<PAGE>
                                  EXHIBIT 10.9

                       AMENDMENT TO STOCK PLEDGE AGREEMENT

      This Amendment to Stock Pledge Agreement (this "Amendment") is made as of
May 19, 2000 by and among Sebring Systems, Inc., a Delaware corporation (the
"Company") and wholly-owned subsidiary of PLX Technology, Inc., a Delaware
corporation ("PLX"), and Jack Regula (the "Pledgor").

RECITALS

      WHEREAS, the Company (f/k/a Sebring Systems, Inc., a New York corporation)
and Pledgor are parties to that certain Stock Pledge Agreement dated June 18,
1997 (the "Agreement");

      WHEREAS, in connection with the acquisition of the Company by PLX on the
date hereof, all outstanding shares of stock of the Company were converted into
shares of Common Stock of PLX (the "Transaction");

      WHEREAS, upon the closing of the Transaction, Pledgor's Pledged Shares
were converted into 27,155 shares of Common Stock of PLX (the "Replacement
Shares");

      WHEREAS, upon the closing of the Transaction, the Company became a
wholly-owned subsidiary of PLX;

      WHEREAS, the Company and Pledgor now desire to amend the Agreement to
allow PLX to act as the escrow agent for the Pledged Shares and confirm that the
Replacement Shares shall replace the Pledged Shares and shall be subject to the
terms and conditions of the Agreement;

      NOW THEREFORE, in consideration of the mutual agreements and covenants
hereinafter set forth and for other valuable consideration, including the
Company's consent to the sale in the Transaction of all shares of Common Stock
previously held by Pledgor, the parties hereby agree as follows:

AGREEMENT

      1. GRANT OF SECURITY INTEREST IN REPLACEMENT SHARES. The Replacement
Shares shall replace the shares of Common Stock of the Company previously
pledged and shall become subject to the terms and conditions set forth in the
Agreement, and all references in the Agreement to "Pledged Shares" shall refer
to the Replacement Shares. Pledgor hereby grants the Company a security interest
in, and assigns, transfers to and pledges with the Company, the Replacement
Shares.

      References to "the Company's Common Stock" or "Common Stock" in Section
9(ii), (iv) and (v) shall be deemed to refer to the common stock of PLX
Technology, Inc.

      2. ESCROW AGENT. PLX Technology, Inc. shall replace Brobeck, Phleger &
Harrison LLP as escrow agent, and all references to Brobeck, Phleger & Harrison
are hereby amended to refer to PLX Technology, Inc.

      3. MISCELLANEOUS.

         (A) COUNTERPARTS. This Amendment may be executed in any number of
counterparts, each of which shall be deemed an original, but all such
counterparts together shall constitute but one and the same instrument.


         (B) AGREEMENT AFFIRMED. Except as amended hereby, the Agreement and all
of the rights, duties, powers, obligations and interests of the parties
thereunder shall remain in full force and effect.


         (C) ENTIRE AGREEMENT. This Amendment and the Agreement and the
documents contemplated therein, embody the entire agreement and understanding
between the parties with regard to the subject matter hereof and thereof, and
supersede all prior negotiations, agreements and understandings, oral or
written.
<PAGE>

         (D) CAPITALIZATION. Capitalized terms not otherwise defined in this
Amendment shall have the same meaning as set forth in the Agreement.


         (E) COUNTERPARTS. This Amendment may be executed in any number of
counterparts, each of which shall be deemed an original, but all of which shall
constitute one and the same instrument.


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

                                                COMPANY:

                                                Sebring Systems, Inc.,
                                                a Delaware corporation

                                                By:   /s/    Michael J. Salameh
                                                      --------------------------
                                                      Michael J. Salameh,
                                                      President



                                                PLEDGOR:

                                                By:   /s/    Jack Regula
                                                      --------------------------
                                                      Jack Regula