7300 HD Head Select Upgrade REPOST

[Craig Votava]

Here is the head select upgrade repost for the unix-pc. I have talked with
Convergent about the status of the PAL equations, and they said that they
didn't care what happens to them unofficially; officially, they will not
go to any hasstle to release the information. I take that to mean
that I can't post them to the net (which I won't), but they should be
obtainable if you're persistant enough.

/* Written 12:23 pm  Nov  9, 1987 by looney!cmv in looney:unix-pc.general */
/* ---------- "9 Head Hard Disk Working on 7300!" ---------- */
I can't believe it, it actually works!! In fact, it worked the first time no
less, with no problems, I really couldn't believe it! I actually have all
9 heads working on the hard disk drive of my unix-pc!!!

Here's the scoop:

After MONTHS of snooping around I got some very nice help from both Convergent
folks and a VAR in NJ called Computer Integration Associates, and eventually
aquired the upgrade kit to make my 7300/3b1 address more than 8
hard disk heads. I am currently talking with Convergent Technologies to find
out the proprietary status of the information they gave me, to see what we
can do about getting the stuff out to the general public. The following
description is a general overview that does not violate any proprietary status.

The actual name of the kit is "FIELD SERVICE P5.1 UPGRADE REWORK INSTRUCTIONS"
and all it consists of is 8 pages of text; one page of instructions, one page
with the PAL equations to be burned into a PAL, four pages of diagrams showing
where the jumpers go on the motherboard, and 2 pages showing before and after
versions of the schematics.

The upgrade hardware is one PAL, one capacitor and 9 jumper wires. It
consists of adding the PAL into a blank IC slot, the cap above it, then
running the jumper wires to the appropriate places. It's possible to do the
entire upgrade without removing the motherboard if you directly solder the
PAL to the board, I decided to install a socket instead, having all of the
jumpers configured off of the socket and so had to remove the motherboard to
solder the socket in properly. I did it in about 4.5 hours, being deliberately
slow and careful, and had a buddy check everything I did after I re-checked
myself a number of times. I used 30 gage wire-wrap wire, a 20-pin socket,
and solder all from Radio Shack (the cap and PAL was supplied by a friend).

The documentation says that the upgrade will only work with the 3.5 or later
versions of the operating system, and I'm inclined to believe this from some
guru's that told me about some driver masking mumbo-jumbo that was taken out
of the 3.5 code.

Before the installation, I was able to get a file system of about 50MB out
of my CDC Wren II (86MB unformatted) when I used the "other" selection of
the disk formatting menu from the diagnostic disk (3.51), telling it I had
925 cylinders and 8 cylinders/track (heads). I tried re-formatting, telling
it I had 9 heads, and the format went fine, but errors occured afterwards.
Then I did the upgrade and re-formatted again telling it I had 9 heads,
everything worked fine, so I loaded up 3.51 and ended up with a file system
of 63MB total!

The neat thing about this is that BIG drives like the MAXTOR 190MB drive
should be able to be fully utilized on the 7300/3b1 with this upgrade along
with the WD1010 to WD2010 upgrade! There are no longer limits of disk drives
with 1024 cylinders and 8 heads maximum on this machine! The VAR that I talked
to in NJ has the MAXTOR 190 available, the demo line for them is
1-800-342-5029.

Craig Votava
[ihlp4!]looney!cmv
/* End of text from looney:unix-pc.general */