SNES info
Like the NES stats, this information is from rec.games.video.misc:
|Bits (CPU)| 16
|Bits (Gx) | 16
|CPU | 65c816
|APU (Aud) | SPC700
|MHz | 3.6
|Graphics | 256 x 224
| -2nd mode| 512 x 448
|Planes | 4
|Colors | 256/32768
|Sprites | 128
| - size | 32 x 32
|Audio | PCM 8-lyr
|RAM | 128K+64Kgx
The 65c816 is both hardware and software compatible with the 6502. All of the instructions in the NES are present in the SNES, and in the same locations.
The CPU ROM area is a confusing labyrinth that depends upon the game running at the time. Games are divded into two types: LoROM (Mode 20), which use 32K pages beginning at either $008000 or $808000, and HiROM (Mode 21), which use 64K pages beginning at either $400000 or $C00000. The choice of starting points depends on the further categorization of games into FastROM, which begin at either $808000 or $C00000 and run at 3.58MHz, and SlowROM, which begin at either $008000 or $400000 and run at 2.68MHz. Yeesh!
The matter of ROM mapping can be simplified by ignoring SlowROM games completely. Other than being located $800000 earlier, the mapping is the same. LoROM games, then, run from $808000 to $BFFFFF, filling only the upper 32K of each ROM bank. Thus, the game will fill $808000-$80FFFF, then move on to $818000-$81FFFF, etc. A15--that is, the 15th bit of the binary address--is always high for these games. HiROM games take all 64K at a time. The game will fill $C00000-$C0FFFF, then $C10000-$C1FFFF, etc. The game can run all the way from $C00000 to $FFFFFF. However, here SlowROM games diverge, running only from $400000 to $6FFFFF, as the $7's are reserved for RAM.
The SNES has more registers than the NES, but the accumulator and indices--A, X, and Y--are still the primary registers. When the system is turned on, all registers are 8 bits in length. The REP and SEP instructions can later expand the registers to 16 bits or shrink them again. As far as I know, A can be a different size than X and Y, but X and Y must the the same size.
