U3
CXD2925Q
Sound
Sound processing unit
About this component
The SPU mixes up to 24 ADPCM sample voices and the CD audio stream, then sends the result to the audio DAC. It has its own 512 KB DRAM for samples and reverb workspace. On later boards Sony merged it into the CD controller chip, so a 'no audio' fault on a PU-22 or later may trace back to that combined part rather than a separate SPU. Part variants: CXD2925Q is documented on PU-8. From PU-22 the SPU is merged with the CD DSP/decoder as CXD2938Q; on the PSone PM-41 it is CXD2941R with sound RAM built in. PU-7 part not confirmed.
What it does on this board
24-channel ADPCM audio.
Pinout & readings
No pinout or reference readings yet — these show what each pin does and what a healthy part should measure.