From owner-freebsd-hackers Mon Dec 7 13:41:11 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id NAA19693 for freebsd-hackers-outgoing; Mon, 7 Dec 1998 13:41:11 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from caladan.tdx.co.uk (caladan.tdx.co.uk [195.188.177.4]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id NAA19676 for ; Mon, 7 Dec 1998 13:41:05 -0800 (PST) (envelope-from kpielorz@tdx.co.uk) Received: from tdx.co.uk (lorca-tx.tdx.co.uk [195.188.177.242]) by caladan.tdx.co.uk (8.9.1a/8.9.1) with ESMTP id VAA60305; Mon, 7 Dec 1998 21:40:57 GMT Message-ID: <366C4B68.DB46F3CF@tdx.co.uk> Date: Mon, 07 Dec 1998 21:40:56 +0000 From: Karl Pielorz Organization: TDX - The Digital eXchange X-Mailer: Mozilla 4.5 [en] (WinNT; I) X-Accept-Language: en MIME-Version: 1.0 To: "Ron G. Minnich" CC: hackers@FreeBSD.ORG Subject: Re: write combining memory on pci References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG "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