statement of any material fact contained in any registration statement
under which such Restricted Stock was registered under the Securities Act
pursuant to Sections 4, 5 or 6, any preliminary prospectus or final prospectus
contained therein, or any amendment or supplement thereof, or arise out of or
are based upon the omission or alleged omission to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading, and will reimburse each such seller, each such underwriter and each
such controlling person for any legal or other expenses reasonably incurred by
them in connection with investigating or defending any such loss, claim, damage,
liability or action, provided, however, that the Company will not be liable in
any such case if and to the extent that any such loss, claim, damage or
liability arises out of or is based upon an untrue statement or alleged untrue
statement or omission or alleged omission so made in conformity with information
furnished by any such seller, any such underwriter or any such controlling
person in writing specifically for use in such registration statement or
prospectus.

            (b) In the event of a registration of any of the Restricted Stock
under the Securities Act pursuant to Sections 4, 5 or 6, each seller of such
Restricted Stock thereunder, severally and not jointly, will indemnify and hold
harmless the Company, each person, if any, who controls the Company within the
meaning of the Securities Act, each officer of the Company who signs the
registration statement, each director of the Company, each underwriter and each
person who controls any underwriter within the meaning of the Securities Act,
against all losses, claims, damages or liabilities, joint or several, to which
the Company or such officer, director, underwriter or controlling person may
become subject under the Securities Act or otherwise, insofar as such losses,
claims, damages or liabilities (or actions in respect thereof)

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arise out of or are based upon any untrue statement or alleged untrue statement
of any material fact contained in the registration statement under which such
Restricted Stock was registered under the Securities Act pursuant to Sections 4,
5 or 6, any preliminary prospectus or final prospectus contained therein, or any
amendment or supplement thereof, or arise out of or are based upon the omission
or alleged omission to state therein a material fact required to be stated
therein or necessary to make the statements therein not misleading, and will
reimburse the Company and each such officer, director, underwriter and
controlling person for any legal or other expenses reasonably incurred by them
in connection with investigating or defending any such loss, claim, damage,
liability or action, provided, however, that such seller will be liable
hereunder in any such case if and only to the extent that any such loss, claim,
damage or liability arises out of or is based upon an untrue statement or
alleged untrue statement or omission or alleged omission made in reliance upon
and in conformity with information pertaining to such seller, as such, furnished
in writing to the Company by such seller specifically for use in such
registration statement or prospectus or preliminary amendment or supplement
thereof, and provided, further, however, that the liability of each seller
hereunder shall be limited to the net proceeds received by such seller from the
sale of Restricted Stock covered by such registration statement.

            (c) Promptly after receipt by an indemnified party hereunder of
notice of the commencement of any action, such indemnified party shall, if a
claim in respect thereof is to be made against the indemnifying party hereunder,
notify the indemnifying party in writing thereof, but the omission so to notify
the indemnifying party shall not relieve it from any liability which it may have
to such indemnified party other than under this Section 9 and shall only relieve
it from any liability which it may have to such indemnified party under this
Section 9 if and to the extent the indemnifying party is prejudiced by such
omission. In case any such action shall be brought against any indemnified party
and it shall notify the indemnifying party of the commencement thereof, the
indemnifying party shall be entitled to participate in and, to the extent it
shall wish, to assume and undertake the defense thereof with counsel
satisfactory to such indemnified party, and, after notice from the indemnifying
party to such indemnified party of its election so to assume and undertake the
defense thereof, the indemnifying party shall not be liable to such indemnified
party under this Section 9 for any legal expenses subsequently incurred by such
indemnified party in connection with the defense thereof, provided, however,
that, if the defendants in any such action include both the indemnified party
and the indemnifying party and the indemnified party shall have reasonably
concluded that there may be reasonable defenses available to it which are
different from or additional to those available to the indemnifying party or if
the interests of the indemnified party reasonably may be deemed to conflict with
the interests of the indemnifying party, the indemnified party shall have the
right to select a separate counsel and to assume such legal defenses and
otherwise to participate in the defense of such action, with the expenses and
fees of such separate counsel and other expenses related to such participation
to be reimbursed by the indemnifying party as incurred.

            (d) In order to provide for just and equitable contribution to joint
liability under the Securities Act in any case in which either (i) any holder of
Restricted Stock exercising rights under this Agreement, or any controlling
person of any such holder, makes a claim for indemnification pursuant to this
Section 9 but it is judicially determined (by the entry of a final

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judgment or decree by a court of competent jurisdiction and the expiration of
time to appeal or the denial of the last right of appeal) that such
indemnification may not be enforced in such case notwithstanding the fact that
this Section 9 provides for indemnification in such case, or (ii) contribution
under the Securities Act may be required on the part of any such selling holder
or any such controlling person in circumstances for which indemnification is
provided under this Section 9; then, and in each such case, the Company and such
holder will contribute to the aggregate losses, claims, damages or liabilities
to which they may be subject (after contribution from others) in such proportion
so that such holder is responsible for the portion represented by the percentage
that the public offering price of its Restricted Stock offered by the
registration statement bears to the public offering price of all securities
offered by such registration statement, and the Company is responsible for the
remaining portion; provided, however, that, in any such case, (A) no such holder
will be required to contribute any amount in excess of the net proceeds received
by such holder from the sale of all such Restricted Stock offered by it pursuant
to such registration statement; and (B) no person or entity guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the Securities Act)
will be entitled to contribution from any person or entity who was not guilty of
such fraudulent misrepresentation.

      10.   Changes in Common Stock or Preferred Stock. If, and as often as,
there is any change in the Common Stock or the Preferred Stock by way of a stock
split, stock dividend, combination or reclassification, or through a merger,
consolidation, reorganization or recapitalization, or by any other means,
appropriate adjustment shall be made in the provisions hereof so that the rights
and privileges granted hereby shall continue with respect to the Common Stock or
the Preferred Stock as so changed.

      11.   Rule 144 Reporting. With a view to making available the benefits of
certain rules and regulations of the Commission which may at any time permit the
sale of the Restricted Stock to the public without registration, at all times
after 90 days after any registration statement covering a public offering of
securities of the Company under the Securities Act shall have become effective,
the Company agrees to:

            (a) make and keep public information available, as those terms are
understood and defined in Rule 144 under the Securities Act;

            (b) use commercially reasonable efforts to file with the Commission
in a timely manner all reports and other documents required of the Company under
the Securities Act and the Exchange Act; and

            (c) furnish to each holder of Restricted Stock forthwith upon
request a written statement by the Company as to its compliance with the
reporting requirements of such Rule 144 and of the Securities Act and the
Exchange Act, a copy of the most recent annual or quarterly report of the
Company, and such other reports and documents so filed by the Company as such
holder may reasonably request in availing itself of any rule or regulation of
the Commission allowing such holder to sell any Restricted Stock without
registration.

                                      -11-
<PAGE>

      12.   Representations and Warranties of the Company. The Company
represents and warrants to each Purchaser as follows:

            (a) The execution, delivery and performance of this Agreement by the
Company have been duly authorized by all requisite corporate action and will not
violate any provision of law, any order of any court or other agency of
government, the Charter or By-laws of the Company or any provision of any
indenture, agreement or other instrument to which it or any or its properties or
assets is bound, conflict with, result in a breach of or constitute (with due
notice or lapse of time or both) a default under any such indenture, agreement
or other instrument or result in the creation or imposition of any lien, charge
or encumbrance of any nature whatsoever upon any of the properties or assets of
the Company.

            (b) This Agreement has been duly executed and delivered by the
Company and constitutes the legal, valid and binding obligation of the Company,
enforceable in accordance with its terms.

      13.   Additional Purchasers. Persons or entities that, after the date
hereof, purchase shares of Series D Preferred Stock pursuant to the Series D
Agreement of even date hereof and become "Purchasers" thereunder may (without
the need for approval by any other party to this Agreement) become parties to
this Agreement at the option of the Company by executing and delivering a
counterpart signature page hereto, whereupon they shall be deemed "Purchasers"
for all purposes of this Agreement.

      14.   Miscellaneous.

            (a) All covenants and agreements contained in this Agreement by or
on behalf of any of the parties hereto shall bind and inure to the benefit of
the respective successors and assigns of the parties hereto (including without
limitation transferees of any Preferred Shares or Restricted Stock), whether so
expressed or not, provided, however, that registration rights conferred herein
on the holders of Preferred Shares or Restricted Stock shall only inure to the
benefit of a transferee of Preferred Shares or Restricted Stock if (i) there is
transferred to such transferee at least 10% of the total shares of Restricted
Stock originally issued to the direct or indirect transferor of such transferee
and such transferee is not primarily engaged in any business (other than the
Company) that competes in any material way with the products or services being
developed, manufactured or sold by the Company or (ii) such transferee is a
partner, member, shareholder or affiliate of, or a venture capital fund under
common investment management with, a party hereto and provided, further, that
such transferee becomes a party to this Agreement by executing and delivering to
the Company an Instrument of Accession in the form of Schedule II hereto.

            (b) All notices, requests, consents and other communications
hereunder shall be in writing and shall be delivered in person, mailed by
certified or registered mail, return receipt requested by commercial overnight
courier or sent by fax, addressed as follows:

                                      -12-
<PAGE>

            if to the Company or any other party hereto, at the address of such
party set forth in the Company's records or such address as may have been
furnished to the Company in writing by such party, provided that if such party
is Crosslink Capital, Inc. or Crosslink Ventures IV, L.P., Offshore Crosslink
Omega Ventures IV (a Cayman Islands Unit Trust), Crosslink Omega Ventures IV
GmbH & Co. KG, Omega Bayview IV, L.L.C., Crosslink Crossover Fund III, L.P.,
Crosslink Crossover Fund IV, L.P., or Offshore Crosslink Crossover Fund III,
Unit Trust, a copy shall also be sent to Sarah A. O'Dowd, Esq., Heller Ehrman
White & McAuliffe LLP, 275 Middlefield Road, Menlo Park, California 94025;

            if to any subsequent holder of Preferred Shares or Restricted Stock,
to it at such address as may have been furnished to the Company in writing by
such holder;

or, in any case, at such other address or addresses as shall have been furnished
in writing to the Company (in the case of a holder of Preferred Shares or
Restricted Stock) or to the holders of Preferred Shares or Restricted Stock (in
the case of the Company) in accordance with the provisions of this paragraph.

            (c) This Agreement shall be governed by and construed in accordance
with the laws of the Commonwealth of Massachusetts. Each of the parties hereto
hereby irrevocably and unconditionally consents to submit to the non-exclusive
jurisdiction of the courts of the Commonwealth of Massachusetts and of the
United States of America, located in the Commonwealth of Massachusetts, for any
action, proceeding or investigation in any court or before any governmental
authority ("Litigation") arising out of or relating to this Agreement and the
transactions contemplated hereby, and further agrees that service of any
process, summons, notice or document by U.S. registered mail to its respective
address set forth in this Agreement shall be effective service of process for
any Litigation brought against it in any such court. Each of the parties hereto
hereby irrevocably and unconditionally waives any objection to the laying of
venue of any Litigation arising out of this Agreement or the transactions
contemplated hereby in the courts of the Commonwealth of Massachusetts or the
United States of America, located in the Commonwealth of Massachusetts, and
hereby further irrevocably and unconditionally waives and agrees not to plead or
claim in any such court that any such Litigation brought in any such court has
been brought in an inconvenient forum. Each of the parties irrevocably and
unconditionally waives, to the fullest extent permitted by applicable law, any
and all rights to trial by jury in connection with any Litigation arising out of
or relating to this Agreement or the transactions contemplated hereby.

            (d) This Agreement may not be amended or modified, and no provision
hereof may be waived, without the written consent of the Company and the holders
holding at least two-thirds of the then-outstanding shares of Restricted Stock.

            (e) This Agreement may be executed in two or more counterparts, each
of which shall be deemed an original, but all of which together shall constitute
one and the same instrument.

