PDA

View Full Version : Help identifying a couple boards in my new 5150



misterblack
August 2nd, 2017, 11:55 AM
Hey guys, I recently picked up a really rough "barn find" IBM PC 5150 complete system. It was absolutely filthy inside and out (so many dead bugs!) but I'm slowly getting it working. I'm trying to figure out a little more information about these two cards which were in it:

MFM/Floppy Controller with Z80A
https://imgur.com/a/DLTip

This MFM card is odd. It was connected to a Tandon 20meg MFM drive which spins but I haven't tried booting yet. What is odd to me is the MFM card has a Z80A processor on board which seems rather fancy. Since there doesn't appear to be any RAM on the MFM card so I don't think it would be used for CPM. It has lots of jumps on board with no labeling. I googled for the PC Limited ZM2 and only found one post on Google Groups from 1995 with someone asking for information on this card too. I'll try reading the two EPROMs and see if anything is revealing inside.

MDA/Hercules(?) Video/Printer Card
https://imgur.com/a/8ZBtO

The working MDA card seems to have 12k of SRAM on board -- which is odd. From my research, the original MDA card has 4k, and the CGA card 16k. The Hercules card had 64k of RAM. There is clearly provision for a RAM expansion daughter board but what exactly would 12k of SRAM give me? There are also 4 dip switches. The board also has an EPROM and the sticker fell off. I'll try reading in the EPROM to see if anything revealing is inside.

I'm assuming they will both work in their current state, so as long as I don't lose the "as-configured" settings, I should be OK. Thanks!

mgutzeit
August 5th, 2017, 12:35 AM
Hi... The MFM could be this one i think....

http://stason.org/TULARC/pc/hard-disk-floppy-controllers/U-Z/XEBEC-AMERICA-Two-ST-506-412-MFM-drives-1220-ASSY.html

greetings

modem7
August 5th, 2017, 04:18 PM
Welcome to these forums.


I'm trying to figure out a little more information about these two cards which were in it:
MFM/Floppy Controller with Z80A
That is a Xebec model 1220 (see [here (http://www.arvutimuuseum.ee/th99/c/U-Z/21080.htm)]) that has a custom BIOS ROM fitted (ROM labelled "PC LIMITED ZM2").

The other ROM on the controller will be for the Z80.

Xacalite
August 5th, 2017, 05:44 PM
MDA/Hercules(?) Video/Printer Card
https://imgur.com/a/8ZBtO

The working MDA card seems to have 12k of SRAM on board -- which is odd. From my research, the original MDA card has 4k, and the CGA card 16k. The Hercules card had 64k of RAM. There is clearly provision for a RAM expansion daughter board but what exactly would 12k of SRAM give me? There are also 4 dip switches. The board also has an EPROM and the sticker fell off. I'll try reading in the EPROM to see if anything revealing is inside.

Note the two crystals: 16.257 MHz, which is standard for MDA/HGC, and 18.432 MHz, which is non-standard.
Obviously it's some high-res card, probably 132-column, maybe 132x43 - this mode would require 11352 B, so they installed 12 KB as the basic option.

misterblack
August 5th, 2017, 08:43 PM
Oh wow, that is cool thanks for that. What does the BIOS do on these cards? Still rather shocked it has a Z80A just for a drive controller. I guess since the 5150 has no official HD support a card with a BIOS is totally required.

I have since booted up the machine with the included 20mb drive and it works, but I'm going to investigate the BIOS images a little more.

misterblack
August 5th, 2017, 08:46 PM
Note the two crystals: 16.257 MHz, which is standard for MDA/HGC, and 18.432 MHz, which is non-standard.
Obviously it's some high-res card, probably 132-column, maybe 132x43 - this mode would require 11352 B, so they installed 12 KB as the basic option.

Ah right. Does the company logo ring any bells? I have a Muktisync monitor which will definitely support those frequencies so would be interesting to try to get that working. The hard drive included with this machine boots but no video drivers appear to be on it.

Xacalite
August 8th, 2017, 05:46 PM
Ah right. Does the company logo ring any bells? I have a Muktisync monitor which will definitely support those frequencies so would be interesting to try to get that working. The hard drive included with this machine boots but no video drivers appear to be on it.
It must be "SuperVision" by California Computer Systems, supporting up to 132x44 text, and optionally (with the daughterboard) Hercules graphics.
Search PC Mag 5 feb. 1985 for a review.
Nice card indeed, good luck running it!

SomeGuy
August 8th, 2017, 06:05 PM
Support for cards like that were usually application specific. What software is on the hard drive? (If it still has software on it, be sure to back it up ASAP)

gertk
August 8th, 2017, 11:07 PM
BTW: the SY2158a-2 chip is a static ram chip of 2 kByte so there is some ram on that FDC/MFM HD controller card.
The Z80 needs some stack space and the rest is dedicated I guess as some sector buffer space.

misterblack
November 5th, 2018, 12:44 PM
It must be "SuperVision" by California Computer Systems, supporting up to 132x44 text, and optionally (with the daughterboard) Hercules graphics.
Search PC Mag 5 feb. 1985 for a review.
Nice card indeed, good luck running it!

You know, somehow I missed these responses! Wow that's cool -- I just read the review of the card. Too bad information is pretty much non-existent outside of the review. A manual or driver disk would be nice. Sadly the original drive didn't have anything on it that seemed related to the card, which was odd since it was so old. THere were just a couple programs on the hard drive and some home-made basic programs... it's like he never really used this machine much, or perhaps he didn't use it much after he got the hard drive and the original floppies are lost.

It would be very neat to see 132x44 text on a IBM 5151. :-)