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From: nic@marque.mu.edu (Nic Bernstein)
Newsgroups: comp.sys.att,unix-pc.general
Subject: Re: Re: 7300 floppy + memory query
Message-ID: <1940@marque.mu.edu>
Date: Thu, 26-Nov-87 00:42:50 EST
Article-I.D.: marque.1940
Posted: Thu Nov 26 00:42:50 1987
Date-Received: Sun, 29-Nov-87 14:49:37 EST
References: <384@gethen.UUCP> <257@ihop3.UUCP>
Reply-To: nic@marque.UUCP (Nic Bernstein)
Organization: Marquette University - Milwaukee, Wisconsin
Lines: 79
Xref: mnetor comp.sys.att:1888

In article <257@ihop3.UUCP> spear@ihop3.UUCP (Steve Spearman) writes:
>> Xref: ihop3 unix-pc.general:1167
>> In article <2848@ihlpf.ATT.COM> spear@ihlpf.ATT.COM (Spearman) writes:
>>>First, was I the only person who did not know that the floppy
>>>in the 7300 is not PC-compatible.
>> You are wrong.  The floppy in mine, and the one specified in the Tech
>> Reference Manual, is a dead standard Teac floppy, no different than
>> the one I have in my PC.  
>
>I'd be interested in feedback from anyone else who has actually put
>an IBM standard floppy in their PC.  Not only did I try a known-good
>drive from my 6300 and play with all the jumpers, but I ask an AT&T
>serviceman who verified that the 7300 floppy was NOT PC compatible.
>However the Teac drive in the 7300 is Teac FD-55B-01-U which is one I recall
>as marketed for MSDOS clones.
>
>The jumpers could certainly have been the problem - the naming schemes
>of the two letter codes on the jumpers was not the same between the
>Teac 7300 and the 6300 floppy drive, so I was just guessing and experimenting.
>Maybe someone knows the changes from a standard clone floppy setting?
>
>Also, if the drive is really PC compatible, does that mean that an
>after market 3 1/2 inch or an AT drive could be substituted?  Or would
>that be beyond the abilities of the controller to handle?
>-- 
>Steve Spearman  {ihnp4,ethos}!ihop3!spear
>Voice: (312) 979-4181

I don't see why this is impossible.  I have removed the standard Teac drive
from the pc7300 cabinet and blocked off the hole that it occupied.  I then
replaced the short cable to the drive with a long one which I ran out of
the cabinet and the power supply I extended with a power "y" cable for a
MSDOS machine, which is intended to power two drives when only one power
connector was built in.  This is long enough to reach outside the cabinet
also.  I had a spare (old) Shugart SA465 drive which is a 96tpi unit.  I
have the two drives sitting side by side next to the pc7300 with power 
avaliable to both and simply switch the data cable between the drives to
have 360K or 720K backups and archives.  I now only use the 40tpi when I
need to make MS-DOS compatable disks or need the original foundation set.
I also re-made the diagnostics and 1st set of 3 floppies in a 80 track
version so I can re-boot and re-load software from the denser 80 track
drive.  The only other change needed was to make a discriptor file for
"iv" to format the disk with.  This setup has worked well for me for
over two years now.  So I fail to see why using standard MS-DOS floppies
should be a problem.  The following has also been observed/tried:
Making the floppies with 10 sectors rather than 8, this resulted in 
un-reliable reads.  The harware does not bring out all the mutiplex lines
to the cable, so you can only have onme drive address for the floppy.
Also the descriptors arn't there (/dev/fp?).  The following information
comes from the AT&T Service Manual, a handy little book that I paid just
slightly over a buck a page ( this is if you count both sides of the 
dividers and both sides of blank pages, etc. ) as this wasd, at the
time, the only way to find out how to connect a serial port...  Fortunately
AT&T wised up and has now included the port information in th eowners manuals.
There are two sets of jumper rows on the drive.  The one closer to the data
connector:

HS  - No jumper	- Head Select
DSO - JUMPER	- Drive select 0
DS1 - No jumper - Drive select 1
HM  - JUMPER	- Head Motor Option
DS2 - No jumper - Drive select 2
DS3 - No jumper - Drive select 3
MX  - No jumper - Drive select mux

The jumper row furthest from the data connector ( Unfortunatly I don't
know the meanings of the symbols).

UR  - No jumper
ML  - No jumper
IU  - JUMPER
HL  - No jumper
SM  - JUMPER
U0  - No jumper
U1  - No jumper
RE  - No jumper

I hope this helps!
						- Nic