                                      -13-
<PAGE>

            (f) The obligations of the Company to register shares of Restricted
Stock under Sections 4, 5 or 6 shall: (i) with respect to any holder of
Restricted Stock, not apply at any time that all Restricted Stock held by such
holder may be sold under Rule 144 during any ninety (90) day period, provided
that such obligations will once again apply at such time as all of such
Preferred Shares or Restricted Stock may no longer be sold under Rule 144 during
any ninety (90) day period, and (ii) in any event, terminate on the tenth
anniversary of the date of this Agreement.

            (g) If requested in writing by the underwriters for the initial
underwritten public offering of securities of the Company, each holder of
Restricted Stock shall agree not to sell publicly any shares of Restricted Stock
or any other shares of Common Stock (other than shares of Restricted Stock or
other shares of Common Stock being registered in such offering), without the
consent of such underwriters, for a period of not more than 180 days following
the effective date of the registration statement relating to such offering;
provided, however, that all persons entitled to registration rights with respect
to shares of Common Stock who are not parties to this Agreement, all other
persons selling shares of Common Stock in such offering, all persons (other than
persons otherwise party to this Agreement) holding in excess of 1% of the then
outstanding Common Stock of the Company (assuming the exercise or conversion of
all exercisable or convertible securities) and all executive officers and
directors of the Company shall also have agreed not to sell publicly their
Common Stock under the circumstances and pursuant to the terms set forth in this
Section 14(g).

            (h) Notwithstanding the provisions of Section 7(a), the Company's
obligation to file a registration statement pursuant to Section 4 or 6 hereof,
or cause such registration statement to become and remain effective, may be
suspended one time for a period not to exceed 90 days in any 18-month period if
there exists at the time material non-public information relating to the
Company, the disclosure of which, in the reasonable opinion of the Company,
would be detrimental to the Company.

            (i) Without the prior consent of the holders holding a majority of
the outstanding shares of Restricted Stock held by all of the holders, the
Company shall not grant to any third party any registration rights more
favorable than or inconsistent with any of those contained herein, so long as
any of the registration rights under this Agreement remains in effect.

            (j) If any provision of this Agreement shall be held to be illegal,
invalid or unenforceable, such illegality, invalidity or unenforceability shall
attach only to such provision and shall not in any manner affect or render
illegal, invalid or unenforceable any other provision of this Agreement, and
this Agreement shall be carried out as if any such illegal, invalid or
unenforceable provision were not contained herein.

            (k) In addition to any and all other remedies that may be available
at law in the event of any breach of this Agreement, each Purchaser shall be
entitled to specific performance of the agreements and obligations of the
Company hereunder and to such other injunctive or other equitable relief as may
be granted by a court of competent jurisdiction.

                                      -14-
<PAGE>

      IN WITNESS WHEREOF, this Agreement has been executed as of the day and
year first above written.

                                      COMPANY:

                                           EGENERA, INC.

                                           By: /s/ Vern J. Brownell
                                                Vern J. Brownell, President

                                      PURCHASERS:

                                           TCV IV, L.P.
                                           a Delaware limited partnership
                                           By: Technology Crossover Management
                                           IV, L.L.C.
                                           Its:  General Partner

                                           By: /s/ Robert Bensky
                                               ---------------------------------
                                               Name: Robert Bensky
                                                   Attorney-in-Fact

                                           TCV IV STRATEGIC PARTNERS, L.P.
                                           a Delaware limited partnership
                                           By: Technology Crossover Management
                                           IV, L.L.C.
                                           Its: General Partner

                                           By: /s/ Robert Bensky
                                               ---------------------------------
                                               Name: Robert Bensky
                                                     Attorney-in-Fact

                                           Kodiak Venture Partners

                                           By: Kodiak Ventures Management,
                                              L.P., its General Partner
                                           By: Kodiak Ventures Management
                                               Company, Inc.,
                                               its General Partner

                                           By: /s/ Louis J. Volpe
                                               ---------------------------------
                                               Name:
                                               Title:

   SIGNATURE PAGE TO THIRD AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

<PAGE>

                                           Austin Ventures VII, L.P.

                                           By: /s/ Basil Horganic
                                               ---------------------------------
                                               Name: Basil Horganic
                                               Title: Partner

                                               Austin Ventures VIII, L.P.

                                           By: /s/ Basil Horganic
                                               ---------------------------------
                                               Name: Basil Horganic
                                               Title: Partner

                                           Spectrum Equity Investors IV, L.P.
                                           By: Spectrum Equity Associates
                                               IV, L.P., its General Partner

                                           By: /s/ illegible
                                               ---------------------------------
                                               Name:
                                               Title:

                                           Spectrum Equity Investors Parallel
                                           IV, L.P.
                                           By: Spectrum Equity Associates
                                               IV, L.P., its General Partner

                                           By: /s/ illegible
                                               ---------------------------------
                                               Name:
                                               Title:

                                           Spectrum IV Investment Managers'
                                           Fund, L.P.

                                           By: /s/ illegible
                                               ---------------------------------
                                               Name:
                                               Title:

   SIGNATURE PAGE TO THIRD AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT
<PAGE>

                         YANKEETEK INCUBATOR FUND, L.P.
                         By: YankeeTek Partners, L.P., its General Partner
                         By: YTI, LLC, its General Partner

                         By:   /s/ Howard Anderson
                             ------------------------------------------------
                             Name: Howard Anderson
                             Managing Member

                         YANKEETEK AFFILIATE FUND, L.P.
                         By: YankeeTek Partners, L.P., its General Partner
                         By: YTI, LLC, its General Partner

                         By:   /s/ Howard Anderson
                             ------------------------------------------------
                             Name: Howard Anderson
                             Managing Member

                         YANKEETEK INVESTMENT PARTNERS, L.L.C.

                         By:   /s/ Howard Anderson
                             ------------------------------------------------
                             Name: Howard Anderson
                             Managing Member

   SIGNATURE PAGE TO THIRD AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

<PAGE>

                         Credit Suisse First Boston Equity Partners, L.P.
                         By: Hemisphere Private Equity Partners Ltd., its
                             General Partner

                         By:   /s/ Kenneth J. Lohsen
                             ------------------------------------------------
                             Kenneth J. Lohsen
                             Attorney-in-Fact

                         Credit Suisse First Boston Equity Partners
                             (Bermuda), L.P.
                         By: Hemisphere Private Equity Partners Ltd., its
                             General Partner

                         By:   /s/ Kenneth J. Lohsen
                             ------------------------------------------------
                             Kenneth J. Lohsen
                             Attorney-in-Fact

                         Credit Suisse First Boston U.S. Executive
                         Advisors, L.P.
                         By: Hemisphere Private Equity Partners Ltd., its
                             General Partner

                         By: /s/ Kenneth J. Lohsen
                             ------------------------------------------------
                             Kenneth J. Lohsen
                             Attorney-in-Fact

                         Credit Suisse First Boston Finders and
                         Screeners, L.P.
                         By: Merchant Capital Inc., its General Partner

                         By:   /s/ Kenneth J. Lohsen
                             ------------------------------------------------
                             Kenneth J. Lohsen
                             Vice President

                         EMA Private Equity Fund 2000, L.P.
                         By: Credit Suisse First Boston (Bermuda) Limited, its
                             General Partner

                         By:   /s/ Kenneth J. Lohsen
                             ------------------------------------------------
                             Kenneth J. Lohsen
                             Vice President

   SIGNATURE PAGE TO THIRD AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

<PAGE>

                         EMA Partners Fund 2000, L.P.
                         By: Credit Suisse First Boston (Bermuda) Limited, its
                             General Partner

                         By:   /s/ Kenneth J. Lohsen
                             ------------------------------------------------
                             Kenneth J. Lohsen
                             Vice President

   SIGNATURE PAGE TO THIRD AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

<PAGE>

                         Crosslink Ventures IV, L.P.
                         By: Crosslink Omega IV Holdings, L.L.C.,
                             its General Partner

                         By:   /s/ Michael J. Stark
                             ------------------------------------------------
                             Michael J. Stark, Managing Member

                         Offshore Crosslink Omega Ventures IV
                         (a Cayman Islands Unit Trust)
                         By: Crosslink Omega IV Holdings, L.L.C.,
                             Authorized Signatory

                         By:   /s/ Michael J. Stark
                             ------------------------------------------------
                             Michael J. Stark, Managing Member

                         Crosslink Omega Ventures IV GmbH & Co. KG
                         By: Crosslink Verwaltungs GmbH,
                             General Partner

                         By:   /s/ Michael J. Stark
                             ------------------------------------------------
                             Michael J. Stark, Managing Director

                         Omega Bayview IV, L.L.C.

                         By:   /s/ Michael J. Stark
                             ------------------------------------------------
                             Michael J. Stark, Authorized Signatory

                         Crosslink Crossover Fund III, L.P.
                         By: Crossover Fund III Management, L.L.C.,
                             Its General Partner

                         By:   /s/ Michael J. Stark
                             ------------------------------------------------
                             Michael J. Stark, Managing Member

                         Crosslink Crossover Fund IV, L.P.
                         By: Crossover Fund IV Management, L.L.C.,
                             Its General Partner

                         By:   /s/ Michael J. Stark
                             ------------------------------------------------
                             Michael J. Stark, Managing Member

   SIGNATURE PAGE TO THIRD AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

<PAGE>

                         Offshore Crosslink Crossover Fund III, Unit Trust
                         By: Crossover Fund III Management, L.L.C.,
                             Authorized Signatory

                         By:   /s/ Michael J. Stark
                             ------------------------------------------------
                             Michael J. Stark, Managing Member

                         /s/ illegible
                         --------------------------------------------
                         Robin Neustein

                         ZOLOT CAPITAL PARTNERS LLC

                         By:   /s/ illegible
                             ------------------------------------------------
                         Kenneth Zolot, its Manager

   SIGNATURE PAGE TO THIRD AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

<PAGE>

                         THE GOLDMAN SACHS GROUP, INC.

                         By:   /s/ John E. Bowman
                             ------------------------------------------------
                             Name: John E. Bowman
                             Title: Attorney-in-Fact

                         STONE STREET FUND 2000, L.P.
                         By: Stone Street 2000, L.L.C., its General Partner

                         By:   /s/ John E. Bowman
                             ------------------------------------------------
                             Name: John E. Bowman
                             Title: Vice President

                         GOLDMAN SACHS DIRECT INVESTMENT FUND 2000, L.P.
                         By: GS Employee Funds 2000 GP, L.L.C.
                             Its General Partner

                         By:   /s/ John E. Bowman
                             ------------------------------------------------
                             Name: John E. Bowman
                             Title: Vice President

                         GS PEP Technology Fund 2000, L.P.
                         By: GS PEP Tech 2000 Advisors, L.L.C., its
                             General Partner
                         By: GSAM Gen - Par, L.L.C., its Managing Member

                         By:   /s/ J. Barbetta
                             ------------------------------------------------
                             Name: Jennifer Barbetta
                             Title: Authorized Signatory

                         GS PEP Technology Fund 2000 Offshore Holdings, L.P.
                         By: GS PEP Tech 2000 Offshore Holdings
                             Advisors, Inc., its General Partner

                         By:   /s/ J. Barbetta
                             ------------------------------------------------
                             Name: Jennifer Barbetta
                             Title: Authorized Signatory

   SIGNATURE PAGE TO THIRD AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

<PAGE>

                         Stone Street PEP Technology Fund 2000, L.P.
                         By: Stone Street PEP Technology 2000, L.L.C.,
                             its General Partner

                         By:   /s/ J. Barbetta
                             ------------------------------------------------
                             Name: Jennifer Barbetta
                             Title: Authorized Signatory

                         GS Private Equity Partners 1999 - Direct Investment
                         Fund, L.P.
                         By: GS PEP 1999 Direct Investment Advisors, L.L.C.,
                             its General Partner
                         By: GSAM Gen-Par, L.L.C., its Managing Member

                         By:   /s/ J. Barbetta
                             ------------------------------------------------
                             Name: Jennifer Barbetta
                             Title: Authorized Signatory

   SIGNATURE PAGE TO THIRD AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

<PAGE>

                         LEHMAN BROTHERS VENTURE CAPITAL PARTNERS II, L.P.
                         By: Lehman Brothers Venture Associates II LLC, its
                             General Partner

                         By:   /s/ illegible
                             ------------------------------------------------
                             Name: illegible
                             Title:

                         LEHMAN BROTHERS P.A. LLC

                         By:   /s/ illegible
                             ------------------------------------------------
                             Name: illegible
                             Title:

                         LEHMAN BROTHERS PARTNERSHIP ACCOUNT 2000/2001, L.P.
                         By: Lehman Brothers Partnership GP 2000/2001, L.P., its
                             General Partner
                         By: LB I Group Inc., its General Partner

                         By:   /s/ illegible
                             ------------------------------------------------
                             Name: illegible
                             Title:

                         LEHMAN BROTHERS OFFSHORE PARTNERSHIP ACCOUNT
                         2000/2001, L.P.
                         By: Lehman Brothers Offshore Partnership GP 2000/2001,
                             L.P., its General Partner
                         By: Lehman Brothers Offshore Partners Ltd., its General
                             Partner

                         By:   /s/ illegible
                             ------------------------------------------------
                             Name: illegible
                             Title:

                         LEHMAN BROTHERS VC PARTNERS 2002, L.P.

