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Macintosh ROM Version Numbers
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"Major Version of MacPlus ROM: $0075
Major Version of Performa 6400 ROM: $077D"

How to determine the ROM version of a Macintosh computer

ROMBase:                equ     $2AE            * base address of ROM
On early machines, ROMBase = $400000

 offset/length | description
  $00  |   4   | Checksum
  $08  |   2   | Major Version
  $12  |   2   | Minor Version
  $4C  |   2   | Sub-Release


  1. The ROM version does not necessarily reflect slight differences in ROM sets. For example, the Macintosh IIfx ROMs are slightly different from the Macintosh IIci ROMs, even though the ROM version number is the same.

  2. Macintosh Plus ROMs are also used in Macintosh 512K enhanced models.

  3. With the Centris 660AV and Quadra 840AV, a new 2 MB ROM was introduced.


ROM Version Numbers

Major VersionROM
$70FFMacintosh XL


MachineROM version
Macintosh 512Ke075
Macintosh Plus075
Macintosh SE276
Macintosh SE/30178
Macintosh Classic276
Macintosh Classic II67C
Macintosh Color Classic67C
Macintosh LC67C
Macintosh LC II67C
Macintosh LC III67C
Macintosh LC 52067C
Macintosh LC 55067C
Macintosh LC 57567C
Macintosh LC 47567C
Macintosh LC 58067C
Macintosh LC 63067C
Macintosh TV67C
Performa 20067C
Performa 400, 405, 410, 43067C
Performa 460, 466, 46767C
Performa 475, 47667C
Performa 550, 56067C
Performa 575, 578, 58067C
Performa 600, 600CD67C
Performa 630, 631, 635, 636, 637, 63867C
Performa 5200, 521577D
Performa 5260, 5300, 532077D
Performa 6110,6112,6115,6116,6117,611877D
Performa 6200,6205,6214,6216,6218,622077D
Performa 6230, 6290, 6300, 6310, 632077D
Performa 636077D
Performa 640077D
Macintosh II178
Macintosh IIx178
Macintosh IIcx178
Macintosh IIci67C
Macintosh IIsi67C
Macintosh IIfx67C
Macintosh Centris 61067C
Macintosh Centris 65067C
Macintosh Centris 660AV77D
Macintosh Quadra 60567C
Macintosh Quadra 61067C
Macintosh Quadra 63067C
Macintosh Quadra 65067C
Macintosh Quadra 660AV77D
Macintosh Quadra 70067C
Macintosh Quadra 80067C
Macintosh Quadra 840AV77D
Macintosh Quadra 90067C
Macintosh Quadra 95067C
Macintosh Portable378
PowerBook 10037A
PowerBook 14067C
PowerBook 14567C
PowerBook 145B67C
PowerBook 15067C
PowerBook 16067C
PowerBook 16567C
PowerBook 165c67C
PowerBook 17067C
PowerBook 18067C
PowerBook 180c67C
PowerBook 19077D
PowerBook Duo 21067C
PowerBook Duo 23067C
PowerBook Duo 25067C
PowerBook Duo 270c67C
PowerBook Duo 28067C
PowerBook Duo 280c67C
PowerBook Duo 230077D
PowerBook 52067C
PowerBook 520c67C
PowerBook 54067C
PowerBook 540c67C
PowerBook 530077D
Power Macintosh 4400/20077D
Power Macintosh 5200/75 LC77D
Power Macintosh 5300/100 LC77D
Power Macintosh 5260/10077D
Power Macintosh 5400/12077D
Power Macintosh 5500/22577D
Power Macintosh 6100 Series77D
Power Macintosh 6500/225, 6500/25077D
Power Macintosh 7100 Series77D
Power Macintosh 7200 Series77D
Power Macintosh 7300 Series77D
Power Macintosh 7500 Series77D
Power Macintosh 7600 Series77D
Power Macintosh 8100 Series77D
Power Macintosh 8500 Series77D
Power Macintosh 8600 Series77D
Power Macintosh 9500 Series77D
Power Macintosh 9600 Series77D

Checksum       |
byte #3        | ROM
@(ROMBase^+2)  |
    $EE        | 128K v1
    $F4        | 128K v2
    $EA        | 128K v3
    [other]    | 128K past v3

Checksum  | ROM
$4D1EEEE1 | Mac Plus ROM v1
          | ('Lonely Hearts')
$4D1EEAE1 | Mac Plus ROM v2
          | ('Lonely Heifers')
$4D1F8172 | Mac Plus ROM v3
          | ('Loud Harmonicas')