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1988 IBM motherboard

D

diego

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Dec 27, 2011
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HI,
I have this 1988 IBM PC/XT motherboard attached below. Can someone please tell me how can I get the block diagram of this motherboard. It's a bit urgent and help is greatly appriciated !
Thanks

Regards Diego.
 

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diego said:
I have this 1988 IBM PC/XT motherboard attached below. Can someone please tell me how can I get the block diagram of this motherboard.
Click to expand...
The resolution of the photo is very poor, but good enough to determine that the board is not an IBM XT motherboard. It is probably one of many clones of the IBM XT motherboard. The block diagram of the clone motherboard should be the same as (or very close to) the block diagram for the IBM XT motherboard. That block diagram can be found on page XVII (PDF page 19) of the IBM document at http://www.minuszerodegrees.net/manuals/IBM_5155_5160_Technical_Reference_6280089_MAR86.pdf

diego said:
It's a bit urgent
Click to expand...
Sounds suspiciously like homework.
 
thanks very much for you help! ...and yes it's a homework exercise about motherboards.

Regards Diego.
 
Personally I'm interested in the question too, but not in a negative way.

OP, please do post back some more info on the nature of your course and how this question has arisen! This kind of thing would be unlikely to come up in a UK school at the moment, judging by recent press coverage anyway.
 
IBMMuseum said:
I'm interested in why there is only two I/O bus connections populated on the motherboard...
Click to expand...
Usually when you see them like that they were used with a riser (or two) to mount the cards sideways for shorter cases. A few makers (like Packard Hell) used the same boards (making one type of board cheaper than two) and just populated them different depending on which case they were going into.
 
deathshadow said:
Usually when you see them like that they were used with a riser (or two) to mount the cards sideways for shorter cases. A few makers (like Packard Hell) used the same boards (making one type of board cheaper than two) and just populated them different depending on which case they were going into.
Click to expand...

I've got one clone case that does that (mine with a generic 386DX-40 motherboard, and two ISA risers), but mine had all of the adapter connections...

Thank You for the clarification...
 
Well it's interesting in that it appears to be a UK designed & produced board. The missing slots are a puzzle however.

g.
 
It may have been a budget board model, although the inclusion of a V20, sockets for virtually every chip and two crystals would suggest otherwise.

It may have 640K if the first bank had 512kx1 and the second and third banks at 64kx1 chips.
 
And, a little news tidbit from July, 1986 InfoWorld:

LONDON - IBM reportedly told Computoprocessing Ltd., maker of the Compro 88 PC Clone, that the Compro 88's basic input/output system (BIOS) contains a substantial part of the IBM PC's BIOS and thus is in violation of IBM's copyrights...
Click to expand...

An interesting read...

A little on the company--finally dissolved in 1993 Evidently, BT had oardered 1,000 of their systems when the whole deal collapsed after the IBM allegations. It appears that the firm's directors all resigned in 1986 as a result. (using a bit of Google-fu).

I think it's interesting that the motherboard's ICs are socketed throughout.
 
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LONDON - IBM reportedly told Computoprocessing Ltd., maker of the Compro 88 PC Clone, that the Compro 88's basic input/output system (BIOS) contains a substantial part of the IBM PC's BIOS and thus is in violation of IBM's copyrights...
Click to expand...
Ya', looks like a case of too much firmware and not enough hardware in this item! :smile:
 
Chuck, some of the stuff you post is so interesting from the point-of-view of micros in the '80's. Love this, from the above,

Micros here are very expensive. Beeb with printer would be between $NZ1800-3000 (£800-1200). So I use a Burroughs mainframe
Click to expand...
 
Great Hierophant said:
It may have been a budget board model, although the inclusion of a V20, sockets for virtually every chip and two crystals would suggest otherwise.

It may have 640K if the first bank had 512kx1 and the second and third banks at 64kx1 chips.
Click to expand...

I'm sure that you're right on that item--I suspect that there were PALs or ROMs or jumpers that selected between the two configurations. At a later time in the XT clone's history, 64Kb chips offered no particular cost advantage over 256Kb ones. Another approach was to use 2 rows of 256Kb chips followed by some 64Kx4 chips and one 64Kx1 for parity to save some real estate.
 
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