U4
2MB EDO DRAM
RAM
Main memory
About this component
This is the CPU's 2 MB work RAM. Early boards use four 512 KB EDO chips; psdevwiki notes some PU-8 and PU-18 sub-revisions moved to a single RAM chip. Video RAM (1 MB) and sound RAM (512 KB) are separate chips next to the GPU and SPU. Hobbyists have expanded the main RAM by swapping in larger EDO chips, but games gain little from it.
What it does on this board
2MB system RAM + 1MB VRAM + 512KB sound RAM.
Pinout & readings
No pinout or reference readings yet — these show what each pin does and what a healthy part should measure.