Editing IBM PALM processor (section)

== Known Gaps in Documentation ==

This article documents PALM at the level supported by publicly available primary and reverse-engineering sources. The following details are documented in IBM's CE manuals but '''not'''  transcribed into any widely-mirrored secondary source, and remain open gaps:

# '''Function-block to gate-array mapping.''' The 13 Dutchess gate array part numbers are identified on this page (see [[#Identified ICs on the PALM Board|Identified ICs on the PALM Board]] above), but '''which function each chip implements''' (ALU, register file, microcode sequencer, bus interface, etc.) is documented only in IBM 5100 MIM SY31-0405 §4 "Theory" / "5100 Controller Description" and IBM 5120 CSLM SY34-0193, '''neither of which uses the term "PALM" or names individual gate-array part numbers'''. SY31-0405 §4 documents the function blocks as named signals (RDR, SAR, Op Reg, SDR, ALU Reg, ALU, Control ROS Unit) but stops short of saying "function block X is implemented by chip part-number Y". Closing this gap requires direct gate-level tracing of the controller card against the CSLM logic flowcharts.
# '''Function of the small 210086-C / M-210086-C DIPs.''' The part numbers are now recorded from the J2 card photograph but the function within the controller is not documented in any source the wiki has access to. The 7825 / 7828 date codes (weeks 25 and 28 of 1978) confirm the J2 card was built mid-1978, consistent with a 1978 5110.
# '''Exact System/360 instruction subset emulated.''' The canonical source is Corti's `aplros.asm` (the disassembled APL executable ROS) at `ftp://ftp.informatik.uni-stuttgart.de/pub/cm/ibm/ibm5110/`. No source enumerates the subset as a discrete instruction list. The previous version of this page identified the emulator as "System/370" — that claim is incorrect; direct disassembly shows only S/360 opcodes.
# '''Exact System/3 Model 6 instruction subset emulated by the BASIC ROS.''' Same status — emulator exists, opcode list not published.
# '''Die-shot or photomicrograph of a Dutchess masterslice.''' None located publicly.
# '''Use of PALM in other IBM products as an embedded controller.''' Wikipedia speculates ("It is likely PALM was also used in other IBM products as an embedded controller") but no source has identified a specific product. Speculation on Hacker News thread 14483823 about the '''IBM 3274 cluster controller''' is anecdotal (vt240 noted "square metal cans, many of them socketed" matching the visual signature of IBM masterslice modules of the period) but '''unverified''' against IBM documentation.
# '''Exact PALM board dimensions, weight and per-card power draw.''' Y1 power-feed cable on the 5110 A1 backplane supplies +5 V, +8.5 V, +12 V, −5 V, −12 V to the controller card among others — exact controller-only current draw not separately documented.
# '''Roberson 1976 ''Proceedings of the IEEE'' paper full text.''' Available only through paywalled IEEE Xplore or behind environment blocklists. Cited extensively for the 1.75 µs average microinstruction figure, but the wiki cannot independently verify against the original.
# '''Internal width of the control ROS / microcode store on the controller card.''' Wikipedia-talk-page claim of "256 × 32 bits" cannot be confirmed against SY31-0405-3, which describes the control ROS unit functionally without giving width. Treat as unverified.