Alice is the successor to Super Agnus and is the DMA controller and Copper/Blitter engine for AGA machines.
### Key Enhancements over Super Agnus
**64-bit DMA fetch bus (FMODE):**
Alice can fetch 2 or 4 words per DMA cycle via the `FMODE` register ($DFF1FC). This dramatically increases the bandwidth available to the blitter and bitplane DMA.
**Extended bitplane depth:**
Alice supports up to **8 bitplanes** (256 colours), compared to OCS/ECS's 6-plane limit.
**BPLCON4:**
Alice adds `BPLCON4` to control bitplane bank selection — which 64-entry block of the 256-entry colour table is used by the bitplanes.
### ALICE_ID
Alice can be identified via `VPOSR`:
```asm
move.w $DFF004, d0 ; VPOSR
lsr.w #8, d0
```
| VPOSR[15:8] | Chip |
|---|---|
| $22 | Alice AGA (standard) |
| $23 | Alice AGA (some A4000 revisions) |
---
## Lisa (AGA Denise)
Lisa is the display chip successor to ECS Denise, providing 8-bit colour output (256 colour registers) and extended sprite capabilities.
### Key Enhancements over ECS Denise
**256 colour registers:**
Lisa provides COLOR00–COLOR255, each 24-bit (32-bit register with low byte unused).
**4 colour banks for bitplanes:**
`BPLCON4` selects which 64-register bank (0–3) the bitplanes use for lookup. This allows dual-playfield each using a different 64-colour palette.
**Sprite bank selection:**
`BPLCON3` bits select which colour bank sprite pairs use.
**Extended sprite width:**
Sprites can be 16 or 64 pixels wide in AGA mode.
**Lisa ID:**
Readable from `$DFF07C` (DENISEID):
```asm
move.w $DFF07C, d0 ; DENISEID = $00F8 for AGA Lisa
```
---
## FMODE — DMA Fetch Width Register ($DFF1FC)
The most critical AGA-specific register. Controls the data bus width for blitter and bitplane DMA:
> Writing FMODE on OCS/ECS machines writes to the `LISAID` location (read-only) — no hardware damage, but the read-back value is incorrect. Always verify AGA presence before writing FMODE.
