Date: Mon, 8 May 1995 13:51:50 -0700 (PDT) From: Tom Samplonius <tom@haven.uniserve.com> To: "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com> Cc: hackers@FreeBSD.org Subject: Re: Is a 486 fast enough for SCSI? Message-ID: <Pine.BSF.3.91.950508134454.4218A-100000@haven.uniserve.com> In-Reply-To: <199505081929.MAA01292@gndrsh.aac.dev.com>
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On Mon, 8 May 1995, Rodney W. Grimes wrote: > It is not the CPU, but you failed to mention which version of > FreeBSD and particularly the ahc driver you are running. I suspect > that the driver may be detuned for compatibility reasons, but Justin > is the one who would know best on that. I'm running a current kernel. I've heard that tagged command queueing is disabled be default. > You also failed to mention the model of the drives, a parameters like > RPM that greatly effect the raw data rate of the drive (if you have > the media transfer rate number that is the best one to use, it is > usually a range of values due to ZBR recording. The higher number is > what you get for the outer cyclinders, the lower number for the inner > cylinders). Digital DSP3210S. Media transfer rate is 2.5 - 5.5. Drive performance doesn't really explain why performance is halved when two drives are in use. Since PCI can handle up to a 130 MB/s, and FAST SCSI can do 10MB/s, two drives should be able to both run at 2MB/s simultaneously. > I can easily do 4MB/sec using a DX33 EISA system with an AHB1742 controller > and DEC 3053L disk drives (Media transfer rate is 2.5-5.5MB/sec). This > is with FreeBSD 1.x through to FreeBSD 2.x-current, but only because the > ahb driver has been stable pretty much the whole time. I wish I had a EISA motherboard, as I have a slightly used 1742, and two 1740's laying around. Tom
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