Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!evax!utacfd!merch!cpe!adaptex!adaptx1!neese
From: neese@adaptx1.UUCP
Newsgroups: comp.periphs.scsi
Subject: Re: SCSI vs. SCSI-II
Message-ID: <283400068@adaptx1>
Date: 11 Mar 91 17:42:08 GMT
References: <26822@remus.rutgers.edu>
Lines: 38
Nf-ID: #R:remus.rutgers.edu:26822:adaptx1:283400068:000:1608
Nf-From: adaptx1.UUCP!neese    Mar 11 09:15:00 1991


>/* ---------- "SCSI vs. SCSI-II" ---------- */
>
>What is the difference between SCSI and SCSI-II?
>
>(My guess: SCSI is 16bit and SCSI-II is 32bit).

Nope.  SCSI-1 is 8Bit and so is SCSI-2.  SCSI-2 allows extending to
a wider bus, but it was the cable and connector are still in the air.
Should be resolved in SCSI-3.

>Is it worth it to get SCSI-II over SCSI?  How much of a price
>difference are we talking about?  How much of a performance
>improvement?

Potentially, there is performance to be had with SCSI-2.  But all the
performance *options* in SCSI-2 may not be implemented in any particular
SCSI-2 device.  FAST SCSI (i.e. > 5MBytes/sec), tag queuing and such things
are all optional in the SCSI-2 spec.  A device can be SCSI-2 and not implement
any of these types of options.  In this case, you get nothing more than a
better implementation of the SCSI command set.
One of the biggest reasons to be concerned about a SCSI-2 implementation
is in the areas other than disk drives.  It was in this area SCSI-1 failed
to deal appropriately with these devices.  This is what I get excited about
when I think of SCSI-2.  Finally, a defination for tape, CD-ROM, WORM,
magneto-optical, juke-boxes, printers, communications devices, and processors.

>(NOTE: I will be plugging it into a 32bit machine and I want the
>fastest (but affordable) setup).
>
>I am considering $850 for a 210MB Quantum SCSI at the moment.

Good choice.  Quantum has historically had one of the best implementations
of the SCSI bus/command set.

			Roy Neese
			Adaptec Senior SCSI Applications Engineer
			UUCP @  neese@adaptex