                         By:   /s/ illegible
                             ------------------------------------------------
                             Name: illegible
                             Title:

   SIGNATURE PAGE TO THIRD AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT
<PAGE>

                                   SCHEDULE I

                                   Purchasers

Austin Ventures VII, L.P.

Austin Ventures VIII, L.P.

Credit Suisse First Boston Equity Partners (Bermuda), L.P.

Credit Suisse First Boston Equity Partners, L.P.

Credit Suisse First Boston Finders and Screeners, L.P.

Credit Suisse First Boston U.S. Executive Advisors, L.P.

CROSSLINK CROSSOVER FUND III, L.P.

CROSSLINK CROSSOVER FUND IV, L.P.

CROSSLINK OMEGA VENTURES IV GmbH & Co. KG

CROSSLINK VENTURES IV, L.P.

EMA Partners Fund 2000, L.P.

EMA Private Equity Fund 2000, L.P.

Frank Fanzilli

Goldman Sachs Direct Investment Fund 2000, L.P.

GS PEP Technology Fund 2000 Offshore Holdings, L.P.

GS PEP Technology Fund 2000, L.P.

GS Private Equity Partners 1999 - Direct Investment Fund, L.P.

Harry Copperman

Jacob Goldfield

James I. and Clemmie Cash, Trustees of the James I. and Clemmie Cash Jr., PhD,
PSRP

Kenneth Zolot

Kodiak Venture Partners

Lehman Brothers Offshore Partnership Account 2000/2001, L.P

Lehman Brothers P.A. LLC

Lehman Brothers Partnership Account 2000/2001, L.P.

Lehman Brothers VC Partners 2002, L.P.

Lehman Brothers Venture Capital Partners II, L.P.

   SIGNATURE PAGE TO THIRD AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

<PAGE>

Mizuho Capital Company

OFFSHORE CROSSLINK CROSSOVER FUND III, Unit Trust

OFFSHORE CROSSLINK OMEGA VENTURES IV (a Cayman Islands Unit Trust)

OMEGA BAYVIEW IV, L.L.C.

Robin Neustein

Spectrum Equity Investors IV, L.P.

Spectrum Equity Investors Parallel IV, L.P.

Spectrum IV Investment Managers' Fund, L.P.

Stone Street Fund 2000, L.P.

Stone Street PEP Technology Fund 2000, L.P.

TCV IV, L.P.

TCV IV Strategic Partners, L.P.

The Goldman Sachs Group, Inc.

UBS Capital Americas II, LLC

Volpe Family Limited Partnership

YankeeTek Affiliate Fund, LP

YankeeTek Incubator Fund, LP

YankeeTek Investment Partners, LLC

Zolot Capital Partners LLC

                                       26
<PAGE>

                                 AMENDMENT NO. 1
                                       TO
                           THIRD AMENDED AND RESTATED
                          REGISTRATION RIGHTS AGREEMENT

      THIS AMENDMENT NO. 1 TO THIRD AMENDED AND RESTATED REGISTRATION RIGHTS
AGREEMENT (this "Amendment") is made as of December 22, 2003 by and among
Egenera, Inc., a Delaware corporation (the "Company"), and the persons listed as
Purchasers in Schedule I to the Third Amended and Restated Registration Rights
Agreement, dated as of December 22, 2003 (the "Original Agreement").

                                    Recitals

      A.    The Company and the Purchasers are parties to the Original
Agreement.

      B.    The Company and the Purchasers desire to amend, in accordance with
Section 14(d) of the Original Agreement, the Original Agreement as hereinafter
expressly provided.

      NOW, THEREFORE, the Company and the Purchasers agree as follows:

      1.    Capitalized terms used herein without definition have the same
meanings as in the Original Agreement.

      2.    The definition of "Restricted Stock" set forth in Section 1 of the
Original Agreement is hereby amended by deleting such definition in its entirety
and substituting therefor the following definition:

                  "Restricted Stock" shall mean (i) the Conversion Shares, (ii)
      any shares of Common Stock (or shares of Common Stock issued upon
      conversion of any securities of the Company) purchased by Crosslink, TCV,
      or any Investor Affiliates in a private placement as contemplated by
      Section 2 of that certain Amended and Restated IPO Allocation Agreement
      dated as of the date hereof (the "IPO Allocation Agreement") between the
      Company, Crosslink Capital, Inc. and TCV ("Allocation Agreement Shares"),
      (iii) solely in connection with a Follow-on Offering (as defined in
      Section 1(j) of the IPO Allocation Agreement), shares of Common Stock
      purchased by Crosslink, TCV, or any Investor Affiliates pursuant to
      Section 1 of the IPO Allocation Agreement, and (iv) any shares of the
      Company's Common Stock acquired by (A) Crosslink, TCV and/or any Investor
      Affiliates or (B) GS PEP Technology Fund 2000, L.P., GS PEP Technology
      Fund 2000 Offshore Holdings, L.P., Stone Street PEP Technology Fund 2000,
      L.P., GS Private Equity Partners 1999 - Direct Investment Fund, L.P.,
      YankeeTek Affiliate Fund, LP, YankeeTek Incubator Fund, LP, Zolot Capital
      Partners LLC and/or

                                       27
<PAGE>

      any of their respective affiliates, from any currently existing holder of
      the Company's Common Stock on or prior to February 27, 2004, but excluding
      for purposes of clauses (i), (ii), (iii) and (iv) above, any shares of
      capital stock of the Company which have been (a) registered under the
      Securities Act pursuant to an effective registration statement filed
      thereunder and disposed of in accordance with the registration statement
      covering them or (b) publicly sold pursuant to Rule 144 under the
      Securities Act.

      3.    Except as expressly amended hereby, the Original Agreement shall
continue in full force and effect as heretofore in effect.

      4.    This Amendment may be executed in two or more counterparts, each of
which shall be deemed an original, but all of which together shall constitute
one and the same instrument.

        [The remainder of this page has been intentionally left blank.]

                                       28
<PAGE>

      IN WITNESS WHEREOF, this Amendment has been executed as of the day and
year first above written.

                                 COMPANY:

                                 EGENERA, INC.

                                 By: /s/ Timothy Lindamood
                                     -------------------------------------------
                                     Name: Timothy M. Lindamood
                                     Title: Assistant Secretary and Director of
                                            Legal Affairs

                                 PURCHASERS:

                      SIGNATURE PAGE TO AMENDMENT NO. 1 TO
            THIRD AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

<PAGE>

                                 TCV IV, L.P.
                                 a Delaware limited partnership
                                 By:  Technology Crossover Management IV, L.L.C.
                                 Its: General Partner

                                 By:   /s/ Robert Bensky
                                     -------------------------------------------
                                 Name: Robert Bensky
                                       Attorney-in-Fact

                                 TCV IV STRATEGIC PARTNERS, L.P.
                                 a Delaware limited partnership
                                 By:  Technology Crossover Management IV, L.L.C.
                                 Its: General Partner

                                 By:   /s/ Robert Bensky
                                     -------------------------------------------
                                 Name: Robert Bensky
                                       Attorney-in-Fact

                                 Kodiak Venture Partners
                                 By: Kodiak Ventures Management, L.P., its
                                     General Partner
                                 By: Kodiak Ventures Management Company, Inc.,
                                     its General Partner

                                 By:   /s/ Louis J. Volpe
                                     -------------------------------------------
                                 Name:
                                 Title:

   SIGNATURE PAGE TO THIRD AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

<PAGE>

                                 Austin Ventures VII, L.P.

                                 By:   /s/ Basil Horganic
                                     -------------------------------------------
                                     Name: Basil Horganic
                                     Title: Partner

                                 Austin Ventures VIII, L.P.

                                 By:   /s/ Basil Horganic
                                     -------------------------------------------
                                      Name: Basil Horganic
                                      Title: Partner

                                 Spectrum Equity Investors IV, L.P.
                                 By: Spectrum Equity Associates IV, L.P., its
                                     General Partner

                                 By:   /s/ illegible
                                     -------------------------------------------
                                     Name:
                                     Title:

                                 Spectrum Equity Investors Parallel IV, L.P.
                                 By: Spectrum Equity Associates IV, L.P., its
                                     General Partner

                                 By:   /s/ illegible
                                     -------------------------------------------
                                     Name:
                                     Title:

                                 Spectrum IV Investment Managers' Fund, L.P.

                                 By: /s/ illegible
                                     -------------------------------------------
                                     Name:
                                     Title:

<PAGE>

                                 YANKEETEK INCUBATOR FUND, L.P.
                                 By: YankeeTek Partners, L.P., its General
                                     Partner
                                 By: YTI, LLC, its General Partner

                                 By: /s/ John Genest
                                     -------------------------------------------
                                     Name: John Genest
                                     Managing Member

                                 YANKEETEK AFFILIATE FUND, L.P.
                                 By: YankeeTek Partners, L.P., its General
                                     Partner
                                 By: YTI, LLC, its General Partner

                                 By: /s/ John Genest
                                     -------------------------------------------
                                     Name: John Genest
                                     Managing Member

                                 YANKEETEK INVESTMENT PARTNERS, L.L.C.

                                 By: /s/ John Genest
                                     -------------------------------------------
                                     Name: John Genest
                                     Managing Member

<PAGE>

                                 Credit Suisse First Boston Equity Partners,
                                 L.P.

                                 By: /s/ Kenneth Lohsen
                                     -------------------------------------------
                                     Name: Kenneth Lohsen
                                     Title: Authorized Signatory

                                 Credit Suisse First Boston Equity Partners
                                 (Bermuda), L.P.

                                 By: /s/ Kenneth Lohsen
                                     -------------------------------------------
                                     Name: Kenneth Lohsen
                                     Title: Authorized Signatory

                                 Credit Suisse First Boston U.S. Executive
                                 Advisors, L.P.

                                 By: /s/ Kenneth Lohsen
                                     -------------------------------------------
                                     Name: Kenneth Lohsen
                                     Title: Authorized Signatory

                                 Credit Suisse First Boston Finders and
                                 Screeners, L.P.

                                 By: /s/ Kenneth Lohsen
                                     -------------------------------------------
                                     Name: Kenneth Lohsen
                                     Title: Authorized Signatory

                                 EMA Private Equity Fund 2000, L.P.

                                 By: /s/ Kenneth Lohsen
                                     -------------------------------------------
                                     Name: Kenneth Lohsen
                                     Title: Authorized Signatory

                                 EMA Partners Fund 2000, L.P.

