Date: Thu, 22 Aug 2002 23:31:55 -0700 From: David Schultz <dschultz@uclink.berkeley.edu> To: Terry Lambert <tlambert2@mindspring.com> Cc: Will Andrews <will@csociety.org>, Peter Wemm <peter@wemm.org>, current@FreeBSD.ORG Subject: Re: Memory corruption in -CURRENT [was Re: Plea to committers to only commit to HEAD if you run -current {from developers@FreeBSD.org}] Message-ID: <20020823063155.GA215@HAL9000.homeunix.com> In-Reply-To: <3D65C8B2.EF3EB14@mindspring.com> References: <20020822233846.GJ90596@procyon.firepipe.net> <20020823002846.BBF082A7D6@canning.wemm.org> <20020823004257.GM90596@procyon.firepipe.net> <3D6587ED.F602F06@mindspring.com> <20020823044659.GA2687@HAL9000.homeunix.com> <3D65C8B2.EF3EB14@mindspring.com>
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Thus spake Terry Lambert <tlambert2@mindspring.com>: > David Schultz wrote: > > Thus spake Terry Lambert <tlambert2@mindspring.com>: > > > DISABLE_PSE is a 1:6 probability; DISABLE_PG_G is a 1:100 (both > > > estimates, but on that order), so mixing and matching them will > > > not usually give any additional information. Martin got "lucky" > > > with his machine... it seems to require both. > > > > > > The problem is a hardware bug in most Pentium on up processors, > > > which gets worse in newer CPUs (P4, AMD) as they try to optimize > > > certain things. It's like writing ANSI C without "volatile". > > > > It sounds like you're describing a cache coherence problem. Could > > you elaborate or point me to a reference on this? Thanks. > > There is no reference on this. It is an undocumented hardware bug. Err...so you know there's a long-standing random bug that it has to do with 4 MB pages, but nobody has bothered to characterize it after all these years? This sounds much like the problem Linux had with 4 MB pages and AGP GART on Athlons, where the hardware designers maintained that it was a `feature', not a bug, and that the software people were relying on undocumented behavior. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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