IBM PS2 Model 80 Schematics

The PS/2 Model 80 schematic set is twenty sheets of circuit diagrams for the PS/2 Model 80 (8580), Revision 1, dated 16 October 1991.

Every sheet names the planar it was drawn from: IBM part number 90X9152-01. That matters — the Model 80 shipped with more than one planar type over its life, and these sheets document one of them. Check the number on your own board before trusting a designator.

These sheets are not an IBM publication. Every title block carries the name Maintenance Information Technologies and the words "COPYRIGHT APPLIED FOR", together with this notice:

"Servicing of any electronic product should only be performed by qualified personnel. This drawing and information has been Copyrighted by the company listed. Its content has been sold for the unlimited use to you. The only restrictions are that it not be copied for republication or distribution outside your company. No patent liability is assumed with respect to the use of information contained herein. Maintenance Information Technologies believes the information herein to be correct. We are not responsible for any typographical errors; no direct or implied warranty is made to its accuracy. Specifications subject to change without notice."

Maintenance Information Technologies was a third-party publisher of service schematics for the independent repair trade in the late 1980s and early 1990s. IBM itself never published a PS/2 schematic.

What it contains

Twenty sheets, each headed "PS/2 80" and "90X9152-01", marked "SHEET n OF 20":

1. BUS
2. CPU
3. VIDEO I/F
4. MEMORY
5. CLOCKS
6. INTERRUPTS
7. SERIAL I/O
8. PRINTER I/O
9. KEYBOARD I/F
10. DISK I/F
11. REAL TIME CLOCK
12. DMA I/F
13. BUS CONNECTORS A
14. BUS CONNECTORS B
15. I/O CONTROL
16. PALS
17. BUS SIGNALS
18. PALS B
19. PALS C
20. PALS C (continued)

Four of the twenty sheets are given over to the PAL equations, which is unusual and useful: the Model 80 planar's glue logic is in programmable arrays, and without those sheets a signal trace simply stops at the device.

What it does not contain

No text layer. These are scanned drawings. `pdftotext` returns almost nothing and OCR returns garbled fragments, so read them as page images, not as text.

No parts list, no bill of materials, no board silkscreen map and no power distribution sheet. The component values that are shown are the ones drawn on the signal circuits themselves. Bulk electrolytics and the planar decoupling do not appear, so these sheets will not give you a recapping list — but they will give you the value of a specific resistor or small capacitor in a circuit you are tracing, which is more than any IBM publication does.

There is no revision history and no statement of which planar revision a Model 30 or Model 50 sheet was drawn from.

What it settles

Together with the April 1987 technical reference, this set gives the Model 80 both ends of the documentation range that IBM machines usually lack: IBM's own power supply and interface specification, and a third-party drawing with designators and values on it. The schematics apply to planar 90X9152-01 specifically.

Download it here: IBM PS2 Model 80 Schematics.pdf

Related pages

• IBM PS/2 Model 80 · IBM PS/2 Model 80 Maintenance Guide · IBM PS/2 Model 80 Troubleshooting Guide · IBM PS/2 Model 80 Capacitor Replacement Guide
• IBM PS2 Model 80 Technical Reference (April 1987) · IBM PS2 Model 80 Technical Reference (October 1990)
• IBM PS2 Model 30 Schematics · IBM PS2 Model 50 Schematics