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Gentoo.org: AMD's official position: this is not a CPU bug

Jan 24, 2002, 16:45 (16 Talkback[s])

[ Thanks to Leo for this link. ]

"Yesterday, Rik van Riel, William Lee Irwin and myself were able to discuss this issue of Athlon/AGP instability with AMD. This converation was very enlightening, to say the least.

Let's start with some facts. The issue that is being discussed here is not related to the so-called "INVPLG bug". So, what is the issue, and who's at fault? Yesterday, AMD offered us an explanation of what may be happening to cause AGP instability on Linux systems. This explanation appears to be the exact scenario that bit Windows 2000 in September 2000. AMD characterizes this issue as a cache coherency problem resulting from how other components on the motherboard (the GART in particular) interact with a particular performance-enhancing feature of the Athlon Processor called speculative writes. The GART and the CPU have two different views of memory -- the GART's view does not "see" the contents of the Athlon's internal caches, and herein lies the problem. In certain situations the CPU and the GART can step on each other's toes, resulting in memory corruption. For more information, see my Linux kernel mailing list post that contains an explanation of this particular problem in AMD's own words."

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