Date: Sat, 1 Nov 1997 04:18:44 -0500 From: Lee Cremeans <lee@wakky.dyn.ml.org> To: "Jamil J. Weatherbee" <jamil@trojanhorse.ml.org> Cc: chat@freebsd.org Subject: Re: IDE Drive Economy Message-ID: <19971101041844.31170@wakky.dyn.ml.org> In-Reply-To: <Pine.BSF.3.96.971031202732.751A-100000@trojanhorse.ml.org>; from Jamil J. Weatherbee on Fri, Oct 31, 1997 at 08:34:59PM -0800 References: <Pine.BSF.3.96.971031202732.751A-100000@trojanhorse.ml.org>
next in thread | previous in thread | raw e-mail | index | archive | help
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. -- Lee C. -- Manassas, VA, USA (WakkyMouse on DALnet #watertower) A! JW223 YWD+++^ri P&B++ SL+++^i GDF B&M KK--i MD+++i P++ I++++ Did $++ E5/10/70/3c/73ac Ee34/1/36 H2 PonPippi Ay77 M | hcremean (at) vt.edu FreeBSD/Linux/Unix hacker...Win95 and M$ evil! (go see www.freebsd.org) My home page: http://wakky.dyn.ml.org/~lee | finger me for geek code
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?19971101041844.31170>