                                 By: /s/ Kenneth Lohsen
                                     -------------------------------------------
                                     Name: Kenneth Lohsen
                                     Title: Authorized Signatory

<PAGE>

                                 Crosslink Ventures IV, L.P.
                                 By: Crosslink Omega IV Holdings, L.L.C.,
                                     its General Partner

                                 By: /s/ Michael J. Stark
                                     -------------------------------------------
                                     Michael J. Stark, Managing Member

                                 Offshore Crosslink Omega Ventures IV
                                  (a Cayman Islands Unit Trust)
                                 By: Crosslink Omega IV Holdings, L.L.C.,
                                     Authorized Signatory

                                 By: /s/ Michael J. Stark
                                     -------------------------------------------
                                     Michael J. Stark, Managing Member

                                 Crosslink Omega Ventures IV GmbH & Co. KG
                                 By: Crosslink Verwaltungs GmbH,
                                     General Partner

                                 By: /s/ Michael J. Stark
                                     -------------------------------------------
                                     Michael J. Stark, Managing Director

                                 Omega Bayview IV, L.L.C.

                                 By: /s/ Michael J. Stark
                                     -------------------------------------------
                                     Michael J. Stark, Authorized Signatory

                                 Crosslink Crossover Fund III, L.P.
                                 By: Crossover Fund III Management, L.L.C.,
                                     Its General Partner

                                 By: /s/ Michael J. Stark
                                     -------------------------------------------
                                     Michael J. Stark, Managing Member

<PAGE>

                                 Crosslink Crossover Fund IV, L.P.
                                 By: Crossover Fund IV Management, L.L.C.,
                                     Its General Partner

                                 By: /s/ Michael J. Stark
                                     -------------------------------------------
                                     Michael J. Stark, Managing Member

                                 Offshore Crosslink Crossover Fund III, Unit
                                     Trust
                                 By: Crossover Fund III Management, L.L.C.,
                                     Authorized Signatory

                                 By: /s/ Michael J. Stark
                                     -------------------------------------------
                                     Michael J. Stark, Managing Member

                                 _______________________________________________
                                 Robin Neustein

                                 ZOLOT CAPITAL PARTNERS LLC

                                 By: /s/ illegible
                                     -------------------------------------------
                                 Kenneth Zolot, its Manager

<PAGE>

                                 THE GOLDMAN SACHS GROUP, INC.

                                 By: /s/ KB Enquist
                                     -------------------------------------------
                                     Name: Katherine B. Enquist
                                     Title: Attorney-in-Fact

                                 STONE STREET FUND 2000, L.P.
                                 By: Stone Street 2000, L.L.C., its General
                                     Partner

                                 By: /s/ KB Enquist
                                     -------------------------------------------
                                     Name: Katherine B. Enquist
                                     Title: Vice President

                                 GOLDMAN SACHS DIRECT INVESTMENT FUND 2000, L.P.
                                 By: GS Employee Funds 2000 GP, L.L.C.
                                     Its General Partner

                                 By: /s/ KB Enquist
                                     -------------------------------------------
                                     Name: Katherine B. Enquist
                                     Title: Vice President

                                 GS PEP Technology Fund 2000, L.P.
                                 By: GS PEP Tech 2000 Advisors, L.L.C., its
                                     General Partner
                                 By: GSAM Gen - Par, L.L.C., its Managing Member

                                 By: /s/ illegible
                                     -------------------------------------------
                                     Name: Leonard Nero
                                     Title: Authorized Signatory

                                 GS PEP Technology Fund 2000 Offshore Holdings,
                                 L.P.
                                 By: GS PEP Tech 2000 Offshore Holdings
                                     Advisors, Inc., its General Partner

                                 By: /s/ illegible
                                     -------------------------------------------
                                     Name: Leonard Nero
                                     Title: Authorized Signatory

<PAGE>

                                 Stone Street PEP Technology Fund 2000, L.P.
                                 By: Stone Street PEP Technology 2000, L.L.C.,
                                     its General Partner

                                 By: /s/ illegible
                                     -------------------------------------------
                                     Name: Leonard Nero
                                     Title: Authorized Signatory

                                 GS Private Equity Partners 1999 - Direct
                                 Investment Fund, L.P.
                                 By: GS PEP 1999 Direct Investment Advisors,
                                     L.L.C., its General Partner

                                 By: GSAM Gen-Par, L.L.C., its Managing Member

                                 By: /s/ illegible
                                     -------------------------------------------
                                     Name: Leonard Nero
                                     Title: Authorized Signatory

<PAGE>

                                 LEHMAN BROTHERS VENTURE CAPITAL PARTNERS II,
                                 L.P.
                                 By: Lehman Brothers Venture Associates II LLC,
                                     its General Partner

                                 By: /s/ illegible
                                     -------------------------------------------
                                     Name:
                                     Title:

                                 LEHMAN BROTHERS P.A. LLC

                                 By: /s/ illegible
                                     -------------------------------------------
                                     Name:
                                     Title:

                                 LEHMAN BROTHERS PARTNERSHIP ACCOUNT 2000/2001,
                                 L.P.
                                 By: Lehman Brothers Partnership GP 2000/2001,
                                     L.P., its General Partner
                                 By: LB I Group Inc., its General Partner

                                 By: /s/ illegible
                                     -------------------------------------------
                                     Name:
                                     Title:

                                 LEHMAN BROTHERS OFFSHORE PARTNERSHIP ACCOUNT
                                 2000/2001, L.P.
                                 By: Lehman Brothers Offshore Partnership GP
                                     2000/2001, L.P., its General Partner
                                 By: Lehman Brothers Offshore Partners Ltd.,
                                     its General Partner

                                 By: /s/ illegible
                                     -------------------------------------------
                                     Name:
                                     Title:

                                 LEHMAN BROTHERS VC PARTNERS 2002, L.P.

                                 By: /s/ illegible
                                     -------------------------------------------
                                     Name:
                                     Title:<PAGE>

                                                                   EXHIBIT 10.20

THIS WARRANT HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED OR ANY STATE SECURITIES LAWS. NO SALE OR DISPOSITION MAY BE EFFECTED
WITHOUT (i) EFFECTIVE REGISTRATION STATEMENTS RELATED THERETO, (ii)AN OPINION OF
COUNSEL OR OTHER EVIDENCE, REASONABLY SATISFACTORY TO THE COMPANY, THAT SUCH
REGISTRATIONS ARE NOT REQUIRED, (iii) RECEIPT OF NO-ACTION LETTERS FROM THE
APPROPRIATE GOVERNMENTAL AUTHORITIES, OR (iv) OTHERWISE COMPLYING WITH THE
PROVISIONS OF SECTION 7 OF THIS WARRANT.

                                 EGENERA, INC.

                       WARRANT TO PURCHASE 95,574 SHARES
                          OF SERIES B PREFERRED STOCK

      THIS CERTIFIES THAT, for value received, GATX VENTURES, INC. and its
permitted assignees are entitled to subscribe for and purchase 95,574 shares of
the fully paid and nonassessable Series B Convertible Preferred Stock (as
adjusted pursuant to Section 4 hereof, the "Shares") of EGENERA, INC., a
Delaware corporation (the "Company") at the price of $0.994 per share (such
price and such other price as shall result, from time to time, from the
adjustments specified in Section 4 hereof is herein referred to as the "Warrant
Price"), subject to the provisions and upon the terms and conditions hereinafter
set forth. As used herein, (a) the term "Series Preferred" shall mean the
Company's presently authorized Series B Convertible Preferred Stock, $0.001 par
value per share, and any stock into or for which such Series B Convertible
Preferred Stock may hereafter be converted or exchanged, and after the automatic
conversion of the Series B Convertible Preferred Stock to common stock shall
mean the Company's common stock, $0.001 par value per share (the "Common
Stock"), (b) the term "Date of Grant" shall mean December 13, 2001, and (c) the
term "Other Warrants" shall mean any other warrants issued by the Company in
connection with the transaction with respect to which this Warrant was issued,
and any warrant issued upon transfer or partial exercise of or in lieu of this
Warrant. The term "Warrant" as used herein shall be deemed to include Other
Warrants unless the context clearly requires otherwise.

      1.    Term. The purchase right represented by this Warrant is exercisable,
in whole or in part, at any time and from time to time from the Date of Grant
through the date which is ten (10) years after the Date of Grant.

      2.    Method of Exercise; Payment; Issuance of New Warrant. Subject to
Section 1 hereof, the purchase right represented by this Warrant may be
exercised by the holder hereof, in whole or in part and from time to time, at
the election of the holder hereof, by (a) the surrender of this Warrant (with
the notice of exercise substantially in the form attached hereto as Exhibit A-1
duly completed and executed) at the principal office of the Company and by the
payment to the Company, by certified or bank check, or by wire transfer of
immediately available funds to an account designated by the Company (a "Wire
Transfer") of an amount equal to the then applicable Warrant Price multiplied by
the number of Shares then being purchased; (b) if in connection with a
registered public offering of the Company's securities in which the holder has
the right to participate pursuant to Section 9, and then only with respect to
such number of shares as are eligible pursuant to the

<PAGE>

terms of Section 9 to be sold by the holder in such offering, the surrender of
this Warrant (with the notice of exercise form attached hereto as Exhibit A-2
duly completed and executed) at the principal office of the Company together
with notice of arrangements reasonably satisfactory to the Company for payment
to the Company either by certified or bank check or by Wire Transfer from the
proceeds of the sale of shares to be sold by the holder in such public offering
of an amount equal to the then applicable Warrant Price per share multiplied by
the number of Shares then being purchased; of (c) exercise of the "net issuance"
right provided for in Section 10.2 hereof. The person or persons in whose
name(s) any certificate(s) representing shares of Series Preferred shall be
issuable upon exercise of this Warrant shall be deemed to have become the
holder(s) of record of, and shall be treated for all purposes as the record
holder(s) of, the shares represented thereby (and such shares shall be deemed to
have been issued) immediately prior to the close of business on the date or
dates upon which this Warrant is exercised. In the event of any exercise of the
rights represented by this Warrant, certificates for the shares of stock so
purchased shall be delivered to the holder hereof as soon as possible and in any
event within thirty (30) days after such exercise and, unless this Warrant has
been fully exercised or expired, a new Warrant representing the portion of the
Shares, if any, with respect to which this Warrant shall not then have been
exercised shall also be issued to the holder hereof as soon as possible and in
any event within such thirty-day period; provided that at such time as the
Company is subject to the reporting requirements of the Securities Exchange Act
of 1934, as amended, if requested by the holder of this Warrant, the Company
shall cause its transfer agent to deliver the certificate representing Shares
issued upon exercise of this Warrant to a broker or other person (as directed by
the holder exercising this Warrant) within the time period required to settle
any trade made by the holder after exercise of this Warrant.

      3.    Stock Fully Paid; Reservation of Shares. All Shares that may be
issued upon the exercise of the rights represented by this Warrant will, upon
issuance pursuant to the terms and conditions herein, be fully paid and
nonassessable, and free from all preemptive rights and taxes, liens and charges
with respect to the issue thereof. During the period within which the rights
represented by this Warrant may be exercised, the Company will at all times have
authorized, and reserved for the purpose of the issue upon exercise of the
purchase rights evidenced by this Warrant, a sufficient number of shares of its
Series Preferred to provide for the exercise of the rights represented by this
Warrant and a sufficient number of shares of its Common Stock to provide for the
conversion of the Series Preferred into Common Stock.

