IBM PCjr Technical Reference
The IBM PCjr Technical Reference (Hardware Reference Library), Revised Edition, November 1983, is the 572-page technical reference for the IBM PCjr (4860).
What it contains
edit- Section 1, Introduction.
- Section 2, Base System (2-1) — the 8088 and its support devices; the 8259A interrupt controller and the PCjr interrupt assignments (2-13 to 2-17); the ROM subsystem; the input/output channel (2-21) and the input/output interfaces (2-29) including the 8255 bit map (2-30); the video and graphics subsystem (2-39 onwards) with its major component definitions, the palette (2-50), alphanumeric modes (2-54), graphics modes (2-55), the video gate array (2-63) and the CRT/processor page register (2-79); the keyboard; and the remaining on-board interfaces.
The PCjr's architecture is unlike the 5150's in several ways that matter to a repairer — the video gate array, the page register and the interrupt assignments in particular — and this is the only manufacturer document that describes them.
What it does not contain
editNot a service manual: no FRU part numbers, no removal procedures, no symptom-to-FRU index and no fault codes. No text layer in the scanned sections, so searching is unreliable; work from the section and page numbers.
There is no component-level parts list. The power brick, the internal power board and the sidecar power arrangements are described functionally and by connector, not by component.
What it settles
editIt is the primary source for the PCjr's video gate array and palette registers, its cartridge and sidecar interfaces, and its infrared keyboard protocol — the three parts of the machine most often described wrongly from memory.
Download it here: IBM PCjr Technical Reference.pdf