A78
A78 Header Editor
Atari 7800 ROM Header Tool · v3 / v4.2 spec
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⚙ Header Version & Identity
core
▼
Header Version
byte 0
Version 3 (legacy)
Version 4 (current)
v4 includes mapper/audio/irq fields (bytes 64-69)
ROM Size
bytes 49-52
Auto-detect from file
8 KB ($2000)
16 KB ($4000)
32 KB ($8000)
48 KB ($C000)
64 KB ($10000)
128 KB ($20000)
256 KB ($40000)
512 KB ($80000)
1 MB ($100000)
Game Title
bytes 17-48, max 32 chars
📋 Cartridge Type (v3 compat)
v3
▼
Deprecated in v4 but recommended for backward compatibility. Set to $FF,$FF if v4-only.
Type A
byte 53
Type B
byte 54
🎮 Controllers
core
▼
Controller 1
byte 55
Controller 2
byte 56
📺 TV Type & Save Peripheral
core
▼
TV Type
byte 57
Save Peripheral
byte 58
⚡ IRQ Source & Passthrough
v3
▼
External IRQ
byte 62
Slot Passthrough
byte 63
📌 Mapper (v4)
v4
▼
Mapper
byte 64
0 - Linear
1 - SuperGame
2 - Activision
3 - Absolute
4 - Souper
Mapper Options
byte 65
Bankset ROM (bit 7)
Bankset
Option @$4000 (bits 0-2)
0 - None
1 - 16K EXRAM
2 - 8K EXRAM/A8
3 - 32K EXRAM/M2
4 - 16K EXROM (SG only)
5 - EXFIX (SG only)
6 - 32K EXRAM/X2 (SG only)
🎵 Audio (v4)
v4
▼
Hi/Lo channel pair, bytes 66-67. Same bit layout for both.
Audio Hi
byte 66
ADPCM @$420
Covox @$430
YM2151 @$460
POKEY config (bits 0-2)
0 - None
1 - POKEY @$440
2 - POKEY @$450
3 - Dual POKEY @$440+$450
4 - POKEY @$800
5 - POKEY @$4000
Audio Lo
byte 67
ADPCM @$420
Covox @$430
YM2151 @$460
POKEY config (bits 0-2)
0 - None
1 - POKEY @$440
2 - POKEY @$450
3 - Dual POKEY @$440+$450
4 - POKEY @$800
5 - POKEY @$4000
⚡ Interrupt (v4)
v4
▼
Interrupt Hi
byte 68
Interrupt Lo
byte 69
🔎 Header Hex Preview (128 bytes)
▼
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