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snuci
September 20th, 2017, 04:16 PM
Just wondering if someone knows if this equates to a PS/2 model 80?

40895

Here's a link to a bigger image: http://vintagecomputer.ca/wp-content/uploads/2017/09/IBM-PS2-planar.jpg

luckybob
September 20th, 2017, 04:30 PM
if I read the oscillators correctly, it is a 20mhz 386. so I would say yes, it is from an model 80

krebizfan
September 20th, 2017, 04:36 PM
Looks like it. Would need a closer picture to read the chip dates to be sure which model it is.

snuci
September 20th, 2017, 04:44 PM
Looks like it. Would need a closer picture to read the chip dates to be sure which model it is.

The link I posted after the picture is a bigger, more detailed image.

snuci
September 20th, 2017, 04:50 PM
if I read the oscillators correctly, it is a 20mhz 386. so I would say yes, it is from an model 80

Thank you. This is actually the main board from an IBM 7785 better known as the "Mopar Diagnostic System". I have the "Hardware Maintenance Reference/Service" manual as well but it doesn't say what PS/2 model this was the same as. I assume it is not custom but maybe an existing slightly modified board. The reference disks I have in the back of the manual only say "IBM 7785". I also have most of the parts but not the case. The case is ridiculously heavy and was just too crazy, cost wise, to ship.

Edit: It looks like this for reference:

40896

bobba84
September 20th, 2017, 05:01 PM
It's huge! I forgot how big the model 80's were. I saw a guy chuck one off a balcony once about 20 years ago, I was furious with him because I wanted it.

bobba84
September 20th, 2017, 05:02 PM
Also, I just realised something! The power connector looks strikingly similar to the one used on a wire wrap test of the 5150 motherboard pictured here (http://doi.ieeecomputersociety.org/cms/Computer.org/dl/mags/co/2011/08/figures/mco20110800191.gif)!

luckybob
September 20th, 2017, 05:12 PM
Thank you. This is actually the main board from an IBM 7785 better known as the "Mopar Diagnostic System". I have the "Hardware Maintenance Reference/Service" manual as well but it doesn't say what PS/2 model this was the same as. I assume it is not custom but maybe an existing slightly modified board. The reference disks I have in the back of the manual only say "IBM 7785". I also have most of the parts but not the case. The case is ridiculously heavy and was just too crazy, cost wise, to ship.

Edit: It looks like this for reference:

40896


makes sense really. Why design a whole new mainboard when a stock one will do fine? The power connector is the same as my model 80. The number of slots look right, the placement of the floppy drive cable connector, the ram slots look right. the 6 pin battery/speaker connection is in the right place.

now the BIOS may be different. But that is something I would believe is easily remedied.

snuci
September 20th, 2017, 05:26 PM
Without knowing the architecture, I wasn't sure if this might be PS/2 based or possibly RISC (RS/6000) based. I guess we now know. Another weird PS/2 :)

krebizfan
September 20th, 2017, 05:35 PM
The FRU number is the same as the 20 MHz Model 80 planar so there should be zero difference between them.

snuci
September 20th, 2017, 05:45 PM
The FRU number is the same as the 20 MHz Model 80 planar so there should be zero difference between them.

Thanks for confirming. I guess I can hook up the hard drive to a PC and check out the software. It appears I have CDs in two CD ROM drives as well. Those should be the reference CDs for the Mopar Diagnostics software that might get changed out between model years. I don't have a PS/2 Model 80 but did get the original power supply as well so I should be able to fire this up. Another project for the pile I already have.