Date: Tue, 2 Apr 1996 12:49:17 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: koshy@india.hp.com (A JOSEPH KOSHY) Cc: msmith@atrad.adelaide.edu.au, hackers@FreeBSD.org Subject: Re: HDD cpu usage (IDE vs. SCSI). Message-ID: <199604021949.MAA16832@phaeton.artisoft.com> In-Reply-To: <199604020445.AA210060355@fakir.india.hp.com> from "A JOSEPH KOSHY" at Apr 2, 96 10:15:54 am
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> ms> No, you're not understanding. For a given CPU, IDE will _always_ use more > ms> CPU time than SCSI. Period. > > I'm afraid I don't understand too; I recently had the oppurtunity to examine > a Future Domain TMC-1680 card. From what I could see this was an ISA card > with no bus-mastering capability. After the card had read in data from the > scsi bus, it would interrupt and the CPU had to use PIO to copy data from > the card to the system buffers. > > Why would card yield better CPU utilization than an IDE solution? Is this card supported? I thought no one owned these... On average, his statement is true: SCSI bus mastering is supported and IDE bus mastering is not. Non-bus-mastering SCSI is supported for people who already own crappy cards, generally for SCSI CDROM interfaces on sound cards, or old Adaptec cards sold with HP Scanjets, etc. (ie: mostly not boot devices for lack of BIOS support). > As I said earlier, there are lots of SCSI cards and disks on the market; the > cheaper ones have made quite a number of compromises in order to lower cost. > Thats the market reality. > > IMO, SCSI is not always better than IDE. "Good SCSI" is better than "good IDE". > The issue really is how much performance you are getting for your rupee. > The last time I checked here, a 1-disk SCSI sub-system cost around twice as > much as an equivalent IDE 1-disk sub-system. Become an importer and charge 1.5 times instead of 2: the costs where you will be importing from are the same. 8-). Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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