      4.    Adjustment of Warrant Price and Number of Shares. The number and
kind of securities purchasable upon the exercise of this Warrant and the Warrant
Price shall be subject to adjustment from time to time upon the occurrence of
certain events, as follows:

            (a)   Reclassification or Merger. In case of any reclassification or
change of securities of the class issuable upon exercise of this Warrant (other
than a change in par value, or from par value to no par value, or from no par
value to par value, or as a result of a subdivision or combination), or in case
of any merger of the Company with or into another corporation (other than a
merger with another corporation in which the Company is the acquiring and the
surviving corporation and which does not result in any reclassification or
change of outstanding securities issuable upon exercise of this Warrant), or in
case of any sale of all or substantially all of the assets of the Company, the
Company, or such successor or purchasing corporation, as the case may be,

                                      -2-
<PAGE>

shall, at its option, either (i) duly execute and deliver to the holder of this
Warrant a new Warrant (in substantially the same form of this Warrant or in form
and substance reasonably satisfactory to the holder of this Warrant), or (ii)
make appropriate provision without the issuance of a new Warrant, so that the
holder of this Warrant shall have the right to receive upon exercise of this
Warrant, at a total purchase price not to exceed that payable upon the exercise
of the unexercised portion of this Warrant, and in lieu of the shares of Series
Preferred theretofore issuable upon exercise of this Warrant, the kind and
amount of shares of stock, other securities, money and property receivable upon
such reclassification, change, merger or sale by a holder of the number of
shares of Series Preferred then purchasable under this Warrant. Any new Warrant
shall provide for adjustments that shall be as nearly equivalent as may be
practicable to the adjustments provided for in this Section 4. The provisions of
this Section 4(a) shall similarly apply to successive reclassifications,
changes, mergers and sales and shall be made without duplication of any change
required pursuant to Section 4(b) or Section 4(c).

            (b)   Subdivision or Combination of Shares. If the Company at any
time while this Warrant remains outstanding and unexpired shall subdivide or
combine its outstanding shares of Series Preferred, the Warrant Price shall be
proportionately decreased and the number of Shares issuable hereunder shall be
proportionately increased in the case of a subdivision and the Warrant Price
shall be proportionately increased and the number of Shares issuable hereunder
shall be proportionately decreased in the case of a combination.

            (c)   Stock Dividends and Other Distributions. If the Company at any
time while this Warrant is outstanding and unexpired shall (i) pay a dividend
with respect to Series Preferred payable in Series Preferred, then the Warrant
Price shall be adjusted, from and after the date of determination of
shareholders entitled to receive such dividend or distribution, to that price
determined by multiplying the Warrant Price in effect immediately prior to such
date of determination by a fraction (A) the numerator of which shall be the
total number of shares of Series Preferred Outstanding immediately prior to such
dividend or distribution, and (B) the denominator of which shall be the total
number of shares of Series Preferred outstanding immediately after such dividend
or distribution; or (ii) make any other distribution with respect to Series
Preferred (except any distribution specifically provided for in Sections 4(a)
and 4(b)), then, in each such case, provision shall be made by the Company such
that the holder of this Warrant shall receive upon exercise of this Warrant a
proportionate share of any such dividend or distribution as though it were the
holder of the Series Preferred as of the record date fixed for the determination
of the shareholders of the Company entitled to receive such dividend or
distribution.

            (d)   Adjustment of Number of Shares. Upon each adjustment in the
Warrant Price pursuant to Section 4 and without duplication of any other
adjustment required hereunder, the number of Shares of Series Preferred
purchasable hereunder shall be adjusted, to the nearest whole share, to the
product obtained by multiplying the number of Shares purchasable immediately
prior to such adjustment in the Warrant Price by a fraction, the numerator of
which shall be the Warrant Price immediately prior to such adjustment and the
denominator of which shall be the Warrant Price immediately thereafter.

                                      -3-
<PAGE>

            (e)   Antidilution Rights. The other antidilution rights applicable
to the Shares of Series Preferred purchasable hereunder are set forth in the
Company's Certificate of Incorporation, as amended through the Date of Grant, a
true and complete copy of which is attached hereto as Exhibit B (as the same may
be further amended and in effect from time to time, the "Charter"). Such
antidilution rights shall not be restated, amended, modified or waived in any
manner that is adverse to the holder hereof without such holder's prior written
consent if the effect of such restatement, amendment, modification or waiver on
the holder hereof would be more adverse to the holder hereof than its effect on
the other holders of the Company's Series Preferred. The Company shall
promptly provide the holder hereof with any restatement, amendment, modification
or waiver of the Charter promptly after the same has been made.

      5.    Notice of Adjustments. Whenever the Warrant Price or the number of
Shares purchasable hereunder shall be adjusted pursuant to Section 4 hereof, the
Company shall make a certificate signed by its chief financial officer setting
forth, in reasonable detail, the event requiring the adjustment, the amount of
the adjustment, the method by which such adjustment was calculated, and the
Warrant Price and the number of Shares purchasable hereunder after giving effect
to such adjustment, and shall cause copies of such certificate to be mailed
(without regard to Section 13 hereof, by first class mail, postage prepaid) to
the holder of this Warrant. In addition, whenever the conversion price or
conversion ratio of the Series Preferred shall be adjusted, the Company shall
make a certificate signed by its chief financial officer setting forth, in
reasonable detail, the event requiring the adjustment, the amount of the
adjustment, the method by which such adjustment was calculated, and the
conversion price or ratio of the Series Preferred after giving effect to such
adjustment, and shall cause copies of such certificate to be mailed (without
regard to Section 13 hereof, by first class mail, postage prepaid) to the holder
of this Warrant; provided that any certificate delivered by the Company to the
holder of this Warrant in accordance with the Charter containing substantially
the same information shall be deemed compliance with the foregoing notice
required by this sentence.

      6.    Fractional Shares. No fractional shares of Series Preferred will be
issued in connection with any exercise hereunder, but in lieu of such fractional
shares the Company shall make a cash payment therefor based on the fair market
value of the Series Preferred on the date of exercise as reasonably determined
in good faith by the Company's Board of Directors.

      7.    Compliance with Act; Disposition of Warrant or Shares of Series
Preferred.

            (a)   Compliance with Act. The holder of this Warrant, by acceptance
hereof, agrees mat this Warrant, and the shares of Series Preferred to be issued
upon exercise hereof and any Common Stock issued upon conversion thereof are
being acquired for investment and that such holder will not offer, sell,
transfer, pledge or hypothecate or otherwise dispose of this Warrant, or any
shares of Series Preferred to be issued upon exercise hereof or any Common Stock
issued upon conversion thereof except under circumstances which will not result
in a violation of the Securities Act of 1933, as amended (the "Act") or any
applicable state securities laws. Upon exercise of this Warrant, unless the
Shares or shares of Common Stock being acquired are registered under the Act and
any applicable state securities laws the holder hereof shall confirm in writing
that the shares of Series Preferred so purchased (and any shares of Common Stock
issued upon conversion thereof) are

                                      -4-
<PAGE>

being acquired for investment and not with a view toward distribution or resale
in violation of the Act and shall confirm such other matters related thereto as
may be reasonably requested by the Company. This Warrant and all shares of
Series Preferred issued upon exercise of this Warrant and all shares of Common
Stock issued upon conversion thereof (unless registered under the Act and any
applicable state securities laws) shall be stamped or imprinted with a legend in
substantially the following form:

"THE SECURITIES EVIDENCED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES
ACT OF 1933, AS AMENDED, OR ANY STATE SECURITIES LAWS. NO SALE OR DISPOSITION
MAY BE EFFECTED WITHOUT (i) EFFECTIVE REGISTRATION STATEMENTS RELATED THERETO,
(ii) AN OPINION OF COUNSEL OR OTHER EVIDENCE, REASONABLY SATISFACTORY TO THE
COMPANY, THAT SUCH REGISTRATIONS ARE NOT REQUIRED, (iii) RECEIPT OF NO-ACTION
LETTERS FROM THE APPROPRIATE GOVERNMENTAL AUTHORITIES, OR (iv) OTHERWISE
COMPLYING WITH THE PROVISIONS OF SECTION 7 OF THE WARRANT UNDER WHICH THESE
SECURITIES WERE ISSUED, DIRECTLY OR INDIRECTLY."

      Said legend shall be removed by the Company, upon the request of a holder,
at such time as the restrictions on the transfer of the applicable security
shall have terminated. In addition, in connection with the issuance of this
Warrant, the bolder specifically represents to the Company by acceptance of this
Warrant as follows:

                  (1)   The holder is aware of the Company's business affairs
and financial condition, and has acquired information about the Company
sufficient to reach an informed and knowledgeable decision to acquire this
Warrant and has had such opportunity as such holder has deemed adequate to
obtain from representatives of the Company such information as such holder has
deemed necessary to permit the holder to evaluate the merits and risks of its
investment in the Company. The holder is acquiring this Warrant and any
underlying Shares or Common Stock for its own account for investment purposes
only and not with a view to, or for the resale in connection with, any
"distribution" thereof in violation of the Act.

                  (2)   The holder understands that this Warrant and any
underlying Shares or Common Stock have not been registered under the Act in
reliance upon a specific exemption therefrom, which exemption depends upon,
among other things, the bona fide nature of the holder's investment intent as
expressed herein.

                  (3)   The holder further understands that this Warrant and any
underlying Shares or Common Stock must be held indefinitely unless subsequently
registered under the Act and qualified under any applicable state securities
laws, or unless exemptions from registration and qualification are otherwise
available. The holder is able to bear the economic risk of holding this Warrant
and any underlying Shares or Common Stock as may be acquired upon exercise of
this Warrant for an indefinite period. The holder is aware of the provisions of
Rule 144, promulgated under the Act. The holder understands that this Warrant,
the Shares acquired pursuant to the exercise of this Warrant and the Common
Stock into which such Shares are convertible will be "restricted securities"
within the meaning of Rule 144 under the Act and that the exemption from
registration under Rule 144 will not be available for at least one year from the
date of the Warrant

                                      -5-
<PAGE>

with respect to any resale of this Warrant and from the date of exercise of this
Warrant with respect to any resale of the Shares or Common Stock into which such
Shares are convertible, and even then will not be available unless a public
market then exists for the stock of the Company, adequate information concerning
the Company is then available to the public, and other terms and conditions of
Rule 144 are complied with. Except as described in Section 9, the Company shall
be under no obligation to register this Warrant, the Shares or any shares of
Common Stock issuable upon conversion thereof.

                  (4)   The holder is an "accredited investor" as such term is
defined in Rule 501 of Regulation D promulgated under the Act.

            (b)   Disposition of Warrant or Shares. With respect to any offer,
sale or other disposition of this Warrant or any shares of Series Preferred
acquired pursuant to the exercise of this Warrant, or any shares of Common Stock
issuable upon conversion of Series Preferred, prior to registration of such
Warrant, Series Preferred or Common Stock shares, the holder hereof agrees to
give written notice to the Company prior thereto, describing briefly the manner
thereof, together with a written opinion of such holder's counsel, or other
evidence, if reasonably satisfactory to the Company, to the effect that such
offer, sale or other disposition may be effected without registration or
qualification (under the Act as then in effect or any federal or state
securities law then in effect) of this Warrant or such shares of Series
Preferred or Common Stock and indicating whether or not under the Act
certificates for this Warrant or such shares of Series Preferred or Common Stock
to be sold or otherwise disposed of require any restrictive legend as to
applicable restrictions on transferability in order to ensure compliance with
such law. Upon receiving such written notice and reasonably satisfactory opinion
or other evidence, the Company, as promptly as practicable but no later than
thirty (30) days after receipt of the written notice, shall notify such holder
that such holder may sell or otherwise dispose of this Warrant or such shares of
Series Preferred or Common Stock, all in accordance with the terms of the notice
delivered to the Company. If a determination has been made pursuant to this
Section 7(b) that the opinion of counsel for the holder or other evidence is not
reasonably satisfactory to the Company, the Company shall so notify the holder
promptly with details thereof after such determination has been made.
Notwithstanding the foregoing, this Warrant or such shares of Series Preferred
or Common Stock may, as to such federal laws, be offered, sold or Otherwise
disposed of in accordance with Rule 144 or 144A under the Act, provided that the
Company shall have been furnished with such information as the Company may
reasonably request to provide a reasonable assurance that the provisions of Rule
144 or 144A have been satisfied. Each certificate representing this Warrant or
the shares of Series Preferred or Common Stock thus transferred (except a
transfer pursuant to Rule 144 or 144A) shall bear a legend as to the applicable
restrictions on transferability in order to ensure compliance with such laws,
unless in the aforesaid opinion of counsel for the holder, such legend is not
required in order to ensure compliance with such laws. The Company may issue
stop transfer instructions to its transfer agent in connection with such
restrictions.

