Date: Sat, 01 Nov 1997 18:52:42 +0000 From: =?iso-8859-1?Q?=DEor=F0ur?= Ivarsson <totii@est.is> To: hcremean@vt.edu Cc: "Jamil J. Weatherbee" <jamil@trojanhorse.ml.org>, chat@FreeBSD.ORG Subject: Re: IDE Drive Economy Message-ID: <345B7A7A.41C67EA6@est.is> References: <Pine.BSF.3.96.971031202732.751A-100000@trojanhorse.ml.org> <19971101041844.31170@wakky.dyn.ml.org>
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Lee Cremeans wrote: > > On Fri, Oct 31, 1997 at 08:34:59PM -0800, Jamil J. Weatherbee wrote: > > > I know that scsi is supposed > > to be better, but are SCSI drives (I mean the physical disk hardware) of > > higher quality or is it just the controller architecture that is > > deficient. > > IDE is a rather simple command set based on the old Western Digital > WD1003-WA2 and WD1007 interfaces; the first card is the original 1985 PC-AT > MFM controller card! The entire point of IDE was to make a cheap drive with > integrated controller components that would work "out of the box" with an AT > BIOS; it was developed by Compaq with help from WDC, Imprimis and Conner in > 1987-1988. IDE shares many of the WD1003's wins (the cylinder number is > 16-bit, and the sector number is 8-bit, giving a max geometry of 65536 > cylinders*16 heads*256 sectors==128 GB) and losses (not good for > multitasking since all accesses have to be serialised, and the interface is > rather piggish, even with DMA support). > > SCSI, on the other hand, is more robust and handles multi-tasking > environments more adeptly; it started in the early 1980s as SASI (Shugart > Associates Systems Interface), and was codified around 1986 as SCSI-1. SCSI > has its own command language, and can have multiple devices doing things at > once, unlike IDE where you can only talk to one drive at once. Also, the > newest versions of SCSI can outdo IDE in raw speed, which is partially due > to the smarter bus architecture. To top it off, SCSI can handle more devices > (7 for narrow, 15 for wide) at once, and isn't limited to hard drives, > unlike IDE, which was like that until ATAPI came out (ATAPI is really just a > SCSI-style protocol grafted onto the IDE/WD1003 register structure, hence > the many comments here about IDE Zip drives just being SCSI devices with > different firmware.) > > As for the drives, well, it depends. Most IDE drives these days are built > just as well as their SCSI counterparts, though there are some SCSI-only > drives that are notably wonky (the Quantum Grand Prix comes to mind; I've > heard quite a few horror stories about that drive line), and a few drives > that are just plain junk (most of the Maxtor/MiniScribe 7000 series, IDE or > SCSI, and ESPECIALLY the 7120). FWIW, the only real difference between a > SCSI drive and an IDE drive these days is the interface chip and the > firmware. > > > It is unlikely that home users will just suddenly start buying > > mass quantities of scsi interface drives, so they will probably continue > > to be inproportionately expensive. > > Well, the Mac did help with that somewhat. I noticed that when Apple started > running aground, the prices of SCSI stuff went way up (higher than what they > had been). Apple cheated in some newer Macs, tho, and used IDE; I forget > which ones exactly. All low end Macs are using IDE drives but the computer has SCSI interface, and most of the macs have SCSI CD-ROMs. The low end machines I remember are: 630 (68040),5200,5260 (60X) and more Thordur Ivarsson
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