Date: Sat, 31 Oct 1998 16:08:09 +0200 (EET) From: Narvi <narvi@haldjas.folklore.ee> To: Mike Smith <mike@smith.net.au> Cc: Tom <tom@uniserve.com>, "Milliken, Scott" <MillikS@salestech.com>, "'stable@freebsd.org'" <stable@FreeBSD.ORG> Subject: Re: RAID support in FBSD? Message-ID: <Pine.BSF.3.96.981031155813.13946I-100000@haldjas.folklore.ee> In-Reply-To: <199810301754.JAA00882@dingo.cdrom.com>
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On Fri, 30 Oct 1998, Mike Smith wrote: > > This is wrong. Max sustained bandwidth for 33Mhz 32bit PCI bus is 80MB/s. > > 132MB/s is the theoretical peak bandwidth on an infinite burst transfer. > > For higher bandwidth, you need either wider (64 bit) or faster (66Mhz) PCI > > bus. > > You're presuming on the latency timer here, right? I don't recall > there being a cap on the burst length. In the spec, probably yes. But obviously there is a cap on the burst length. The cap is due to the reason that PCI is not AFAIK full-duplex. Once the device has transmitted all data you asked for, it is going to have to pause until you ask for more. FreeBSD does transfers in amounts of max. max_phys_io, right? And ordinary machines have just one PCI<->host bus on which several more things are going on (somebody moves the mouse, a network packet arrives, something is logged to the screen, etc.). > -- > \\ Sometimes you're ahead, \\ Mike Smith > \\ sometimes you're behind. \\ mike@smith.net.au > \\ The race is long, and in the \\ msmith@freebsd.org > \\ end it's only with yourself. \\ msmith@cdrom.com > > Sander There is no love, no good, no happiness and no future - all these are just illusions. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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