Date: Mon, 07 Dec 1998 22:49:59 +0100 From: Gary Jennejohn <garyj@peedub.muc.de> To: "Ron G. Minnich" <rminnich@Sarnoff.COM> Cc: hackers@FreeBSD.ORG Subject: Re: write combining memory on pci Message-ID: <199812072149.WAA03166@peedub.muc.de> In-Reply-To: Your message of "Mon, 07 Dec 1998 16:14:08 EST." <Pine.SUN.3.91.981207161159.9378E-100000@terra>
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"Ron G. Minnich" writes: > >On Mon, 7 Dec 1998, Karl Pielorz wrote: >> Both my P-Pro systems have this option, and AFAIK it worked as above (i.e. >> 'all on' or 'all off')... Win NT survives with it on, until I try to use the >> sound card, and FreeBSD, Linux & Win'95 all die within seconds with it on > >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 :-) > >> Which is a bit of a pitty, as I also seem to remember reading it gives a hug >e >> performance win on writes ;-) - Maybe there is such a thing as 'too fast'... > >something on order of at least 2x. It would be nice to have ... > an example of this is the fastvid lkm originally written by John Dyson and modified by Lars Koeller. It's available on Lars' home page (which you can find by looking at the README in hte xperfmon++ port, I believe). This seems to be a general-purpose write combine thingy, since it applies to a range of memory. Maybe you can modify it to meet your requirements. I use this on a PPro system (and I've tried it on a P-II, but the system became unstable - which may not heve been due to fastvid), so it may also work for you. --- Gary Jennejohn Home - garyj@muc.de Work - garyj@fkr.dec.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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