            (c)   Applicability of Restrictions. Neither any restrictions of any
legend described in this Warrant nor the requirements of Section 7(b) above
shall apply to any transfer of, or grant of a security interest in, this Warrant
(or the Series Preferred or Common Stock obtainable upon exercise thereof) or
any part hereof (i) to a partner of the holder if the holder is a partnership or
to a

                                      -6-
<PAGE>

member of the holder if the holder is a limited liability company, (ii) to a
partnership of which the holder is a partner or to a limited liability company
of which the holder is a member, or (iii) to any affiliate (as such term is
defined in Rule 501(b) of Regulation D promulgated under the Act) of the holder
if the holder is a corporation; provided that in any transfer of this Warrant,
Shares or Common Stock, if applicable, the transferee shall on the Company's
request agree in writing to be bound by the terms of this Warrant as if an
original holder hereof and represent in writing that the transferee is acquiring
the Warrant, Shares or Common Stock for its own account for investment purposes
and without any view towards distribution thereof and is an "accredited
investor" as such term is defined in Rule 501 of Regulation D promulgated under
the Act.

      8.    Rights as Shareholders; Information. No holder of this Warrant, as
such, shall be entitled to vote or receive dividends or be deemed the holder of
Series Preferred or any other securities of the Company which may at any time be
issuable upon the exercise hereof for any purpose, nor shall anything contained
herein be construed to confer upon the holder of this Warrant, as such, any of
the rights of a shareholder of the Company or any right to vote for the election
of directors or upon any matter submitted to shareholders at any meeting
thereof, or to receive notice of meetings, or to receive dividends or
subscription rights or otherwise until this Warrant shall have been exercised
and the Shares purchasable upon the exercise hereof shall have become
deliverable, as provided herein. Notwithstanding the foregoing, the Company will
transmit to the holder of this Warrant such information, documents and reports
as are generally distributed to the holders of Series Preferred concurrently
with the distribution thereof to such shareholders.

      9.    Registration Rights.

      (a)   Certain Definitions. As used in this Section 9, the following terms
shall have the following respective meanings:

      "Commission" shall mean the Securities and Exchange Commission, or any
other federal agency at the time administering the Act.

      "Exchange Act" shall mean the Securities Exchange Act of 1934, as amended.

      "Holders" shall mean the initial holder of this Warrant and any party to
which the registration rights described in this Section 9 are transferred
pursuant to Section 9(h)(i).

      "Restricted Stock" shall mean the shares of Common Stock issued upon
conversion of the Shares, excluding such shares of Common Stock that have been
(a) registered under the Act pursuant to an effective registration statement
filed thereunder and disposed of in accordance with the registration statement
covering them or (b) publicly sold pursuant to Rule 144 under the Act.

      "Rights Agreement" shall mean that certain Amended and Restated
Registration Rights Agreement dated as of July 16,2001 among the Company and
certain investors named therein (including any security holders of the Company
that may become additional parties thereto after the date hereof), as in effect
on the date hereof and as the same may be amended, restated, replaced or
otherwise modified and in effect from time to time after the date hereof.

                                      -7-
<PAGE>

      (b)   Registration. If the Company at any time (i) proposes to register
any of its securities under the Act for sale to the public, whether for its own
account or for the account of other security holders or both (except with
respect to registration statements on Forms S-4, S-8 or another form not
available for registering the Restricted Stock for sale to the public), or (ii)
is requested or required to register any such securities pursuant to Section 4
or Section 6 of the Rights Agreement, each such time it will give written notice
to the Holder(s) of its intention so to do. Upon the written request of any such
Holder, received by the Company within thirty (30) days after the giving of any
such notice by the Company, to register any of its Restricted Stock, the Company
will use commercially reasonable to cause the Restricted Stock as to which
registration shall have been so requested to be included in the securities to be
covered by the registration statement proposed or required to be filed by the
Company, all to the extent requisite to permit the sale or other disposition by
such Holder of such Restricted Stock so registered. In the event that any
registration pursuant to this Section 9(b) shall be, in whole or in part, an
underwritten public offering of Common Stock, the number of shares of Restricted
Stock to be included in such an underwriting may be reduced (pro rata among the
selling Holders and all other holder of shares requested to be included in such
underwriting by parties having been granted registration rights by the Company,
based upon the number of shares to be included in such underwriting owned by
such parties) if and to the extent that the managing underwriter shall be of the
opinion that such inclusion would adversely affect the marketing of the
securities to be sold by the Company therein; provided that such number of
shares sought to be included by the selling Holders and such holder of any Other
Warrant shall be reduced in their entirety before the number of shares of
Company securities sought to be registered by the parties to the Rights
Agreement is reduced. Notwithstanding the foregoing provisions, the Company may
withdraw any registration statement referred to in this Section 9 without
thereby incurring any liability to the holders of Restricted Stock.

      (c)   Registration Procedures. If and whenever the Company is required by
the provisions of Section 9(b) to use commercially reasonable to effect the
registration of any shares of Restricted Stock under the Act, the Company will,
as expeditiously as possible:

            (i)   prepare and file with the Commission a registration statement
with respect to such securities and use commercially reasonable to cause such
registration statement to become and remain effective for the period of the
distribution contemplated thereby (determined as hereinafter provided);

            (ii)  prepare and file with the Commission such amendments and
supplements to such registration statement and the prospectus used in connection
therewith as may be necessary to keep such registration statement effective for
the period specified in Section 9(c)(i) and comply with the provisions of the
Act with respect to the disposition of all Restricted Stock covered by such
registration statement in accordance with the sellers' intended method of
disposition set forth in such registration statement for such period;

            (iii) furnish to each selling Holder and to each underwriter such
number of copies of the registration statement and the prospectus included
therein (including each preliminary prospectus and amendment thereto) as such
persons reasonably may request in order to facilitate the public sale or other
disposition of the Restricted Stock covered by such registration statement;

                                      -8-
<PAGE>

            (iv)  use commercially reasonable to register or qualify the
Restricted Stock covered by such registration statement under the securities or
"blue sky" laws of such jurisdictions as the sellers of Restricted Stock or, in
the case of an underwritten public offering, the managing underwriter reasonably
shall request; provided that the Company shall not for any such purpose be
required to qualify generally to transact business as a foreign corporation in
any jurisdiction where it is not so qualified or to consent to general service
of process in any such jurisdiction;

            (v)   use commercially reasonable to list the Restricted Stock
covered by such registration statement with any securities exchange on which the
Common Stock of the Company is then listed;

            (vi)  immediately notify each selling Holder and each underwriter
under such registration statement, at any time when a prospectus relating
thereto is required to be delivered under the Act, of the happening of any event
of which the Company has knowledge as a result of which the prospectus contained
in such registration statement, as then in effect, includes an untrue statement
of a material fact or omits to state a material fact required to be stated
therein or necessary to make the statements therein not misleading in light of
the circumstances then existing, and each Holder hereby covenants and agrees,
upon receipt of such notification, to discontinue disposition of Restricted
Stock pursuant to such registration statement until the time of effectiveness of
an amendment thereto or a supplement to such prospectus included therein as may
be necessary so that, as thereafter delivered to the purchasers of such
Restricted Stock, such prospectus shall not include an untrue statement of a
material fact or omit to state a material fact required to be stated therein or
necessary to make the statements therein not misleading in light of the
circumstances then existing;

            (vii) if the offering is underwritten and at the request of any
selling Holder, furnish on the date that Restricted Stock is delivered to the
underwriters for sale pursuant to such registration: (1) an opinion dated such
date of counsel representing the Company for the purposes of such registration,
addressed to the underwriters and to such selling Holder, stating that such
registration statement has become effective under the Act and that (A) to the
best knowledge of such counsel, no stop order suspending the effectiveness
thereof has been issued and no proceedings for that purpose have been instituted
or are pending or contemplated under the Act, (B) the registration statement,
the related prospectus and each amendment or supplement thereof comply as to
form in all material respects with the requirements of the Act (except that such
counsel need not express any opinion as to financial statements contained
therein) and (C) to such other effects as reasonably may be requested by counsel
for the underwriters or by such selling Holder or its counsel; and (2) a letter
dated such date from the independent public accountants retained by the Company,
addressed to the underwriters and to such selling Holder, stating that they are
independent public accountants within tile meaning of the Act and that, in the
opinion of such accountants, the financial statements of the Company included in
the registration statement or the prospectus, or any amendment or supplement
thereof, comply as to form in all material respects with the applicable
accounting requirements of the Act, and such letter shall additionally cover
such other financial matters (including information as to the period ending no
more than five (5) business days prior to the date of such letter) with respect
to such registration as such underwriters reasonably may request; and

                                      -9-
<PAGE>

            (viii) make available for inspection by each selling Holder, any
underwriter participating in any distribution pursuant to such registration
statement, and any attorney, accountant or other agent retained by such selling
Holder or underwriter, all financial and other records, pertinent corporate
documents and properties of the Company, and cause the Company's officers,
directors and employees to supply all information reasonably requested by any
such selling Holder, underwriter, attorney, accountant or agent in connection
with such registration statement.

      For purposes of Section 9(c)(i) and 9(c)(ii), the period of distribution
of Restricted Stock in a firm commitment underwritten public offering shall be
deemed to extend until each underwriter has completed the distribution of all
securities purchased by it, and the period of distribution of Restricted Stock
in any other registration shall be deemed to extend until the earlier of the
sale of all Restricted Stock covered thereby and one hundred twenty (120) days
after the effective date thereof.

      In connection with each registration hereunder, the selling Holders will
furnish to the Company in writing such information with respect to themselves
and the proposed distribution by them as shall be reasonably necessary in order
to assure compliance with federal and applicable state securities laws and to
make the registration statement correct, accurate and complete in all material
respects with respect to such selling Holders' participating in the offering;
provided that this requirement shall not be deemed to limit any disclosure
obligation arising out of any selling Holder's relationship to the Company if
one of such Holder's agents or affiliates is an officer, director or control
person of the Company. In addition, in connection with any underwritten
registration, the selling Holders shall, if requested by the Company, execute
such other underwriting related agreements, which are reasonably satisfactory to
them and which shall contain such provisions as may be customary and reasonable
in order to accomplish the registration of the Restricted Stock.

      In connection with each registration pursuant to Section 9(b) covering an
underwritten public offering, the Company and each selling Holder agree to
enter into a written agreement with the managing underwriter in such form and
containing such provisions as are customary in the securities business for such
an arrangement between such underwriter and companies of the Company's size and
investment stature.

      (d)   Expenses. All expenses incurred by the Company in complying with
Section 9(b), including without limitation all registration and filing fees,
printing expenses, fees and disbursements of counsel and independent public
accountants for the Company, fees and expenses (including fees and disbursements
for one counsel of all holders of Company securities to be registered, including
the selling Holders) incurred in connection with complying with state securities
or "blue sky" laws, fees of the National Association of Securities Dealers,
Inc., transfer taxes, fees of transfer agents and registrars, costs of
insurance, but excluding any Selling Expenses, are herein collectively referred
to as "Registration Expenses". All underwriting discounts and selling
commissions applicable to the sale of Restricted Stock are herein collectively
referred to as "Selling Expenses".

      The Company will pay all Registration Expenses in connection with each
registration statement under Section 9(b). All Selling Expenses in connection
with each registration statement under Section 9(b) shall be borne by the
participating sellers of securities (including the selling

                                      -10-
<PAGE>

Holders) in proportion to the number of shares sold by each, or by such
participating sellers other than the Company (except to the extent the Company
shall be a seller) as they may agree.

