Date: Mon, 07 Dec 1998 21:40:56 +0000 From: Karl Pielorz <kpielorz@tdx.co.uk> To: "Ron G. Minnich" <rminnich@Sarnoff.COM> Cc: hackers@FreeBSD.ORG Subject: Re: write combining memory on pci Message-ID: <366C4B68.DB46F3CF@tdx.co.uk> References: <Pine.SUN.3.91.981207161159.9378E-100000@terra>
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"Ron G. Minnich" wrote: > Hmm, that is bad news. I have some cards from a company that only run fast > with write combining turned ON. However, if they crash the OS with it on, > it might not be such a good deal. > > Guess I'll have to use the cards as a master, not a target for PIO > writes. As ever, the rule with PCI: don't get the CPU involved in data > transfer :-) Remember - this was with 'indiscriminate' USWC, you may be able to get away with it if you can enable it for certain regions only... Maybe a trip to the Intel website, or a look through the fastvid code (which will turn on Write Combining + other bits for only certain areas might help)... > something on order of at least 2x. It would be nice to have ... Yeah, I also read it does the equivalent of 'fire and forget' for memory, i.e. you can have overlapping multiple writes arriving out of order... OK, for video - who cares :) ... But for other large memory regions? - Could be fun ;-) -Kp To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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