REFORGE
Atari 2600 / F263
BEING VERIFIED

ABSOLUTE RMW FETCHES ADL/ADH BEFORE BOTH VALUE-BEARING WRITES

STATUS
BEING VERIFIED
AREA
Recompiler
RECORDED
2026-07-16
PUBLIC SOURCE
Research dossier / finding 263
RECORD ID
atari2600-f263
SNAPSHOT
f114355884d03a2c

MOS manual section 5.5 fixes absolute address formation as opcode, ADL and ADH reads before the effective memory transfer. Pinned Stella revision 90d01ecb309b9c3317ca762078d4df40681e111b supplies the remaining NMOS RMW sequence for ASL/ROL/LSR/ROR/DEC/INC and stable SLO/RLA/SRE/RRA/DCP/ISC: read the operand at ADH:ADL, write the old byte, compute, then write the modified byte.

Raw traces, ROM material, local paths, and personal data are not part of this public record.