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From: boyd@nu.cs.fsu.edu (Mickey Boyd)
Newsgroups: comp.sys.atari.st,comp.sys.atari.st.tech
Subject: Re: Weird TT hard disk thingy
Message-ID: <1991May1.143101.3904@mailer.cc.fsu.edu>
Date: 1 May 91 18:41:38 GMT
References: <2910@atari.UUCP> <1991Apr24.153245.19616@unx2.ucc.okstate.edu> <2917@atari.UUCP>
Reply-To: boyd@nu.cs.fsu.edu (Mickey Boyd)
Organization: Florida State University Computer Science Department
Lines: 65


In article <2917@atari.UUCP>, apratt@atari.UUCP (Allan Pratt) writes:
Newsgroups: comp.sys.atari.st,comp.sys.atari.st.tech
Subject: Re: Weird TT hard disk thingy
References: <2910@atari.UUCP> <1991Apr24.153245.19616@unx2.ucc.okstate.edu> <2917@atari.UUCP>
Distribution: 
Followup-To:
Reply-To: boyd@nu.cs.fsu.edu (Mickey Boyd)
Organization: Florida State University Computer Science Department

In article <2917@atari.UUCP>, apratt@atari.UUCP (Allan Pratt) writes:
>cummins@unx2.ucc.okstate.edu (John Cummins) writes:
>>The fellow you've been chatting with says the TT won't recognize SCSI devices
>>1-7 on the ASCI bus, at least not without an SCSI 0 in place.  Device 0 MUST
>>be used for the first device.  Why????
>
>[Am I "the fellow [he's] been chatting with"?]
>

No, I am.

>I can't speak for what SCSI unit numbers ICD or Supra adaptors will or
>won't recognize.  From the data presented here, it sounds like ICD will
>handle any SCSI unit number on the drive, and Supra will only talk to SCSI
>unit zero. The latter is not unreasonable -- if you've got only one drive
>on a SCSI-to-ACSI converter, why include the logic to talk to an arbitrary
>SCSI device number?  It would mean logic in the adaptor to see what SCSI
>drives are out there.

No, both the Supra and the ICD will allow for the absence of a SCSI device
number 0 (ie they both support muliple devices).  

>As for the ST/TT side of the bus, you have to start with zero on each bus
>and increment by one for each drive you connect to that bus.  (Remember,
>that's unit numbers as the computer sees them, not as the adaptor sees the
>disk it's actually talking to.)  The reasons for this are kind of involved,
>and I don't want to go into them; just take my word for it and carry on.
>

The reasons for this have always been the exact question which I have been
asking.  At this point, an explination does not interest me.  However, I 
do think it would be rather nice if a paragraph or two was included in the
TT manual explaining this phenomena, and how to correct it with a few of 
the major brands of host adaptors.  The DMA port on the back of the TT 
is handled differently than that on the various ST's, and this could cause
an hard drive set up (and working) on an ST to fail (with very little 
explanation from the Atari HD software).   

>I have even heard of some adaptors which look at the SCSI unit number of
>the drive that's connected, and configure themselves as that ACSI unit
>number, further confusing the issue.
>

This is very likely the reason why the drive did not work.  Since the 
SCSI disk was set to ID 1, perhaps it set the ASCI number to the same
(thus confusing the Atari HD software).  It would be interesting to 
see if the BMS and ICD host adaptors create the same problem.

--
    ---------------------------------+-------------------------------------
             Mickey R. Boyd          |  "Kirk to Enterprise.  All clear 
          FSU Computer Science       |      down here.  Beam down    
        Technical Support Group      |      yeoman Rand and a six-pack . ."
      email:  boyd@fsucs.cs.fsu.edu  |               
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