THE most advanced microprocessors produced by Intel, which has a plant in Leixlip, Co Kildare, are not as fast as the company had previously claimed.

A fault in software used to determine the speed of the chips produced false results which overstated the performance of some of Intel's latest chips by about 10 per cent, the company has said.

The error occured in the software rather than the chip itself, however, it is still embarrassing for Intel as it revives memories of the floating decimal point fault in the early versions of the Pentium chip.

"We are embarrassed and truly sorry for this oversight," said Mr Fred Pollack, director of Intel's measurement, chip architecture and planning group. US investors seemed unperturbed by the announcement, which was made late on Friday, as Intel stock opened slightly higher in New York yesterday at $58 1/4. Intel's admission and apology to customers are in stark contrast to its much-criticised reaction to the discovery of the Pentium flaw in 1994.

Intel initially played down the importance of the fault, but IBM stopped shipments of Pentium PCs with the flaw and other vendors offered to replace chips. Intel subsequently changed its stance and said it would replace all flawed Pentium chips. The replacements cost Intel $475 million (£298 million).

Meanwhile, Intel has signed a new five-year cross-licensing agreement with Advanced Micro Devices on certain copyrights and patents.