Assembly listing generated by yaYUL

Source Code

These source-code files are part of a reconstructed copy of Comanche 44, the initial release (though not the final mission release) of the Apollo 10 Command Module (CM) Apollo Guidance Computer (AGC) software. Subsequent releases were Comanche 45 and Comanche 45/2 (the flown release on Apollo 10). The reconstruction is believed to be exactly accurate, but in the absence of an actual Apollo-era listing of Comanche 44, some explanation of the reconstruction process is needed to insure confidence in that accuracy.

The starting point was the source code of Comanche 51 (separately previously reconstructed from an Apollo-era listing of Comanche 55, flown on Apollo 11). Comanche 51 source code was then modified by undoing changes known to have been made between revisions 44 and 51. The now-reconstructed Comanche 44 source code was verified by assembling it and checking that the assembled code had the expected known-correct memory-bank checksums. Note that page numbers in the reconstructed code match those on the Comanche 55 printout, although the source code would likely have different page numbers in a contemporary Comanche 44 listing.

Annotations that were not present in the contemporary source code have been added to the reconstructed code to justify each change relative to Comanche 51. Here's a guide to the Apollo documentation referenced in those annotations:

MIT/IL engineering drawing 2021153D, sheet 3. Listing of the memory-bank checksums for Comanche 44.
Comanche 55 (Apollo 11 CM final release) assembly listing.
Reconstructed Comanche 51 (Apollo 11 CM initial release) assembly listing.
Colossus 249 (Apollo 9 CM final release) assembly listing.
Guidance System Operations Plan for Colossus 3, Section 5, p. xiii. Table listing some Program Request Changes (PCRs) incorporated between Comanche 45/2 and Comanche 55.
Guidance System Operations Plan for Colossus 2E, Section 3, pp. ix-x. Tables listing some Program Change Requests (PCRs) incorporated between Comanche 44 and Comanche 55.
Programmed Guidance Equations for Colossus 2, Based on Comanche 55. Provides a pseudocode representation of portions of Comanche 55, showing change bars. The software revisions from which and to which the changes occurred are indicated by the markings next to the document page number:
- "Rev. 0" pages: change bars are from Colossus 249 to Comanche 45
- "Rev. 1" pages: change bars are from Comanche 45 to Comanche 45/2
- "Rev. 2" pages: change bars are from Comanche 45/2 to Comanche 55

In most cases, only the titles (rather than the full texts) of PCRs are known. In addition to the explanatory annotations, there is also a step-by-step commentary about the reconstruction process.

Comments expected to have been present in the original source code are prefixed with a single '#' symbol, whereas comments added later are prefixed by "##" or "###". Report any errors noted by creating an issue report at the Virtual AGC Project's GitHub repository.

051923,000002:                                                                                                  ## Copyright:   Public domain.
051924,000003:                                                                                                  ## Filename:    SINGLE_PRECISION_SUBROUTINES.agc
051925,000004:                                                                                                  ## Purpose:     A section of Comanche revision 044.
051926,000005:                                                                                                  ##              It is part of the reconstructed source code for the
051927,000006:                                                                                                  ##              original release of the flight software for the Command
051928,000007:                                                                                                  ##              Module's (CM) Apollo Guidance Computer (AGC) for Apollo 10.
051929,000008:                                                                                                  ##              The code has been recreated from a copy of Comanche 055. It
051930,000009:                                                                                                  ##              has been adapted such that the resulting bugger words
051931,000010:                                                                                                  ##              exactly match those specified for Comanche 44 in NASA drawing
051932,000011:                                                                                                  ##              2021153D, which gives relatively high confidence that the
051933,000012:                                                                                                  ##              reconstruction is correct.
051934,000013:                                                                                                  ## Assembler:   yaYUL
051935,000014:                                                                                                  ## Contact:     Ron Burkey <info@sandroid.org>.
051936,000015:                                                                                                  ## Website:     www.ibiblio.org/apollo/index.html
051937,000016:                                                                                                  ## Mod history: 2020-12-03 MAS  Created from Comanche 51.
051938,000017:

Page 1207

 051940,000019:    5074 051941,000020: 051942,000021: 051943,000022: 051944,000023:    5074 051945,000024: < < 051948,000027:    5076 051949,000028:    5077 051950,000029: 051951,000030:    5101 051952,000031:    5102 051953,000032:    5103 051954,000033:    5104 051955,000034:    5105 051956,000035:    5106 051957,000036:    5107 051958,000037:    5110 051959,000038:    5111 051960,000039:    5112 < 051976,000055:    5132 051977,000056:    5133 051978,000057: 051979,000058: 051980,000059: 051981,000060: 051982,000061: 051983,000062:

End of include-file

BLOCK 02 # SINGLE PRECISION SINE AND COSINE COUNT 02/INTER /a>051946,000025: 5074 65002 SPCOS AD HALF # ARGUMENTS SCALED AT PI /a>051947,000026: 5075 55075 SPSIN TS TEMK 15100 TCF SPT 41075 CS TEMK 5100 60000 SPT DOUBLE 55075 TS TEMK 15113 TCF POLLEY 57075 XCH TEMK 51075 INDEX TEMK 65000 AD LIMITS 40000 COM 61075 AD TEMK 55075 TS TEMK 15113 TCF POLLEY 15131 TCF ARG90 >051961,000040: 5113 00006 POLLEY EXTEND 71075 MP TEMK 55076 TS SQ 00006 EXTEND 75047 MP C5/2 67706 AD C3/2 00006 EXTEND 71076 MP SQ 67666 AD C1/2 00006 EXTEND 71075 MP TEMK 20001 DDOUBL 55075 TS TEMK 00002 TC Q /a>051975,000054: 5131 50000 ARG90 INDEX A 45000 CS LIMITS 00002 TC Q # RESULT SCALED AT 1 # SPROOT WAS DELETED IN REV 51 OF MASTER. ASS. CONT. HAS CARDS. SINGLE_PRECISION_SUBROUTINES.agc. Parent file is MAIN.agc