ROM Checksums for TRS-80 Model 4

About This Page

Information from Tandy memos and technical bulletins were combined to form this list. Four 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
• Tandy preferred to provide two checksums for ROM A, which were checksums of the first 4K and the second 4K. Thanks to George Philips who figured it out, you can convert from a xxxx/yyyy checksum by adding the two together and dropping the extraneous 1 which appears before it (so, for example: BBC4/DA75 would be BBC4 + DA75, which is 19639. Drop the 1, and you get 9639).
• 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.
• If you have any ROMs which are shown as missing, please contact me.

Official Combinations:

Non-Gate Array (1st Generation Hardware).
This was set up to have 3 ROM chips – An 8K ROM A, 4K ROM B and 2K ROM C.

*: 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.

Gate Array (2nd Generation Hardware + Model 4D).
This was set up to have 2 8K ROM chips.

ROM A (8K In All Instances):

ROM B:

ROM C:

ROM D:

Gate Array Model 4s and Model 4Ds contain only two ROM chips, an 8K ROM A, and then a 8K ROM D which is just ROM B and ROM C in one ROM (with 2K wasted space). The actual code in the D ROM remains the same, only the ROM size has been changed:

ROM C/D by FRANK DURDA IV:

Character Generators:

German Keyboard:

ROMs which are not US/UK carry not only different character generators but different keyboards, making using them in an emulator somewhat difficult.

Thanks to Volker Kruckemeyer, this is the German keyboard

How to Get Your CRC’s

If you do not have a DOS system, you can type in this program and get your CRC’s. These programs were written by Dean Bear.

Longer Version (Runs Fast):

1 FOR I = 0 TO 38 : READ P : POKE 28656+I,P : NEXT I
2 DATA 17, 0, 0, 62, 16, 237, 71, 33, 0, 0
3 DATA 69, 26, 79, 9, 19, 237, 87, 186, 32, 247
4 DATA 24, 13, 58, 232, 55, 79, 168, 55, 63, 237
5 DATA 66, 55, 63, 237, 66, 195, 154, 10, 201
6 POKE 16526, 240 : POKE 16527, 111
7 DIM B(3): B(0)=0: B(1)=32: B(2)=48
8 DIM C(3): C(0)=32: C(1)=48: C(2)=56
9 PRINT "M3/M4 ROM CRCS FOR 3 CHIP SET"
10 FOR I = 0 TO 2
11 POKE 28658,B(I)
12 POKE 28660,C(I)
13 IF I = 2 THEN POKE 28677,0
14 D = USR(0)
15 IF D < 0 THEN D=D+65536
16 A$ = "ROM "+CHR$(65+I)+" = "
17 GOSUB 20
18 NEXT I
19 END
20 S=16:X=2
21 IF S<D THEN X=X+1:S=S*16:GOTO 21
22 PRINT A$;
23 T=D
24 FOR L=X TO 1 STEP -1
25 N=INT(T/S)
26 A=0
27 IF N>9 THEN A=1
28 IF L < 5 THEN PRINT CHR$(48+N+7*A);
29 T=T-N*S:S=S/16
30 NEXT L
31 PRINT
32 RETURN

Shorter Version (Runs MUCH Slower):

1 FOR I = 0 TO 8191 : D=D+PEEK(I) : NEXT
2 A$ = "ROM A = "
3 GOSUB 12 : D = 0
4 FOR I = 8192 TO 12287 : D=D+PEEK(I) :NEXT
5 A$ = "ROM B = "
6 GOSUB 12 : D =0
7 FOR I = 12288 TO 14335: D=D+PEEK(I) :NEXT
8 A$ = "ROM C = "
9 X = PEEK(14312): D = D - X - X
10 GOSUB 12
11 END
12 S=16 : X=2
13 IF S<D THEN X=X+1 : S=S*16 : GOTO 13
14 PRINT A$;
15 FOR L=X TO 1 STEP -1
16 N=INT(D/S)
17 A=0
18 IF N>9 THEN A=1
19 IF L < 5 THEN PRINT CHR$(48+N+7*A);
20 D=D-N*S : S=S/16
21 NEXT L
22 PRINT
23 RETURN

Quick Check for v1 vs v2

While not dispositive, George Phillips has identified quick way to see if you have v1 or v2 of the Model 4 ROM — via the CASS prompt!