User:Tepples/Super NES vs. Genesis

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The WDC 65816 CPU in the Super NES is indeed slower than the Motorola 68000 CPU in the Sega Genesis (called Mega Drive outside North America) at some tasks. This doesn't mean the system as a whole is slower or otherwise inferior to the Genesis, though some advantages of the Super NES hardware aren't necessarily showstoppers either.

Color and resolution

The 5-bit-per-channel video DAC in the Super NES makes sky gradients less bandy than on Genesis. (Need counterpoint)

Super NES S-PPU has color math, which allows for mist or shadow with less hard edges than shadow/highlight mode of the Genesis VDP. Though the Genesis's H40 mode makes pixels of striped or checkerboard layers small enough that typical TVs of the time would blend them, it still doesn't accomplish subtle mood lighting quite as smoothly as color math.

Some Super Famicom RPGs use its 512-pixel-wide hires mode for sharper text. This allows 21x14-pixel kanji glyphs (on a 24x16-pixel grid) in the space where a Mega Drive RPG in H40 mode would show 14x14 (on a 16x16-pixel grid). But given the typical capabilities of TVs of the time, 14x14 is already legible enough up to the composite video bandwidth limit.

Raster effects

Both the Super NES and the Genesis can horizontally scroll individual scanlines of a background plane for parallax. The Super NES uses a memory controller feature called horizontal blank direct memory access (HDMA) to poke the PPU in the background each scanline, whereas the Genesis uses a table of scroll positions in VRAM. The difference arises with any raster effect other than horizontal scrolling. Axelay stretches the background plane by an amount that increases down the screen for a "rolling log" effect. It does this by varying the scrolling Y coordinate with HDMA. The special stage in Sonic 3D Blast for Genesis shows the same effect, but the CPU has to stop and poke the vertical scroll between each scanline and the next.

Super NES has mode 7, a scanline rotozoomer that allows for behind-the-car racing games with a floor plane taking two-thirds of the screen. On the other hand, a 68K without the SVP can draw a height-mapped (or "voxel") landscape faster than a 65816 without the SA1 or GSU coprocessor.


Super NES has a hardware sampler on a dedicated memory bus. This lets it mix up to eight sampled waves compressed with ADPCM-like Bit Rate Reduction (or a couple forms of noise) without a hiccup. Genesis audio, by contrast, is often scratchy as hell due to video DMA blocking the Z80, and mixing even two uncompressed PCM samples on the Z80 was seen as an accomplishment. One workaround is to use the FM voices wisely. Using PSG's tones and noise for percussion or for an accompaniment line frees up FM channels. On the other hand, there's a lot more learning curve in creating patches for Yamaha OPN FM than for a sampler.

To increase polyphony on OPN, use algorithm 4. All channels can play just-tuned dyads of two 2-op voices, much as a sampler can play chord samples. Channel 3 has a special mode to set the four operators' frequencies independently to play two independent notes.

OPN and PSG produce overall brighter timbres than the S-DSP, which applies a Gaussian interpolation that tends to muffle high frequencies. OPN also allows the modulator to decay over the course of each note, which produces a timbre that becomes gradually less bright. Approximating this on a sampler requires fairly large samples unless the driver sacrifices a voice to use the S-DSP's rarely used 2-operator FM mode, and a lot of games just end up storing a small amount of decay and looping the last period of the wave assuming that other voices will mask the difference.

S-DSP lets the driver reserve a block of memory (usually on the order of 8 KiB) to capture the output and feed it back for echo. This can free up a voice or two compared to 2-channel echo techniques.

Backward compatibility

Power Base Converter vs. Super Game Boy...


The original Genesis controller is inspired by control panels of arcade games of the time: three action buttons and a button to start a game after having inserted a coin. This matches the input section of the original JAMMA harness pinout.

Super NES comes with a controller with six action buttons: four face buttons and two shoulder buttons. Genesis eventually got a controller with six face buttons, corresponding to the "kick harness" extension of later fighting games. Genesis games have to be usable with the original 3-button controller, such as mapping the other three buttons' actions to the sometimes awkward chord of Start+A, Start+B, and Start+C.