      (e)   Indemnification and Contribution. (i) In the event of a registration
of any of the Restricted Stock under the Act pursuant to Section 9(b), the
Company will indemnify and hold harmless each selling Holder thereunder, each
underwriter of such Restricted Stock thereunder and each other person, if any,
who controls such selling Holder or underwriter within the meaning of the Act,
against any losses, claims, damages or liabilities, joint or several, to which
such selling Holder, underwriter or controlling person may become subject under
the Act or otherwise, insofar as such losses, claims, damages or liabilities (or
actions in respect thereof) arise out of or are based upon any untrue statement
or alleged untrue statement of any material fact contained in any registration
statement under which such Restricted Stock was registered under the Act
pursuant to Section 9(b), any preliminary prospectus or final prospectus
contained therein, or any amendment or supplement thereof, or arise out of or
are based upon the omission or alleged omission to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading, and will reimburse each such selling Holder, each such underwriter
and each such controlling person for any legal or other expenses reasonably
incurred by them in connection with investigating or defending any such loss,
claim, damage, liability or action; provided that the Company will not be liable
in any such case if and to the extent that any such loss, claim, damage or
liability arises out of or is based upon an untrue statement or alleged untrue
statement or omission or alleged omission so made in conformity with information
furnished by any such selling Holder, any such underwriter or any such
controlling person in writing specifically for use in such registration
statement or prospectus.

            (ii)  In the event of a registration of any of the Restricted Stock
under the Act pursuant to Section 9(b), each selling Holder thereunder,
severally and not jointly, will indemnify and hold harmless the Company, each
person, if any, who controls the Company within the meaning of the Act, each
officer of the Company who signs the registration statement, each director of
the Company, each underwriter and each person who controls any underwriter
within the meaning of the Act, against all losses, claims, damages or
liabilities, joint or several, to which the Company or such officer, director,
underwriter or controlling person may become subject under the Act or
otherwise, insofar as such losses, claims, damages or liabilities (or actions in
respect thereof) arise out of or are based upon any untrue statement or alleged
untrue statement of any material fact contained in the registration statement
under which such Restricted Stock was registered under the Act pursuant to
Section 9(b), any preliminary prospectus or final prospectus contained therein,
or any amendment or supplement thereof, or arise out of or are based upon the
omission or alleged omission to state therein a material fact required to be
stated therein or necessary to make the statements therein not misleading, and
will reimburse the Company and each such officer, director, underwriter and
controlling person for any legal or other expenses reasonably incurred by them
in connection with investigating or defending any such loss, claim, damage,
liability or action; provided that such selling Holder will be liable hereunder
in any such case if and only to the extent that any such loss, claim, damage or
liability arises out of or is based upon an untrue statement or alleged untrue
statement or omission or alleged omission made in reliance upon and in
conformity with information pertaining to such selling Holder, as such,
furnished in writing to the Company by such selling Holder specifically for use
in such registration statement or prospectus or preliminary amendment or

                                      -11-
<PAGE>

supplement thereof; provided further that the liability of each selling Holder
hereunder shall be limited to the net proceeds received by such selling Holder
from the sale of Restricted Stock covered by such registration statement.

            (iii) Promptly after receipt by an indemnified party hereunder of
notice of the commencement of any action, such indemnified party shall, if a
claim in respect thereof is to be made against the indemnifying party hereunder,
notify the indemnifying party in writing thereof, but the omission so to notify
the indemnifying party shall not relieve it from any liability which it may have
to such indemnified party other than under this Section 9(e) and shall only
relieve it from any liability that it may have to such indemnified party under
this Section 9(e) if and to the extent the indemnifying party is prejudiced by
such omission. In case any such action shall be brought against any indemnified
party and it shall notify the indemnifying party of the commencement thereof,
the indemnifying party shall be entitled to participate in and, to the extent it
shall wish, to assume and undertake the defense thereof with counsel
satisfactory to such indemnified party, and, after notice from the indemnifying
party to such indemnified party of its election so to assume and undertake the
defense thereof, the indemnifying party shall not be liable to such indemnified
party under this Section 9(e) for any legal expenses subsequently incurred by
such indemnified party in connection with the defense thereof; provided that if
the defendants in any such action include both the indemnified party and the
indemnifying party and the indemnified party shall have reasonably concluded
that there may be reasonable defenses available to it which are different from
or additional to those available to the indemnifying party or if the interests
of the indemnified party reasonably may be deemed to conflict with the interests
of the indemnifying party, the indemnified party shall have the right to select
a separate counsel and to assume such legal defenses and otherwise to
participate in the defense of such action, with the expenses and fees of such
separate counsel and other expenses related to such participation to be
reimbursed by the indemnifying party as incurred.

            (iv)  In order to provide for just and equitable contribution to
joint liability under the Act in any case in which either (i) any selling
Holder, or any controlling person of any such Holder, makes a claim for
indemnification pursuant to this Section 9(e) but it is judicially determined
(by the entry of a final judgment or decree by a court of competent jurisdiction
and the expiration of time to appeal or the denial of the last right of appeal)
that such indemnification may not be enforced in such case notwithstanding the
fact that this Section 9(e) provides for indemnification in such case, or (ii)
contribution under the Act may be required on the part of any such selling
Holder or any such controlling person in circumstances for which indemnification
is provided under this Section 9(e); then, and in each such case, the Company
and such Holder will contribute to the aggregate losses, claims, damages or
liabilities to which they may be subject (after contribution from others) in
such proportion so that such Holder is responsible for the portion represented
by the percentage that the public offering price of its Restricted Stock offered
by the registration statement bears to the public offering price of all
securities offered by such registration statement, and the Company is
responsible for the remaining portion; provided that, in any such case, (A) no
such Holder will be required to contribute any amount in excess of the net
proceeds received by such Holder from the sale of all such Restricted Stock
offered by it pursuant to such registration statement; and (B) no person or
entity guilty of fraudulent misrepresentation (within the

                                      -12-
<PAGE>

meaning of Section 11(f) of the Act) will be entitled to contribution from any
person or entity who was not guilty of such fraudulent misrepresentation.

      (f)   Changes in Common Stock or Series Preferred. If, and as often as,
there is any change in the Common Stock or the Series Preferred by way of a
stock split, stock dividend, combination or reclassification, or through a
merger, consolidation, reorganization or recapitalization, or by any other
means, appropriate adjustment shall be made in the provisions hereof so that the
rights and privileges granted hereby shall continue with respect to the Common
Stock or the Series Preferred as so changed.

      (g)   Rule 144 Reporting. With a view to making available the benefits of
certain rules and regulations of the Commission that may at any time permit the
sale of the Restricted Stock to the public without registration, at all times
after ninety (90) days after any registration statement covering a public
offering of securities of the Company under the Act shall have become effective,
the Company agrees to:

            (i)   make and keep public information available, as those terms are
understood and defined in Rule 144 under the Act;

            (ii)  use commercially reasonable to file with the Commission in a
timely manner all reports and other documents required of the Company under the
Act and the Exchange Act; and

            (iii) furnish to each Holder forthwith upon request a written
statement by the Company as to its compliance with the reporting requirements of
such Rule 144 and of the Act and the Exchange Act, a copy of the most recent
annual or quarterly report of the Company, and such other reports and documents
so filed by the Company as such holder may reasonably request in availing itself
of any rule or regulation of the Commission allowing such holder to sell any
Restricted Stock without registration.

      (h)   Miscellaneous.

            (i)   All covenants and agreements contained in this Section 9 by or
on behalf of any of the parties hereto shall bind and inure to the benefit of
the respective successors and assigns of the parties hereto, whether so
expressed or not; provided that registration rights conferred herein on the
Holders shall only inure to the benefit of a transferee of this Warrant or any
Series B Preferred or Common stock into which it is exercisable or convertible
if: (1) there is transferred to such transferee (A) at least at 20,000 shares of
Restricted Stock (as adjusted for stock splits, recapitalizations and the like),
or (B) one hundred percent (100%) of the shares of Restricted Stock originally
issuable to the direct or indirect transferor of such transferee, or, in either
case, such portion of this Warrant as relates thereto, and such transferee is
not primarily engaged in any business (other than the Company) that competes in
any material way with the products or services developed, manufactured or sold
by the Company; or (2) such transferee is a partner, shareholder or affiliate of
a party hereto; provided further that such transferee agrees to be bound by the
terms of this Warrant applicable to the holder thereof by executing and
delivering to the Company an instrument of accession hereto, in form and
substance reasonably satisfactory to the Company.

                                      -13-
<PAGE>

            (ii)  The obligations of the Company to register shares of
Restricted Stock under Section 9(b) shall terminate on the earlier of (1) the
tenth anniversary of the Date of Grant or (2) the date that all of such
Restricted Stock held by the holder of this Warrant may be sold under Rule 144
during any ninety (90) day period.

            (iii) If requested in writing by the underwriters for the initial
underwritten public offering of securities of the Company, each Holder shall
agree not to sell publicly any shares of Restricted Stock or any other shares of
Common Stock (other than shares of Restricted Stock or other shares of Common
Stock being registered in such offering), without the consent of such
underwriters, for a period of not more than one hundred eighty (180) days
following the effective date of the registration statement relating to such
offering; provided that all other persons entitled to registration rights with
respect to shares of Common Stock, all other persons selling shares of Common
Stock in such offering, all persons holding in excess of one percent (1%) of the
capital stock of the Company on a fully diluted basis and all executive officers
and directors of the Company shall also have agreed not to sell publicly their
Common Stock under the circumstances and pursuant to the terms set forth in this
Section 9(h)(iii).

            (iv)  Notwithstanding the provisions of Section 9(c)(i), the
Company's obligation to file a registration statement pursuant to Section 9(b),
or cause such registration statement to become and remain effective, may be
suspended if there exists at the time material non-public information relating
to the Company which, in the reasonable opinion of the Company, should not be
disclosed.

            (v)   The Company shall not grant to any third party lender (other
than a lender who is (or who would become if such lender converted all
convertible securities acquired by such lender at the time of the making of a
loan to the Company) primarily an equity investor in the Company) any
registration rights more favorable than those contained herein, so long as any
of the registration rights hereunder remain in effect, unless such more
favorable rights are simultaneously granted to the holder hereof.

      10.   Additional Rights.

      10.1  Acquisition Transactions. The Company shall provide the holder of
this Warrant with at least twenty (20) days' written notice prior to closing
thereof of the terms and conditions of any of the following transactions (to the
extent the Company has notice thereof): (i) the sale, lease, exchange,
conveyance or other disposition of all or substantially all of the Company's
property or business; or (ii) its merger into or consolidation with any other
corporation (other than a wholly-owned subsidiary of the Company), or any
transaction (including a merger or other reorganization) or series of related
transactions, of which the Company has knowledge, in which more than fifty
percent (50%) of the voting power of the Company is disposed of. The Company's
obligations to the holder under this Section 10.1 shall be contingent upon such
holder's agreement, and such holder hereby agrees, to keep confidential all
information received by or disclosed to such holder by the Company in the
fulfillment of the Company's obligations under this Section 10.1, to refrain
from the use (other than for internal evaluation purposes) or disclosure of such
information, and to refrain from trading in the Company's securities while in
possession of such information if such trading would contravene any provision of
the Act or the Securities Exchange Act of 1934, as amended.

