TriMesh wrote:PU-7 and -1x PU-8s used the CXD8514Q
Everything from the -2x PU-8 to the early PSones used CXD8561[ABC]Q
The later PSOnes used another part that I can't remember the P/N for that had the SGRAM in the package.
I've not seen the CXD8514Q used with 2mb of vram, but anything with a CXD8561[ABC]Q should be fine.
It's possible there will be some compatibility issues though if you do upgrade, but then there are some issues with upgrading to 8mb as well.
Do you have a list of the other chips used on each motherboard (CPU/GPU/SPU/CD chips/bios etc) and what they were sold as (SCPH etc)?
I haven't really got a list, but I can tell you what I can remember:
PU-7, PU-8 up to and including -2x: CXD8530[AB]Q
Later PU8s, etc: CXD8606[AB}Q
PU-8, PU-18, PU-20: CXD2925Q
PU-22, PU-23, PSone: in CXD2938Q
CD Subsystem (DSP / Decoder)
PU-20: CXD1817R (both in one chip)
PU-22, PU-23, PSone: CXD2938Q (with SPU)
PU-7, -1x PU-8: CXD1923AR / CXA1645
-2x PU-18, PU-18: MC141685FT or TDA8771 / CXA1645
PU-20, PU-22, PU-23, PSone: BH7440AKV or equiv (There is a CXAxxxx Sony version)
PU-7, PU-8, PU-18 use separate CPU and GPU oscillators
PU-20, PU-22, PU-23, PSone use a clock PLL and a single xtal
There are some other parts that were used in the later PSones, but they were mostly moving RAM into other chips.