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EXHIBIT 5

# CERTIFICATION OF CHIEF
EXECUTIVE OFFICER 
PURSUANT TO SECTION 302 OF
THE SARBANES-OXLEY ACT OF 2002

I, David Orton, principal executive
officer of ATI Technologies Inc. (the issuer), certify that:

|1. |  | I
have reviewed this annual report on Form 40-F of the issuer;
|-- |  | --------------------------------------------------------------

|2. |  | Based
on my knowledge, this report does not contain any untrue statement of a
material fact or omit to state a material fact necessary to make the
statements made, in light of the circumstances under which such statements
were made, not misleading with respect to the period covered by this
report;
|-- |  | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

|3. |  | Based
on my knowledge, the financial statements, and other financial information
included in this report, fairly present in all material respects the
financial condition, results of operations and cash flows of the issuer as
of, and for, the periods presented in this report;
|-- |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

|4. |  | The
issuers other certifying officer and I are responsible for
establishing and maintaining disclosure controls and procedures (as
defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the issuer and
have:
|-- |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (a) |  | Designed
such disclosure controls and procedures, or caused such disclosure
controls and procedures to be designed under our supervision, to ensure
that material information relating to the issuer, including its
consolidated subsidiaries, is made known to us by others within those
entities, particularly during the period in which this report is being
prepared;
| | --- |  | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (b) |  | Evaluated
the effectiveness of the issuers disclosure controls and procedures
and presented in this report our conclusions about the effectiveness of
the disclosure controls and procedures, as of the end of the period covered
by this report based on such evaluation; and
| | --- |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (c) |  | Disclosed
in this report any change in the issuers internal control over
financial reporting that occurred during the period covered by the annual
report that has materially affected, or is reasonably likely to materially
affect, the issuers internal control over financial reporting; and
| | --- |  | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

|5. |  | The
issuers other certifying officer and I have disclosed, based on our
most recent evaluation of internal control over financial reporting, to
the issuers auditors and the audit committee of the issuers
board of directors (or persons performing the equivalent functions):
|-- |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (a) |  | All
significant deficiencies and material weaknesses in the design or operation
of internal control over financial reporting which are reasonably likely
to adversely affect the issuers ability to record, process,
summarize and report financial information; and
| | --- |  | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (b) |  | Any
fraud, whether or not material, that involves management or other employees
who have a significant role in the issuers internal control over
financial reporting.
| | --- |  | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------

|Date: January 14, 2005 | By: //David Orton//                  
|---------------------- | -------------------------------------
|                       |                                      
|                       | David Orton                          
|                       | President and Chief Executive Officer