IBM 5170

in progress RH-V7QP

IBM 5170 RH-JKDJ

0/8

Swap U43 and U44 (first 256K parity chips) for known-good chips and re-run the IBM POST. RH-JKDJ
If it persists, get sheet 10 and trace the parity logic from MDPIN/MDPOUT to U43 and U44. RH-JKDJ
Inspect the two new DRAM sockets and the U62 rework for bridges, lifted pads and damaged tracks. RH-JKDJ
Note which positions have the new sockets. RH-JKDJ
Check the SuperSoft Landmark AT manual for what "U126 8042 parity detected" actually tests. RH-JKDJ
Get a probe ROM that shows parity check (61h bit 7) and I/O check (61h bit 6) separately, with a parity test per bank. RH-JKDJ
Recheck what the POST card shows in the 201 loop (C0 against DD). RH-JKDJ
Re-run the IBM POST and SuperSoft after each change. RH-JKDJ

Nothing on order.

No files for this one yet.

2026-09-29: dropped: Have sheets 10 and 21 and the U126 sheet ready for the next session.
2026-09-29: dropped: If the 201 clears, test the old U43 and U44 on the BackBit.
2026-09-29: dropped: Paste this chat's link into the handover.
2026-09-29: dropped: look at the issues with the keyboard controller parity
2026-09-29: to do: Paste this chat's link into the handover.
2026-09-29: to do: Re-run the IBM POST and SuperSoft after each change.
2026-09-29: to do: Recheck what the POST card shows in the 201 loop (C0 against DD).
2026-09-29: to do: Have sheets 10 and 21 and the U126 sheet ready for the next session.
2026-09-29: to do: Get a probe ROM that shows parity check (61h bit 7) and I/O check (61h bit 6) s…
2026-09-29: to do: Check the SuperSoft Landmark AT manual for what "U126 8042 parity detected" act…
2026-09-29: to do: Note which positions have the new sockets.
2026-09-29: to do: Inspect the two new DRAM sockets and the U62 rework for bridges, lifted pads an…
2026-09-29: to do: If it persists, get sheet 10 and trace the parity logic from MDPIN/MDPOUT to U4…
2026-09-29: to do: If the 201 clears, test the old U43 and U44 on the BackBit.
2026-09-29: to do: Swap U43 and U44 (first 256K parity chips) for known-good chips and re-run the …
2026-09-29: status: planned → active
2026-09-29: to do: look at the issues with the keyboard controller parity
2026-09-29: took on IBM 5170 (RH-JKDJ)
2026-09-29: created