Several things

From: Mark <mark_k_at_iname.com>
Date: Sun Apr 4 15:53:14 1999

Hi,

Several different subjects in one message...



Sony 650MB 5.25" MO drive
-------------------------
I posted about this drive a couple of week ago. At the time, I thought one of
the firmware EPROMs was faulty. (It wasn't. I have backed up all four EPROMs in
the drive.) It turned out that the drive lens needed cleaning. Not having a
5.25" head cleaning disk -- these are expensive, I think IBM wants over 50
pounds for one -- I had to disassemble the drive, removing both circuit boards
to reveal the lens. After cleaning with a cotton wool bud & isopropyl alcohol
and putting the drive back together, it miraculously worked!

The surfaces of all the disks were quite dirty. I believe the drive was used in
the City of London, and years of pollution left a residue on the surfaces. I
don't have a 5.25" MO disk cleaning kit, but luckily it's quite simple to clean
5.25" disks by hand. Briefly, I did this:
 - wear plastic gloves to avoid getting oil from skin on surface
 - breath on disk surface and wipe radially with a folded-up kitchen towel
 - rotate the disk using finger (there is space to do this between the outside
   of the disc and the casing) and repeat the breath & wipe until the entire
   surface is cleaned
 - do the same for the other side

Things I learned:
 - Old MO drives and disks are sometimes available very cheaply, so it's worth
   looking out for them.
 - Cleaning the drive lens and disk surfaces can bring performance back to as-
   new. Dirt impairing performance might be a common reason why a company would
   get rid of old drives.
 - You don't need an expensive cleaning kit to clean 5.25" disks. If you're
   adventurous, you can clean the drive lens without needing to buy a special
   disk.
 - The old drives are much slower than modern ones. Performance is about
   equivalent to a 4.5x CD-ROM drive for reading, with average seek time of
   95ms (some modern drives are 20-25ms).

If anyone in the UK wants to get rid of an old 5.25" MO drive, especially a
1.3GB unit, please let me know. I'd like to have a backup unit in case my drive
breaks down.



EPROMs
------
My experience with one of the firmware EPROMs (made by TI) in the Sony drive
showed that "not all EPROMs are the same", which is news to me at least. Data
in most EPROMs can be dumped by doing this:
  - drive /OE low
  - set up address lines
  - read value on data bus

However the TI EPROM didn't like that; doing it that way, even reading multiple
times and ANDing the results, gave errors. After changing my program to set up
the address lines before driving /OE low, everything went okay. Now I need to
re-dump the various EPROMs from other things that I thought were bad.
Hopefully at least some will be okay.



C= PET VisiCalc EPROM
---------------------
The Commodore PET version of the VisiCalc spreadsheet came with a chip that
plugged into a socket on the main board. This was probably an EPROM, used for
copy-protection. I have an original VisiCalc package, minus this EPROM. Does
anyone know where I can download an image of the EPROM from?



Nutspinner
----------
Disassembling PCB-mounting D-type connectors is a pain without having a
nutspinner for the hexagonal bolt things which typically fix the connector to
a panel. What size, number or whatever nutspinner is the right one for this
purpose?



IBM 3363 WORM drive
-------------------
Along with the Sony MO drive, I picked up an IBM model 3363 WORM drive (IBM
part number 63X4146). This was made in 1987. The original product announcement
can be read on the IBM web site. It uses write-once disks which store about
200MB. Luckily it came with twelve such disks, four of which are still in
their wrapping.

Anyway, the drive uses some kind of custom interface. It connects to a special
ISA or MCA card via a cable with 37-way D connectors at each end. The drive
came with two MCA cards, part number 63X4266. I have been unable to test the
drive or cards, since I don't have an MCA machine.

Does anyone know what the part number of the ISA controller for the 3363 drive
was? And where I might get one (cheaply)?

The MCA controllers have a firmware (EP)ROM on. One uses a 27C64 EPROM, which I
was able to backup without (many) problems. The other uses what I presume is a
mask ROM, MN2364DSP; this is made by Matsushita. I can't seem to dump this
properly, so its pinout must be somehow different to the 2764 EPROM. Any ideas
where I might look to find the pinout for this chip?



Regards,
-- Mark
Received on Sun Apr 04 1999 - 15:53:14 BST