I'll start by saying that the blue "Debugging Station" Playstations have 2Mb (Mebibytes or "megabytes") of work RAM! The standard amount! Today I compared every RAM part between the SCPH-1001, DTL-H1001 and DTL-H1101 and found:
IC106-9 are the same on all boards (likely WRAM)
IC201 and 2 on the DTL are 256K x 16. The corresponding DRAM on the SCPH is in a single 128K x 32 chip (likely VRAM)
The other RAM, IC310 on both boards is 256K x 16.
Unless any PSX techies know otherwise (that the "other 2Mb" is embedded in the CPU) know this as the truth!