said an internal investigation has found discrepancies in past stock option grants.

The San Jose, Calif., chipmaker, which has recently been rocked by a

contentious management shake-up, said after the bell Monday that it expects to restate financial results for the past three years.

The restatements will decrease net income or increase net loss during the period, but Atmel said it did not yet know the exact amount of the restatements, as the investigation is ongoing.

Atmel announced the investigation in late July, putting it in the same boat as more than 100 other companies under scrutiny because of the practice of backdating stock options.

A special audit committee within Atmel, with the assistance of independent legal and forensic accounting expects has reached a preliminary conclusion that "the actual measurement dates for certain stock options differed from the recorded measurement dates for such stock options," the company said in a statement Monday.

As a result, Atmel said that financial reports for the three fiscal years up to 2005, along with the first-quarter report for fiscal 2006, should no longer be relied upon. The restatement will also affect prior periods, though Atmel said those restatements will be reflected in the opening balances as of January31, 2003.

Atmel said it has not yet determined the tax consequences that may result from the findings and has not yet completed an analysis of its internal control over financial reporting.

Shares of Atmel slipped 1.5%, or 8 cents, to $5.44 in extended trading.