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From: jms@tardis.Tymnet.COM (Joe Smith)
Newsgroups: comp.sys.amiga.hardware
Subject: SCSI II specs
Keywords: Big, mean, fast & shiny controllers
Message-ID: <1232@tardis.Tymnet.COM>
Date: 20 Sep 90 02:35:19 GMT
References: <3769@ruuinf.cs.ruu.nl> <14418@cbmvax.commodore.com>
Reply-To: jms@tardis.Tymnet.COM (Joe Smith)
Organization: BT Tymnet, San Jose, CA
Lines: 27

>>I believe that the method employed here is using a 16 bit wide bus (dubbed 
>>SCSI II), instead of the former 8 bits.

In article <14418@cbmvax.commodore.com> daveh@cbmvax.commodore.com (Dave Haynie) writes:
>SCSI II isn't 16 bits wide, it's still 8 bits.  It specifies the SCSI command
>set in a much more standardized fashion than original SCSI, and has a fast
>synchronous transfer mode capable of 10 megabytes/second.

I've heard that from a software point of view, SCSI-II is mainly the enhanced
set of commands that Dave mentions.  But from a hardware point of view,
SCSI-II has two options, which can be combined.

  1) Just the new commands (including better connect/reconnect) = 5M bytes/sec
     (this is copatible with SCSI-1 devices)
  2) Fast SCSI = 10 megabytes per second
  3) Wide SCSI = 16 bit transfers at 5 million per second = 10 megabytes/sec
     (SCSI-I and SCSI-II devices can co-exist on the 16-bit bus)
  4) Fast and wide = 16 bit transfers at 10 M = 20 megabytes per second.

At Sun-Expo, several companies announced plans for 16-bit SCSI-II.
No single disk produces 20 megabytes per second, but some companies are
working on disk clusters that act like a single, large, fast disk.
-- 
Joe Smith (408)922-6220 | SMTP: jms@tardis.tymnet.com or jms@gemini.tymnet.com
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