Hard Disk Cylinder Access Upgrade REPOST

[Craig Votava]

Here's the repost for allowing your unixpc to access more than 1024 cylinders
on a hard disk. One thing to note, the latest suffix for the WD2010 controller
chip (according to Joe Hall, Thanks Joe!) is BPL05, a good thing to remember
when ordering the thing.

/* Written 10:06 am  Sep 18, 1987 by looney!cmv in looney:unix-pc.general */
/* ---------- "Hard Disk Upgrade Part 1" ---------- */
Well folks, round one of the Hard Disk Upgrade wars is now over, and things
are looking pretty good (I would NOT have said this 4 days ago)!

First of all, I'd like to thank everybody that responded to my last note
about upgrading the unix-pc to handle bigger, and better hard disks. There
was a LOT more interest than I expected. I will continue posting my results
to the net so that everybody get's to review them.

OK, on to business -- 

The unix-pc from the factory, can only address a hard disk with a maximum of
8 heads, and 1024 cylinders. I've been trying to find a way around this, and
I believe I've succeeded on the 1024 cylinders part.

The Hard Disk controller chip that the factory put's in your machine is a
Western Digital controller chip called the WD1010. This chip is the limiting
factor on the number of cylinders; the formatting software and the drivers
are open ended (so I've been told) and will try to format and/or address to
any cylinder they're requested to. The problem is that the 1010 chip cannot
handle more than 1024 cylinders on a hard disk.

Western Digital has another Hard Disk controller chip available called the
WD2010, which is pin compatible with the WD1010 in the unix-pc. This chip
costs about $70.00 (in the Chicago area), and when it replaces the 1010 in
the unix-pc, will allow more than 1024 cylinders to be addressed.

Now, the reason that this is good is because there are a number of ST-506
half-height drives that are coming out (some are already out) that have from
80 to 170 Megabytes of storage on them. Typically they have 4 heads, which
means that they have a whole lot of cylinders. If you buy one of these and
install the WD2010 in your machine, you should be able to use all the storage
with no problem.

OK, enough of the sales pitch. Here's how you install the chip. It's a piece
of cake! All you have to do is remove the 4 screws holding the cover/monitor
piece to the base (2 in the back and 2 under the covers of those little nubs
that the keyboard rests on -- lift straight up, then tilt back so the back
of the monitor rests on the table), you are now looking at the power supply
board, your hard disk drive, and your floppy disk drive. Next take out the
3 screws holding the metal cover down that these 3 things are sitting on.
Before lifting the cover (it opens like the hood of a car) unplug the power
connector on the far right (and bend it away), then unplug the video cable on
the far left (follow it down from the monitor). Make sure you have something
to prop up the lid once you open it. OK, now open the lid and prop it up. Make
sure you don't open the lid too far, or you will start bending the clamp that
holds the video cable down. What you see before you is the motherboard. If you
follow the cables from the disk drives, you'll see where they connect to the
motherboard. In-between the Hard Disk and Floppy Disk cables and a little
forward, you'll see a series of socketed (yes, thank God!) 40 pin chips, find
the one that is labelled something like "WD1010A-PL" -- that's the hard disk
controller chip. Now carefully remove that chip and install the new 2010 chip,
always double and triple checking that you're doing the right chip, that
you're not bending any of the chip leads, and that you have the chip pointed
in the right direction (all of the chips on the motherboard face the same
way). Now close everything up (make sure you remember to re-connect both the
power cable and the video cable before you're done) and run the Hard Disk
diagnostic to check and make sure everything is ok.

I installed the WD2010 on 2 different system configurations. The first was
a stock 7300 with the factory 20M hard disk in it, and everything worked
flawlessly. Next, I installed it on my system with a 86M CDC Wren II, and
I had problems. After talking around to some people, I found that the CDC
drive has been found to be flaky sometimes in the unix-pc and nobody knows
why (this is another story) so I put my WD1010 chip back since the CDC only
has 925 cylinders anyway. It's important to note that I have not been able
to test out the claims that this chip change will in fact, allow you to
use more than 1024 cylinders, all I've been able to check is that it will
work with the stock 20M hard disk. If there is anyone out there that can
verify it will work with a disk having more than 1024 cylinders, please post
it to the net. I've been told by one person that this works in his machine, I'd
like independent confirmation.

As far as addressing more than 8 heads, things are looking promising, stay
tuned for more details.

Craig Votava
[ihnp4!]looney!cmv
/* End of text from looney:unix-pc.general */