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From: doug@marque.UUCP
Newsgroups: comp.sys.att
Subject: Re: PC7300 schematics?
Message-ID: <1720@marque.UUCP>
Date: Wed, 8-Jul-87 20:44:24 EDT
Article-I.D.: marque.1720
Posted: Wed Jul  8 20:44:24 1987
Date-Received: Sat, 11-Jul-87 16:21:50 EDT
References: <5774@pitt.UUCP>
Reply-To: doug@marque.UUCP (harris, douglas)
Distribution: na
Organization: Marquette University, Milwaukee, WI
Lines: 55

In article <5774@pitt.UUCP> hoffman@pitt.UUCP (Bob Hoffman) writes:
>Are the schematic diagrams available for the PC7300?  If so, what
>does one order to get them?
>
>I see a listing in the 3.5 upgrade kit for a Technical Reference Manual
>for $300+.  Having been burned for $150 for the service manual, I
>hesitate to plunk down more cash just to be disappointed.  Does anyone
>have this manual?  What's in it?  Is it worth the investment?
>

I am posting rather than mailing in the belief that others might find the
information useful.

I have the "AT&T UNIX PC Reference Manual" (999-300-1891S : can't remember
if this is Com-Code or something else, but its the number on the cover:
price around $300 unfortunately.  It has schematics: several schematics
purporting to cover the same bus in fact, but no explanation of how the
signals leave the motherboard on one pin, and hit the expansion board on
a different pin :--).  I have a more or less complete "ohmeter" map I
will mail upon request.

The front page of the manual also says "A Unix PC Expansion Bus
Specification" can be obtained (for the purpose of development of
UNIX PC hardware enhancements) by writing:
   AT&T Information Systems
   UNIX PC Product Management
   1776 on the Green
   Morristown, New Jersey 07960
   (201) 898-6000
It also states that this manual is intended solely for use by qualified
service personnel to assist in maintaining the Unix PC.  (Glad I didn't
get the SERVICE manual :--).  Its hard to say whether I would recommend
its purchase or not: it has a lot of information about some things, and
is skimpy on others that seem more important (sounds like all manuals,
but for $300++?).

BTW for those that have asked it appears that hardware only allows a single
floppy and a single hard disk: there are 3 head_select bits for the hdisk,
a bit to select the hdisk, a bit to select the fdisk, a bit to turn the
fdisk motor on, and one bit each to reset the fdisk and the hdisk.
(I haven't confirmed this with actual wiring check yet :-).  These are
accessed through the "disk control register" at address 4E0000.

While I "have the floor" I'll add a reply regarding a potential
misunderstanding of an earlier posting of mine: my advice regarding
the UnixPC at its current prices is BUY, BUY, BUY.  And when you do
"clean up" the software please remember me and mail or post the fixes :--).
My "negative" remarks were in response to the question regarding the
lack of success of the product in the marketplace, and my opinion that
the "uncertain" OS is to blame.  Of course having seen the hardware more
carefully, it is irritating to say the least that on a machine with
a 32bit processor, 99 pin expansion bus, and a carefully thought out
system of hardware slots and DMA on expansion boards, they could only
allocate a single lousy 8bit register to control ALL disk access:
this seems especially odd on a UNIX box, with its wellknown disk demands.