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Once of the things I've read was that the only reason the 32X's SH-2's didn't run at 28MHz was because the clock from the Genesis was multiplied 3x.

However, since we have half multipliers these days, or perhaps a 28MHz oscillator, could the 32X be overclocked?

Or would this render the 32X un-usable?

32X overclocking will happen as soon as me or Epicenter gets one. I don't expect much since the ROMs will probably be too slow for faster CPU(s).

TmEE co.(TM) wrote:32X overclocking will happen as soon as me or Epicenter gets one. I don't expect much since the ROMs will probably be too slow for faster CPU(s).

Well one game I see that could benefit is DooM. It slows down when your in an open area.

The way I see it, would be lifting the CLK pin on both, and tie them both to a 28MHz oscillator. I want to check first before doing such a thing.

From what people have said elsewhere on the boards, 32X DOOM's principle problem is poor division of labor - all the rendering is handled by one SH-2, while the other handles the sound mixing that the 68K could be doing. So I'm not sure overclocking would actually help that much, at least not nearly as much as a better DOOM engine port would.

Actually, I'd say the principle problem is lack of RAM. Doom 32X probably leaves the texture patches in the ROM since they won't all fit in RAM. That means that all drawing consists of fetching bytes from the cart. Worse, patches in Doom are arranged as columns, which doesn't fit the caches at all. Even worse, if they left the color maps in the ROM, you have a byte fetch of the data from the patch column followed by another byte fetch from the colormap, so TWO ROM fetches would be needed for every pixel drawn. Hopefully they put the color maps into SDRAM.

Oh yikes. A full DOOM colormap is 8.5 KB, so it's a good bet that's in the SDRAM, but yeah, the textures are far too huge to fit in the SDRAM, even for a single level. (Why, oh why could they not have outfitted the 32X with more RAM?)

So would this overclocking project speed up the 68K as well? If it does, then you could get some performance boost, but otherwise it wouldn't really make 32X DOOM run much faster.

As far as I know, overclocking the Genesis 68K causes the 32X to not be bootable.

The other way though I'm not sure of.

I'm not doing it until someone else does it first.

evildragon wrote:Once of the things I've read was that the only reason the 32X's SH-2's didn't run at 28MHz was because the clock from the Genesis was multiplied 3x.

However, since we have half multipliers these days, or perhaps a 28MHz oscillator, could the 32X be overclocked?

Or would this render the 32X un-usable?

The 32x uses an older tape-out of the SH2 which didn't run reliably at 28 Mhz (and has some interrupt bugs as well).

The 32x originally shipped with the FC3 version of the SH2, and the Saturn shipped with the FC4.

This is from memory, so it could be slightly wrong.

Toshi

I overclocked 32X recently... the increase was small (30MHz) but it seemed stable... and I didn't quite overclock just CPUs, all else too..... I'll look into it in more detail sometime.