Dec 04
Erratum Plagues Quad-Core Opterons, Phenoms
Dec 04, ‘07 — Slashdot reports on a story by “The Tech Report” on possible chip problems with AMD’s quad-core Opteron, Phenom processors.
“Errata are not uncommon with new processors, but a problem with the TLB logic in AMD’s quad-core Opteron and Phenom processors appears to be quite serious. The erratum is so severe that AMD has issued a ’stop ship’ order on all quad-core Opterons.
AMD has also blamed this bug for the delay of the 2.4GHz Phenom, despite the fact that the erratum is unrelated to clock speed. A BIOS-based workaround for the issue has been made available to motherboard makers, but it apparently carries a 10-20% performance penalty.
What’s more disturbing is that AMD knew of the erratum and the potential performance hit associated with fixing it before it launched the Phenom processor. Hardware provided to the press for reviews did not include the fix, conveniently overstating Phenom performance.”
Excerpts from The Tech Report:
“The erratum is a chip-level issue involving the TLB logic for the L3 cache that can cause system hangs in specific circumstances. AMD has a fix for the problem in the works, but it degrades performance.
In order to better understand this problem, TR spoke with Michael Saucier, Desktop Product Marketing Manager at AMD. Saucier confirmed that the TLB erratum can cause the system to hang when the chip is experiencing high utilization.
Apparently contradicting prior AMD statements on the matter, Saucier flatly denied any relationship between the TLB erratum and chip clock frequencies. He also said there’s no relationship between clock speeds and the performance degradation caused by the BIOS-based fix for the erratum.
we’ve already discovered that our Phenom review overstates the performance of the 2.3GHz Phenom. We tested at a 2.3GHz core clock with a 2.0GHz north bridge clock, because AMD told us those speeds were representative of the Phenom 9600. Our production samples of the Phenom 9500 and 9600, however, have north bridge clocks of 1.8GHz.”
More at The Tech Report.