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From: jlohmeye@entec.Wichita.NCR.COM (John Lohmeyer)
Newsgroups: comp.periphs,comp.unix.wizards
Subject: Re: query: new disk drive for VAX
Message-ID: <297@entec.Wichita.NCR.COM>
Date: 9 Oct 88 01:43:58 GMT
References: <4198@bsu-cs.UUCP> <3531@phri.UUCP> <10199@eddie.MIT.EDU> <18529@uflorida.cis.ufl.EDU> <10209@eddie.MIT.EDU> <4559@lynx.UUCP> <4329@polya.Stanford.EDU>
Reply-To: jlohmeye@entec.UUCP (John Lohmeyer)
Organization: NCR Corporation, Wichita, Kansas
Lines: 34

In article <4329@polya.Stanford.EDU> kaufman@polya.Stanford.EDU (Marc T. Kaufman) writes:
>In article <4559@lynx.UUCP> m5@lynx.UUCP (Mike McNally) writes:
>
>>One interesting thing about Maxtors: we have a 5.25 inch full-height 
>>SCSI drive (170MB).  It only responds to the "test unit ready" command
>>when it's ready; otherwise, the command isn't acknowledged.  Think
>>about it.
>
>From ANS X3.121-1986 (p.62):
             ^^^
This should be "X3.131-1986".

>  "The TEST UNIT READY command (table 7-2) provides a means to check if the
>logical unit is ready.  This is not a request for a self test.  If the logical
>unit would accept an appropriate medium-access command without returning
>CHECK CONDITION status, this command shall return a GOOD status."
>
>See -- it says nothing about what to do if the drive is not ready :-)
>I expect that the correct response would be BUSY.

Actually, the correct response is CHECK CONDITION status with a sense key
of NOT READY.  There used to be a statement in the draft SCSI standard right
after the one about not being a self test that said, "A fast response is
expected."  This sentence was dropped because no one really wanted to define
"fast" and the sentence didn't mean much without such a definition.

I definitely agree with the sentiment that Maxtor blew it on this one -- it
certainly was not the SCSI committee's idea that a device not respond merely
because it wasn't ready. (I strongly suspect that Maxtor is retrieving
their controller microcode from the disk--thus they can't respond to SCSI
commands until the disk is ready. They should have put in a bit more in ROM.)

John Lohmeyer    j.lohmeyer@wichita.ncr.COM
.