                                      -14-
<PAGE>

      10.2  Right to Convert Warrant into Stock: Net Issuance.

            (a)   Right to Convert. Without limiting the rights of the holder
under the terms of this Warrant, in lieu of the full or partial exercise of the
payment method of exercise described in Section 2(a), the holder shall have the
right to convert this Warrant or any portion thereof (the "Conversion Right")
into shares of Series Preferred as provided in this Section 10.2 at any time or
from time to time during the term of this Warrant. Upon exercise of the
Conversion Right with respect to a particular number of shares subject to this
Warrant (the "Converted Warrant Shares"), the Company shall deliver to the
holder (without payment by the holder of any exercise price or any cash or other
consideration) that number of shares of fully paid and nonassessable Series
Preferred as is determined according to the following formula:

          B-A
      X = ---
           Y

      Where: X =  the number of shares of Series Preferred that shall be issued
                  to holder

             Y =  the fair market value of one share of Series Preferred

             A =  the aggregate Warrant Price of the specified number of
                  Converted Warrant Shares immediately prior to the exercise of
                  the Conversion Right (i. e., the number of Converted Warrant
                  Shares multiplied by the Warrant Price)

             B =  the aggregate fair market value of the specified number of
                  Converted Warrant Shares (i.e., the number of Converted
                  Warrant Shares multiplied by the fair market value of one
                  Converted Warrant Share)

      No fractional shares shall be issuable upon exercise of the Conversion
Right, and, if the number of shares to be issued determined in accordance with
the foregoing formula is other than a whole number, the Company shall pay to the
holder an amount in cash equal to the fair market value of the resulting
fractional share on the Conversion Date (as hereinafter defined). For purposes
of Section 10 of this Warrant, shares issued pursuant to the Conversion Right
shall be treated as if they were issued upon the exercise of this Warrant.

            (b)   Method of Exercise. The Conversion Right may be exercised by
the holder by the surrender of this Warrant at the principal office of the
Company together with a written statement (which may be in the form of Exhibit
A-1 or Exhibit A-2 hereto) specifying that the holder thereby intends to
exercise the Conversion Right and indicating the number of shares subject to
this Warrant which are being surrendered (referred to in Section 10.2(a) hereof
as the Converted Warrant Shares) in exercise of the Conversion Right. Such
conversion shall be effective upon receipt by the Company of this Warrant
together with the aforesaid written statement, or on such later date as is
specified therein (the "Conversion Date"), and, at the election of the holder
hereof, may be made contingent upon the closing of the sale of the Company's
Common Stock to the public in a public offering pursuant to a Registration
Statement under the Act (a "Public Offering"). Certificates for the shares
issuable upon exercise of the Conversion Right and, if applicable, a new warrant

                                      -15-
<PAGE>

evidencing the balance of the shares remaining subject to this Warrant, shall be
issued as of the Conversion Date and shall be delivered to the holder within
thirty (30) days following the Conversion Date.

            (c)   Determination of Fair Market Value. For purposes of this
Section 10.2, "fair market value" of a share of Series Preferred (or Common
Stock if the Series Preferred has been automatically converted into Common
Stock) as of a particular date (the "Determination Date") shall mean:

                  (i)   If the Conversion Right is exercised in connection with
and contingent upon a Public Offering, and if the Company's Registration
Statement relating to such Public Offering ("Registration Statement") has been
declared effective by the Securities and Exchange Commission, then the initial
"Price to Public" specified in the final prospectus with respect to such
offering.

                  (ii)  If the Conversion Right is not exercised in connection
with and contingent upon a Public Offering, then as follows:

            (A)   If traded on a securities exchange, the fair market value of
the Common Stock shall be deemed to be the average of the closing prices of the
Common Stock on such exchange over the five trading days immediately prior to
the Determination Date, and the fair market value of the Series Preferred shall
be deemed to be such fair market value of the Common Stock multiplied by the
number of shares of Common Stock into which each share of Series Preferred is
then convertible;

            (B)   If traded on the Nasdaq Stock Market or other over-the-counter
system, the fair market value of the Common Stock shall be deemed to be the
average of the closing bid prices of the Common Stock over the five trading days
immediately prior to the Determination Date, and the fair market value of the
Series Preferred shall be deemed to be such fair market value of the Common
Stock multiplied by the number of shares of Common Stock into which each share
of Series Preferred is then convertible; and

            (C)   If there is no public market for the Common Stock, then fair
market value shall be determined in good faith by the Company's Board of
Directors.

In making a determination under clauses (A) or (B) above, if on the
Determination Date, five (5) trading days had not passed since the closing of
the Company's initial Public Offering, then the fair market value of the Common
Stock shall be the average closing prices or closing bid prices, as applicable,
for the shorter period beginning on and including the date of such initial
Public Offering and ending on the trading day prior to the Determination Date
(or if such period includes only one trading day the closing price or closing
bid price, as applicable, for such trading day). If closing prices or closing
bid prices are no longer reported by a securities exchange or other trading
system, the closing price or closing bid price shall be that which is reported
by such securities exchange or other trading system at 4:00 p.m. New York City
time on the applicable trading day.

      10.3  Exercise Prior to Expiration. To the extent this Warrant is not
previously exercised as to all of the Shares subject hereto, and if the fair
market value of one share of the Series Preferred

                                      -16-
<PAGE>

is greater than the Warrant Price then in effect, this Warrant shall be deemed
automatically exercised pursuant to Section 10.2 above (even if not surrendered)
immediately before its expiration. For purposes of such automatic exercise, the
fair market value of one share of the Series Preferred upon such expiration
shall be determined pursuant to Section 10.2(c). To the extent this Warrant or
any portion thereof is deemed automatically exercised pursuant to this Section
10.3, the Company agrees to promptly notify the holder hereof of the number of
Shares, if any, the holder hereof is to receive by reason of such automatic
exercise.

      11.  Representations and Warranties. The Company represents and warrants
to the holder of this Warrant as follows:

            (a)   This Warrant has been duly authorized and executed by the
Company and is a valid and binding obligation of the Company enforceable in
accordance with its terms, subject to laws of general application relating to
bankruptcy, insolvency and the relief of debtors and the rules of law or
principles at equity governing specific performance, injunctive relief and other
equitable remedies.

            (b)   The Shares have been duly authorized and reserved for issuance
by the Company and, when issued in accordance with the terms hereof, will be
validly issued, fully paid and nonassessable and free from preemptive rights.

            (c)   The rights, preferences, privileges and restrictions granted
to or imposed upon the Series Preferred and the holders thereof are as set forth
in the Charter, and on the Date of Grant, each share of the Series Preferred
represented by this Warrant is convertible into one share of Common Stock.

            (d)   The shares of Common Stock issuable upon conversion of the
Shares have been duly authorized and reserved for issuance by the Company and,
when issued in accordance with the terms of the Charter will be validly issued,
fully paid and nonassessable.

            (e)   The execution and delivery of this Warrant are not, and the
issuance of the Shares upon exercise of this Warrant in accordance with the
terms hereof will not be, inconsistent with the Company's Charter or by-laws, do
not and will not contravene any law, governmental rule or regulation, judgment
or order applicable to the Company, and do not and will not conflict with or
contravene any provision of, or constitute a default under, any indenture,
mortgage, material contract or other material instrument of which the Company is
a party or by which it is bound or require the consent or approval of, the
giving of notice to, the registration or filing with or the taking of any action
in respect of or by, any Federal, state or local government authority or agency
or other person, except for the filing of notices pursuant to federal and state
securities laws, which filings will be effected by the time required thereby.

            (f)   There are no actions, suits, audits, investigations or
proceedings pending or, to the knowledge of the Company, threatened against the
Company in any court or before any governmental commission, board or authority
which, if adversely determined, could have a material adverse effect on the
ability of the Company to perform its obligations under this Warrant.

                                      -17-
<PAGE>

            (g)   The number of shares of Common Stock of the Company
outstanding on the date hereof, on a fully diluted basis (assuming the
conversion of all outstanding convertible securities and the exercise of all
outstanding options and warrants), does not exceed 80,786,000 shares.

      12.   Modification and Waiver. This Warrant and any provision hereof may
be changed, waived, discharged or terminated only by an instrument in writing
signed by the party against which enforcement of the same is sought.

      13.   Notices. Any notice, request, communication or other document
required or permitted to be given or delivered to the holder hereof or the
Company shall he delivered, or shall be sent by certified or registered mail,
postage prepaid, to each such holder at its address as shown on the books of the
Company or to the Company at the address indicated therefor on the signature
page of this Warrant.

      14.   Binding Effect on Successors. This Warrant shall be binding upon any
corporation succeeding the Company by merger, consolidation or acquisition of
all or substantially all of the Company's assets, and all of the obligations of
the Company relating to the Series Preferred issuable upon the exercise or
conversion of this Warrant shall survive the exercise, conversion and
termination of this Warrant and all of the covenants and agreements of the
Company shall inure to the benefit of the successors and assigns of the holder
hereof.

      15.   Lost Warrants or Stock Certificates. The Company covenants to the
holder hereof that, upon receipt of evidence reasonably satisfactory to the
Company of the loss, theft, destruction or mutilation of this Warrant or any
stock certificate and, in the case of any such loss, theft or destruction, upon
receipt of an indemnity reasonably satisfactory to the Company, or in the case
of any such mutilation upon surrender and cancellation of such Warrant or stock
certificate, the Company will make and deliver a new Warrant or stock
certificate, of like tenor, in lieu of the lost, stolen, destroyed or mutilated
Warrant or stock certificate.

      16.   Descriptive Headings. The descriptive headings of the various
Sections of this Warrant are inserted for convenience only and do not constitute
a part of this Warrant. The language in this Warrant shall be construed as to
its fair meaning without regard to which party drafted this Warrant.

      17.   Governing Law. This Warrant shall be construed and enforced in
accordance with, and the rights of the parties shall be governed by, the laws of
the Commonwealth of Massachusetts.

      18.   Survival of Representations, Warranties and Agreements. All
representations and warranties of the Company and the holder hereof contained
herein shall survive the Date of Grant, the exercise or conversion of this
Warrant (or any part hereof) or the termination or expiration of rights
hereunder. All agreements of the Company and the holder hereof contained herein
shall survive indefinitely until, by their respective terms, they are no longer
operative.

      19.   Remedies. In case any one or more of the covenants and agreements
contained in this Warrant shall have been breached, the holders hereof (in the
case of a breach by the Company), or

                                      -18-
<PAGE>

the Company (in the case of a breach by a holder), may proceed to protect and
enforce their or its rights either by suit in equity and/or by action at law,
including, but not limited to, an action for damages as a result of any such
breach and/or an action for specific performance of any such covenant or
agreement contained in this Warrant.

      20.   No impairment of Rights. The Company will not, by amendment of its
Charter or through any other means, avoid or seek to avoid the observance or
performance of any of the terms of this Warrant, but will at all times in good
faith assist in the carrying out of all such terms and in the taking of all such
action as may be necessary or appropriate in order to protect the rights of the
holder of this Warrant against impairment.

      21.   Severability. The invalidity or unenforceability of any provision of
this Warrant in any jurisdiction shall not affect the validity or enforceability
of such provision in any other jurisdiction, or affect any other provision of
this Warrant, which shall remain in full force and effect.

      22.   Recovery of Litigation Costs. If any legal action or other
proceeding is brought for the enforcement of this Warrant, or because of an
alleged dispute, breach, default, or misrepresentation in connection with any of
the provisions of this Warrant, the successful or prevailing party or parties
shall be entitled to recover reasonable attorneys' fees and other costs incurred
in that action or proceeding, in addition to any other relief to which it or
they may be entitled.

      23.   Entire Agreement; Modification. This Warrant constitutes the entire
agreement between the parties pertaining to the subject matter contained in it
and supersedes all prior and contemporaneous agreements, representations, and
undertakings of the parties, whether oral or written, with respect to such
subject matter.

                  [Remainder of page intentionally left blank.]

                                      -19-
<PAGE>

      The Company has caused this Warrant to be duly executed and delivered as
of the Date of Grant specified above.

                                                 EGENERA, INC.

                                                 BY /s/ Thomas F. Sheehan
                                                   -----------------------------
                                                 Title CFO

                                                 Address: 165 Forest Street
                                                          Marlboro, MA 01752

                                                 GATX VENTURES, INC.

                                                 By /s/ Robert D. Pomeroy, Jr.
                                                   -----------------------------
                                                 Title Senior Vice President

                                                 Address: 16 Muson Road
                                                          Farmington, CT 06032

                                      -20-

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