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dingusppc/zdocs/developers/awacs.md
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AWACS is an audio controller present on several Old World Macs and can usually be located at IOBase (ex.: 0xF3000000 for Power Mac G3 Beige) + 0x14000.

New World Macs have a Screamer chip, which is backwards compatible with the AWACS chip, but with some additional capabilities.

Register Maps

NuBus Macs

Register Offset Length
Codec Control 0x0 3
Codec Status 0x4 3
Buffer Size 0x8 2
Phaser 0xA 4
Sound Control 0xE 2
DMA In 0x12 1
DMA Out 0x16 1

PCI Macs

All registers are 32-bit here.

Register Offset
Sound Control 0x0
Codec Control 0x10
Codec Status 0x20
Clipping Count 0x30
Byte Swapping 0x40

Separate volume controls exist for the CD drive and the microphone.

The DMA buffer size is set to be 0x40000 bytes, while the DMA hardware buffer size is set to be 0x2000 bytes.