Date: Fri, 6 Nov 1998 09:41:12 -0500 (EST) From: "Ron G. Minnich" <rminnich@Sarnoff.COM> To: lcremean@tidalwave.net Cc: hackers@FreeBSD.ORG Subject: Re: Coprocessor board--which I/O method should I use? Message-ID: <Pine.SUN.3.91.981106093938.28856A-100000@terra> In-Reply-To: <19981106083018.B2926@tidalwave.net>
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On Fri, 6 Nov 1998, Lee Cremeans wrote: > The chip itself can handle 27 MBytes/s in single DES, 10 Mbytes/s in triple > DES. THere's a data sheet for it if you want to see it; go look at > www.hifn.com, it's the 7751. Right so what I'm saying is this: PII and other Intel-based motherboards can only do PCI reads at 7 Mbytes/second. Intel bridges don't support burst mode reads from the processor to PCI, even in cacheable space. So, if you want to get that bandwidth from the board to main memory you're going to have to have the board do PCI writes in DMA mode. This sort of thing slightly complicates user-mode access. ron To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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