This is a (nonexhaustive) list of write-twice registers:
| Addr | name |
|---|---|
| 2104h | OAMDATA |
| 210Dh | BG1HOFS |
| 210Eh | BG1VOFS |
| 210Fh | BG2HOFS |
| 2110h | BG2VOFS |
| 2111h | BG3HOFS |
| 2112h | BG4HOFS |
| 2113h | BG4HOFS |
| 2114h | BG4VOFS |
| 211Bh | M7A |
| 211Ch | M7B |
| 211Dh | M7C |
| 211Eh | M7D |
| 211Fh | M7X |
| 2120h | M7Y |
| 2122h | CGDATA |
This is a (nonexhaustive) list of read-twice registers:
| Addr | name |
|---|---|
| 2138h | RDOAM |
| 213Bh | RDCGRAM |
| 213Ch | OPHCT |
| 213Dh | OPVCT |
Source: http://problemkaputt.de/fullsnes.htm