Date: Sun, 17 Feb 2002 15:36:56 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Michael Smith <msmith@FreeBSD.ORG> Cc: Michael Smith <msmith@FreeBSD.ORG>, Poul-Henning Kamp <phk@critter.freebsd.dk>, Bruce Evans <bde@zeta.org.au>, freebsd-current@FreeBSD.ORG Subject: Re: ACPI timer is screwed... (was Re: 'microuptime() went backwards ...' using ACPI timer. Shouldn't that be impossible? ) Message-ID: <200202172336.g1HNaup07553@apollo.backplane.com> References: <200202172327.g1HNRuA01838@mass.dis.org>
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:Sounds like we need to smack whoever made your chipset as well. Intel :learned their lesson (finally) with later revisions of the PIIX4. I'm :guessing you're running this against a ServerWorks system. atapci0: <ServerWorks ROSB4 ATA33 controller> port 0x8b0-0x8bf at device 15.1 on pci0 Uh huh. It might be possible to detect the situation during init-time by explicitly looking for a reverse indexed time in a tight loop of maybe a thousand reads, but that would still leave us with a statistical chance of not guessing right. :Interesting. This would be reasonably robust in the ripple-counter case :we have to deal with on the old PIIX4. Have you tried implementing the :above yet, or measuring how much it costs? : :At any rate, please let me know for sure whether you're running on a :ServerWorks board, and I'll see if I can't find a Big Stick to hit them :with. : :Thanks, :Mike I haven't measured the cost (extra loops) but I expect it would stabilize in no more then one additional loop, which would be three counter reads total or roughly the same as your originaln _safe code in the worst case. I think we could default to the _safe version and then explicitly change it to use the fast version if we see specific chipsets which we know to be good. -Matt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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