Skip to content

MON 033B (octal) - MALTN (AltPageTable)

Handles the MMU alternative page table (manual: MON 33B). The worker MALTN is carved in 003-S3CP and heads a small family of sibling entries (SKICK, SIDEN) that share a common body. All addresses/values are octal.

Status: byte-verified (dispatch chain + worker entry). The worker is real carved code in 003-S3CP.

CORRECTED 2026-07-13. Earlier versions of this folder used the disproven dispatch model (GOTAB as the monitor-call table, an "uncarved CALLPROC bridge") and named the worker ALTON. MON calls dispatch through MCTAB @ 005620B (segment 044-S3IDPIT), not GOTAB (which is MFELL for 224 of 256 calls). MCTAB[33B] = 037246B = MALTN, carved in 003-S3CP. See ../317B-ExecuteCommand/README.md and SINTRAN/CARVING-HANDOFF.md section 3a.

Dispatch path

flowchart LR
    A["User program<br/>MON 033B"] --> B["ENT14 level-14 entry<br/>026-S3IMPIT :072167B"]
    B --> C["GOTAB[033B] = MFELL<br/>MGOTA=071233B :071266B"]
    C --> D["MFELL level switch<br/>026-S3IMPIT :072114B -> CALLP 032201B"]
    D --> E["MCTAB[033B] = MALTN<br/>MCTAB=005620B :005653B = 037246B"]
    E --> F["MALTN worker<br/>003-S3CP :037246B"]
    class A blue
    class B,C,D,E teal
    class F green
    classDef blue fill:#E3F2FD,stroke:#0D47A1,color:#0D47A1
    classDef teal fill:#E0F7FA,stroke:#00838F,color:#00838F
    classDef green fill:#E8F5E9,stroke:#2E7D32,color:#2E7D32

Code location (dispatch path)

Byte offset = (addr - loadbase) in octal words x 2 (decimal). Every offset was reproduced with dd.

Role Segment Addr (octal) Byte offset Symbol Verdict
GOTAB[033B] slot 026-S3IMPIT.asm 071266B = 072114B 32108 -> MFELL VERIFIED
MFELL level switch 026-S3IMPIT.asm 072114B 32920 MFELL VERIFIED
MCTAB[033B] slot 044-S3IDPIT.asm 005653B = 037246B 1878 -> MALTN VERIFIED
MALTN worker body 003-S3CP.asm 037246B-037253B 7500 MALTN VERIFIED

Verify by hand (from tools/sintran-segment-carver/versions/L-VSX-500/segments/): 

dd if=026-S3IMPIT.bin bs=1 skip=32108 count=2 | od -An -tx1   ->  74 4c   (= 072114B = MFELL)
dd if=044-S3IDPIT.bin bs=1 skip=1878  count=2 | od -An -tx1   ->  3e a6   (= 037246B = MALTN)
dd if=003-S3CP.bin    bs=1 skip=7500  count=2 | od -An -tx1   ->  50 54   (= 050124B, MALTN entry word)

Instruction walkthrough

Full listing: 33B-AltPageTable.ASM.

Entry (037246B-037253B). 050124 LDT 124 loads a page-table selector, 042515 MIN ,X ,B 115 and 041105 MIN I 105 bump page-table bookkeeping fields, 051040 LDT I 40 / 023400 STD I ,B ,X 0 write a double word into a page-table slot (indirect indexed), and 047503 LDA I ,B ,X 103 reads back a status word. The sibling entries SKICK (037254B) and SIDEN (037256B) share the same page-table body.

Shared body (037272B+). 146146 RADD CLD SL DT / 010600 STT ,B -200 save the return link, then a normalize/count loop (037300B-037303B: AAA -12 / JAN / RADD AD1 0 DD / JMP -3), 120074 MPY 74 (index times entry-size 074) and 135075 JPL I 75 (helper @037404B) index and update a page-table entry. This is page-table (alternative-map) manipulation.

The exact page-table field semantics are inferred from structure; the entry, the sibling family and the loop/index arithmetic are byte-proven.

Parameter / register contract

Reg / field Dir Meaning Verdict
T (LDT 124) in page-table selector / bank VERIFIED (bytes); meaning inferred
,B -200 frame saved return link (STT ,B -200) VERIFIED (bytes)
,B -175,,B -177 frame staged operands (STT ,B -175, STA ,B -177) VERIFIED (bytes); meaning inferred
page-table slot in/out updated via STD I ,B ,X 0 and the MPY 74/JPL I 75 helper VERIFIED (bytes); layout inferred

Pseudo-code (for an emulator)

See 33B-AltPageTable.pseudo.c. The entry, the sibling family and the index/loop arithmetic are byte-verified; the alternative-page-table field layout is inferred.

Honest caveats

What is byte-proven: the full dispatch chain - GOTAB[033B] = MFELL, MFELL switches program level to CALLP, MCTAB[033B] = MALTN = 037246B, and the MALTN entry bytes at 037246B in 003-S3CP match the disassembly. MALTN/SKICK/SIDEN share one page-table body.

What is NOT proven: the exact alternative-page-table entry layout, the meaning of each staged field, and the internals of the 037404B helper. Those are inferred from structure, not these bytes.

Method: ../../../../../EXTRACTING-RESIDENT-CODE.md · master map: ../../MON-CALL-INDEX.md.