SNES CPU and PPU revisions?

How many different revisions of the CPU and PPU chips were there?
I have 4 (broken) motherboards here (3 PAL and 1 NTSC). 2 have S-CPU A and 2 have S-CPU B, one of the PAL boards has a S-PPU2 C and the other 3 have S-PPU2 B.
Is there an S-PPU2 A?

 

Yup, there are at least 4 versions of S-PPU2:
"S-PPU2", "S-PPU2 A", "S-PPU2 B", and "S-PPU2 C"

As for CPUs, there are only S-CPU, CPU-A, and CPU-B.