About This Page

Information from Tandy memos and technical bulletins were combined to form this list. Two things to note:

  • Analyzing the ROMs and researching for possible mistakes took a lot of the TRS-80 community out there, and I thank them all. Special thanks to George Philips and Ken Brookner for tackling the hardest issue of them … ROM A Checksum 1591
  • ROM C uses locations $37E8 and $37E9 as a pass-through for printer information. PEEKing a ROM to dump it will not work unless the printer is off because those 2 locations will contain whatever data they contain otherwise. When MEMTEST does its CRC checks, it skips those 2 locations. Thanks also to George Philips for that info.

Official Combinations:

 
Description
ROM A
ROM B
ROM C
 
Level I
BBC4
DA75
407C
 
Level II
9639
407C
2B91
 
Level II
9639
407C
2B91
 
Level II
9639
407C
2B91
 
Network III
9639
407C
2764
 
Network III
9639
407C
676A
 
Network III
9639
407C
276A
 
Intermediate US (60Hz) *
9639
407C
1591
 
Intermediate English (50Hz)
9610
407C
1591
*
Both the Model III and Model 4 list 9639 407C 1591 as a valid ROM combination, which is somewhat baffling. That combination will run on both a Model III and a Model 4. It contains some code calling the Model 4 CRTC which runs fine on a Model 4 and is ignored on a Model III.

ROM A:

Checksum
Part No.
Description
BBC4
_______
This is ROM A for every Model III Level I
9639
8041364
This is ROM A for every Model III Level II

ROM B:

Checksum
Part No.
Description
DA75
_______
This is ROM B for every Model III Level I
407C
8040332
This is ROM B for every Model III Level II

ROM C:

Checksum
Part No.
Description
Status
407C
8040332
This is ROM C for every Model III Level I
1591
8040316
v1 – First released version. U.S. Version (60Hz). Did not allow control codes to be entered from the keyboard although those codes were documented in the owners manual.
MISSING
2EF8
8040316B
v2 – Rom C, Rev B – 1980. Corrects problem with control codes. Changes screen print from SP to SHIFTDOWN ARROW*
2F84
8040316C / AMX-4642
v3 – Rom C, Rev C – 1981. Corrects “garbage on screen” power up problem discussed in Technical Bulletin III:10. The differences between v2 and v3 are very small. First, a byte in the printer character lookup table which was wrong in both v1 and v2 has been fixed (3185H had 40H where it should have been 60H). Second, the instruction at 3468 (FDC Bootup routine) previously had a CALL (17 cycles) to a routine containing PUSH BC (11 cycles), POP BC (10 cycles), NOP (4 cycles), and RET (10 cycles) to stall for processing of the OUT command which preceded it. This was changed to PUSH BC (11 cycles), POP BC (10 cycles), NOP (4 cycles), which reduced the stall by 27 clock cycles.
____
AXX-7078
v4 – This is the Network III ROM C used for Network III Student Stations. This part is found ONLY in the 26-1059 Model III Student Station, or Network III Student Station upgrade kits.
MISSING
2B91
________
Model III Level II
2764
________
Network III ROM
MISSING
676A
________
Network III ROM
MISSING
276A
________
Network III ROM
MISSING
158C
8049006
English Version (50Hz)
MISSING
1E04
________
German

Character Generator:

Checksum
Part No.
Description
Status
19B9
8044316A
For U.S. and Kana