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From: djh@neuromancer.metaphor.com (Dallas J. Hodgson)
Newsgroups: comp.sys.amiga
Subject: Re: SCSI vs. ST506 vs. ESDI vs. Whatever else there is???
Keywords: SCSI ST506 MFM RLL ESDI HARD DISK DRIVE
Message-ID: <1449@metaphor.Metaphor.COM>
Date: 20 Sep 90 18:55:04 GMT
References: <Sep.19.12.05.42.1990.26653@dimacs.rutgers.edu>
Sender: news@metaphor.Metaphor.COM
Reply-To: djh@neuromancer.metaphor.com (Dallas J. Hodgson)
Distribution: usa
Organization: Metaphor Computer Systems, Mountain View, CA
Lines: 43

In article <Sep.19.12.05.42.1990.26653@dimacs.rutgers.edu> srm@dimacs.rutgers.edu (Scott R. Myers) writes:
>
>Okay I'm tired of being in the dark about all of this different Hard
>Disk interfacing.  I've worked with IBM, Mac and Amiga and everyone
>seems to do it different.  I've got IDE MFM ESDI Hocus Pocus on the
>brain.  Can some of the netlanders shed some light on What all of
>these Acronyms mean but more importantly for my knowledge which is the
>better performer and why.  Thanx in Advance!!!

ST506: The standard IBM-PC controller standard, invented by Seagate (or was
       it Shugart?) Basic Premise: Cheap; the hard drive smarts are in the
       controller card.
RLL  : "Run Length Limited", a slightly different version of the above that
       uses smarter compression technology to increase the recorded bit-
       density. RLL drives are identical, but "certified" as RLL. The
       controller card makes the difference.
ESDI : The highest-performance hard drive standard in popular PC use. A much
       more thought-out, higher-performance standard. Twice the bit density
       of standard ST506 drives. Up to 1.5mb/sec transfer rate. The drives
       are a bit smarter. Special controller card required. "ESDI = Enhanced
       Systems Data Interface", I believe.
SCSI : A kind of generic hardware protocol where many devices of different
       types can be daisy-chained together and communicate with each other
       in a standard fashion. SCSI-II is the latest improved spec, which
       allows SCSI hardware to talk amongst themselves, among other things.
       Most of the smarts are in the peripherals themselves; the controller
       cards are simple in comparison. Max transfer rates can be comparable
       to ESDI, but this depends on the implementation.

ST506 (PC) and SCSI (Non-PC) are the most popular microcomputer drive
formats. There are more formats than this, but you don't see 'em in the
(comparitively low-performance) microcomputer industry.

Anybody remember the first Amiga hard drive? The A-1000 SASI interface
drive from Tecmar. What a $1000 20-MB failure!
+----------------------------------------------------------------------------+
| Dallas J. Hodgson               |     "This here's the wattle,             |
| Metaphor Computer Systems       |      It's the emblem of our land.        |
| Mountain View, Ca.              |      You can put it in a bottle,         |
| USENET : djh@metaphor.com       |      You can hold it in your hand."      |
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