← Home · Hardware
AGA Chipset — A1200 / A4000 / CD32
Overview
The Advanced Graphics Architecture (AGA) is the final custom chipset developed by Commodore, shipping from 1992. It dramatically expands colour depth, palette size, sprite capabilities, and blitter bandwidth while retaining full OCS/ECS backward compatibility.
Chip Summary
| Chip |
Name |
Changes from ECS |
| Alice |
MOS 8374 |
Super Agnus successor: 64-bit bus, FMODE register |
| Lisa |
(unnamed MOS) |
ECS Denise successor: 8-bit palette, 256 colours |
| Paula |
MOS 8364 |
Unchanged from OCS/ECS |
Contents
AGA vs ECS — Key Differences
| Feature |
ECS |
AGA |
| Colour registers |
32 (12-bit) |
256 (24-bit) |
| Max simultaneous colours |
64 EHB / HAM |
256 (or HAM8: 262,144) |
| Blitter bus |
16-bit |
64-bit (FMODE) |
| Sprite width |
16 px |
64 px |
| Sprite colours |
3+transparent |
15+transparent (64-colour attached) |
| Bitplane depth |
6 planes max |
8 planes |
| Palette select |
1 bank |
4 bitplane banks, 4 sprite banks |
Identifying AGA at Runtime
#include <graphics/gfxbase.h>
extern struct GfxBase *GfxBase;
BOOL is_aga = (GfxBase->ChipRevBits0 & (1 << GFXB_AA_ALICE)) != 0;
| ChipRevBits0 bit |
Flag |
Meaning |
| 4 |
GFXB_AA_ALICE |
AGA Alice present |
| 5 |
GFXB_AA_LISA |
AGA Lisa present |
AGA Machines
| Model |
CPU |
Notes |
| A1200 |
68020 14 MHz |
Budget AGA; Gayle IDE; PCMCIA; 2 MB Chip |
| A4000 |
68030/040 25 MHz |
High-end; Zorro III; IDE; 2 MB Chip + Fast |
| A4000T |
68040/060 |
Tower variant; SCSI |
| CD32 |
68020 14 MHz |
Game console; CD-ROM; SX-1 expansion |
References
- ADCD 2.1 Hardware Manual — AGA chapters
- NDK39:
graphics/gfxbase.h, hardware/custom.h
- Commodore A1200/A4000 Technical Reference Manuals (local archive)
fca930d0db