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billdeg
June 19th, 2017, 04:59 PM
I have a Donatec (never heard of this company) RAM board for the IBM XT. It has a bunch of jumpers and one 6 post switch array. No model number nor part number (there is a small 821114 on the back(doubt it's a date stamp given chip date codes ~= 1985). The board is populated with 54 4164 chips (8+1 parity) 64Kx6=384K. So, when added to an XT with 256K populated on the motherboard it should be 640K.

When I play around with the jumpers on the card I can get 320K and 384K and 256K to post when the XT boots up, but not a full 640K. Anyone have a Donatec RAM board manual of any kind, especially one with one 6 switch jumper?

http://www.vintagecomputer.net/donatec/donatec_RAM-4164s.jpg

http://www.vintagecomputer.net/donatec/donatec_RAM-logic.jpg

If I find the magic combo I'll post it here. Disclosure: I plan to sell this card with an XT system I plan to put on Ebay. So you're helping me sell an IBM XT system with hopefully a full 640K. I could just put a AST card in there but what fun is that?

Bill

billdeg
June 19th, 2017, 06:14 PM
follow up, I am guessing [down down up up up down] is the correct setting, but with these settings the XT system generates a parity RAM error: 30000 00 201 The ram banks start with 1 so I assume 30000 = bank 3 and the 00 indicates a parity error (I think), otherwise there would be a value in the 2nd part of the error code (right?). 201=RAM error. I have the docs and A+ book to look it up to be sure. It'd be faster to test the RAM in bank 3 individually (I have a tester) and locate the bad chip that way rather than research my Hardware ref manuals. They don't see the forest through the trees I find.

With the card removed the system POSTs without error, 256K (64-256K board fully populated) and no errors.

My computer archeology opinion: The orig owner must have seen the error with the donatec card and bypassed problem temporarily by jumpering the DONATEC RAM expansion card to use the first 128K (bank 1 and 2) only, and was satisfied with that. Explains why the system does not attempt to count / post to 640K. My fishing around for jumpers exposed the original problem.

I put in an new RAM card rather than take this further; a no-name RAM card is worth more to me as a source of spare 4164 RAM chips. I have a dozen or more RAM cards on hand here. I am working to clear out some spare IBM PC parts, now is a good time to ask if you need anything. I bought boxes that fit the IBM PC perfectly to reduce shipping costs.

Bill

T-Squared
July 30th, 2017, 10:43 PM
I also noticed some corrosion on that barrel battery. Could that be part of the problem?

I've also seen Terry Stewart (a.k.a. tezza) find success in managing chip problems by using a piggyback method (i.e. bending the pins on a known good chip just so that they contact the pins of a bad chip, in effect taking the place of the bad chip).

billdeg
July 31st, 2017, 11:59 AM
thanks. The goal of my post was not to repair, but to get documentation on the jumpers. The battery corrosion is negligible (but quite dead), but if the battery was the issue the problem would be local to the battery and not a specific bank of RAM IMHO. Either way, I moved on, found a replacement RAM card.

evildragon
July 31st, 2017, 04:57 PM
Actually it looks like the corrosion has eaten some of the traces elsewhere. I see far too much pitting on the traces...

modem7
August 3rd, 2017, 10:38 PM
thanks. The goal of my post was not to repair, but to get documentation on the jumpers.
I found a card that appears to be the same - the Diamond Flower MF-100.
Take a look at the MF-100's component layout, shown on page 18 (PDF page 13) within the manual at [here (http://minuszerodegrees.net/manuals/DFI/Diamond%20Flower%20MFPLUS%20and%20MF-100%20-%20User%20manual.pdf)].

billdeg
August 4th, 2017, 04:35 AM
I agree, this must have been an early Japanese clone / response to the SixPak type cards resold/OEM ... great sleuthing. I uploaded a copy of the PDF to here for anyone who has the same card:

http://www.vintagecomputer.net/donatec/

I guess its historical significance is that according to the document the card is for PC DOS 1 and 2 (no reference to Microsoft or IBM), thus it must be pretty early utility card historically vintage to any of the earliest PC Clones, such as the Compaq portable, Colombia, Eagle.

modem7
August 4th, 2017, 02:54 PM
I agree, ...
The manual was supplied by member jh1523.
Software at [here (http://minuszerodegrees.net/manuals.htm#DFI)].