PPU variants
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Beyond the well-studied 2C02G, we know of the following CPU revisions, both made by Ricoh and other manufacturers:
| RP2C02 | Suspected to exist, none found. Probably too buggy to be usable. |
| RP2C02A | differences unknown. Substantial timing differences attested relative to revision D |
| RP2C02B | " |
| RP2C02C | " |
| RP2C02D | differences unknown. |
| RP2C02E | OAMDATA is not readable. |
| RP2C02G | Writes to OAMADDR cause corruption of OAM. Leaving OAMADDR at a value of 8 or greater causes OAM corruption when rendering starts. |
| RP2C02H | no known differences relative to 2C02G. |
| RP2C03B | RGB PPU, believed standard. OAMDATA and PPU palette are not readable. Color emphasis bits set the corresponding channel to full brightness. |
| RC2C03B | Believed identical to 2C03B. |
| RC2C03C | " |
| RP2C03G | " |
| RP2C04-0001 | Scrambled palette and new colors, otherwise like 2C03. |
| RP2C04-0002 | " |
| RP2C04-0003 | " |
| RP2C04-0004 | " |
| RC2C05-01 | PPUCTRL and PPUMASK swap locations. Five LSBs of PPUSTATUS return a constant. Otherwise like 2C03. |
| RC2C05-02 | " |
| RC2C05-03 | " |
| RC2C05-04 | " |
| RP2A07 | PAL-B PPU. Vblanking is 71 scanlines long. OAM evaluation can never be fully disabled. Red/green color emphasis swapped. |
| RP2A07A | Some subtle differences in PPU that make this work better with Kevtris's HDNES, but otherwise believed identical to 2A07. |
| UA6528 | UMC-made clone of 2C02G. |
| UA6538 | UMC-made variant for playing NTSC games in PAL countries. Emits PAL-B video. Vblank IRQ intentionally emitted 50 scanlines later than 2C07. See also Clock rate. |
| TA-02N | ??-made clone of UA6528. |
| TA-02NP | ??-made clone of UA6538. |
If you know of other differences or other revisions, please add them!
