CPU variants
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Beyond the well-studied 2A03G, we know of the following CPU revisions, both made by Ricoh and other manufacturers:
| RP2A03 | M2 duty cycle is 3/4 instead of 5/8. Lacks tonal noise mode. Has broken and disabled programmable interval timer on-die. Other differences? |
| RP2A03E | no known differences |
| RP2A03G | reference model |
| RP2A03H | no known differences |
| RP2A04 | Not actually a CPU at all, just a jumper in a 40-pin PDIP |
| RP2A07 | input clock divider is 16. Changes to noise, DPCM, frame timer tables. Fixed DPCM RDY address bus glitches. Other differences? |
| RP2A07A | no known differences relative to 2A07letterless |
| UA6527 | UMC-made clone of 2A03G. Has swapped pulse channel duty cycles. |
| UA6527P | UMC-made clone of 2A03G for compatibility with NTSC software in PAL countries. input clock divider is 15. Otherwise believed same as 6527P |
| UM6561 | NES-on-a-chip. CPU half believed identical to UA6527P. |
| TA-03N | ??-made clone of 2A03G |
| TA-03NP | ??-made clone of 2A03G for NTSC compatibility in PAL countries. Input clock divider is 15. |
| TA-03NP1 | ??-made clone of 2A03G for NTSC compatibility in PAL countries. Input clock divider is 15. Fixed DPCM problems? |
If you know of other differences or other revisions, please add them!
