Winbond W56964

A datasheet is available in a Purdue University project report. It is a bit discouraging that they apparently didn't get it to work.

There used to be application notes in Google's cache. That page also had what Winbond calls middleware, i.e., the driver.

Sunplus SPMA100B

No datasheet available and registers are different although the chip is pin-compatible to the above. Traces generated with the original firmware and register dumps during operation suggest:

#define SPMA_SEQUENCER_FIFO    0xc5
#define SPMA_SEQUENCER_SPACE    0xc7    // decreases with every written byte

#define SPMA_SEQ_FIFO_EMPTY    0x80
#define SPMA_SEQ_FINISHED    0x40
#define SPMA_SEQ_FAILED        0x20

Power controls. No sound or clicks if sequence (0xff -> 0x7e -> 0x1e -> 0x04 -> 0x00) is wrong.

0xe3 ... 0xe6
Volume registers where 0=Mute, 1=-30dB ... 31=0dB in 1dB steps (equal to W56964)

Macronix MX92U832AZCG

Seems to be a product of Modiotek. No further information available.

OKI ML2864

The datasheet explains the concepts a bit more detailed. The Exclusive Format might solve the mystery of the data send to the SPMA100B.