Overclocking SuperFX

Post by **marshallh** » Sun Nov 27, 2005 7:56 pm

Ok, my idea is to overclock the SuperFX chip present in some 3d snes games (Starfox, Stunt race FX, Doom etc).

The game I have is Vortex which is alright but pretty choppy. It uses the second-revision FX chip, running at 21.4 MHz. (The first FX chip was just used in Starfox.)

Here's the game PCB.

And the SuperFX chip itself:

The ceramic resonator:

Back of the ceramic resonator where you can see the clock speed.

I plan on replacing the resonator with a 24mhz quartz crystal, with caps. Hopefully this won't have any adverse effects, and it MIGHT even run the game at a higher frame rate! I am inclined to think this, because the game still maintains the same time per frame, regardless of fps. (time based movement, not frame based.)

But what will most likely happen, is the game not booting. (The game is probably hardcoded to interface with the FX chip at certain timings.)

Wish me luck!

Houdini · Post by **Houdini** » Sun Nov 27, 2005 9:20 pm

I didnt understand a fragment of what you just said or posted............................................... but looks good!!!!????

timmeh87 · Post by **timmeh87** » Sun Nov 27, 2005 9:25 pm

i played starfox for snes the other day (for the first time

), and i noticed it was choppy sometimes. if it works im totally doing it. and faster than you :p

nos_slived · Post by **nos_slived** » Sun Nov 27, 2005 11:15 pm

Stick some rediculously high value oscilator, like 0.1GHz, and watch it fly! Of course, you'd probably fry the FX chip after the Nintendo logo...

vb_master · Post by **vb_master** » Mon Nov 28, 2005 8:57 am

If you're going to put it at .1GHz, please water cool it!

Foxx373 · Post by **Foxx373** » Mon Nov 28, 2005 10:24 am

It might not be that easy. The CPU clock needs to be caluclated by the bus speed multiplier. If the clock speed is a WEIRD number, then it might not boot. Ever wonder why computer CPUs are always like 200, 233, 266, 275, 300, 333, 366, 375MHZ? Its because of how the clock multipler works.

Bus MHZ x Multiplier = CPU Speed. This is how overclocking works. I dont know squat about the FX chip (i stopped caring, but back in the day i was into the thick of it) so try and get some tech info on it. The N64 can be overclocked just by adding jumpers. Some systems have simple jumpers that can modify the multiplier speed. This could be as simple as a swtich and a heatsink!

Also, you do know that the FX chip ties into the SNES CPU and replaces its Math Coprocessor? If you screw this up, you could fry the SNES.

The SuperFX chip is SUPPOSED to "overclock" the SNES to 10Mhz as well. No matter how fast you overclock the FX chip, the main CPU will still cause lag. You will need to overclock it as well.

timmeh87 · Post by **timmeh87** » Mon Nov 28, 2005 11:36 am

from what i know about microcontrollers, it dosent matter to the chip itself what clock speed you give it... yeah. like everyones saying - its a question of whether it will still be able to interact with other chips on the board.

i doubt that you would fry anything though. i just cant see how that would end up happening.

Post by **Sparkfist** » Mon Nov 28, 2005 11:51 am

Ok the type of chip the SNES uses for its main CPU doesnt have a heat sink and if its like the 68000 series it wont need one even if you overclock to twice its default speed. On top of that we've talked about overclocking other systems here. You can overclock the SNES all you want but be aware that if you push it too high you'll run into stablitiy issues as well as the audio falling out of sync with the video. I would suggest trying for a 50% increase right now.

Also the guys at http://www.epicgaming.us/ could help you with it, possibly.

Foxx373 · Post by **Foxx373** » Mon Nov 28, 2005 1:20 pm

Good luck, i hope it works out. Vortex really was an awsome game, even though it was choppy. I really like'd the music in that game. I remember back in highschool my friend asked me to take samples from it so he could use it for some of his remixing (or whatever the hell it was called).... and some other SNES games.

Post by **marshallh** » Mon Nov 28, 2005 3:16 pm

I'm going to swap out the resonator with a quartz crystal sometime later today. I wasn't really able to find any relevant information, except the SuperFX2 chip this game uses has 2 cores that run at 10.74MHz each, about half of 21.4mhz. Maybe a bus multiplier of 0.5x? Sounds odd.

Oh well, I'll be back soon with the results. If it works I'll be amazed and I'll be playing Vortex quite a bit more!

EDIT:
This game actually uses the standard GSU-1 chip, it's NOT the SuperFX2.

demonofaj · Post by **demonofaj** » Mon Nov 28, 2005 3:35 pm

What did the FX chip do to the SNES games? Google didn't really help me

MM007 · Post by **MM007** » Mon Nov 28, 2005 4:15 pm

Well, it enabled true 3-D for one, instead of the typical Mode 7. It was an upgrade for the video system, also containing an enhanced instruction set, I think. It draws more current than a standard cart though, and uses the extra pins on the edges of the SNES connector.

Post by **marshallh** » Mon Nov 28, 2005 10:26 pm

Foxx373 wrote: Also, you do know that the FX chip ties into the SNES CPU and replaces its Math Coprocessor? If you screw this up, you could fry the SNES.

Erm.. If I remember right the SNES didn't even have a FPU. Only integer arithmetic... Not even imul or idiv!

I guess you could forget fmul and fdiv as well then.

Anyway I've got the thing desoldered and since the resonator has caps built in, I'll have to put some 18pf caps tied to ground as well (to filter oscillator spikes)

I might be wrong about the SuperFX chip here being revision2. I saw some scans of the REAL verison 2 from Yoshi's island and it was in a PLCC, quad-smd package (more pins.)

Foxx373 · Post by **Foxx373** » Mon Nov 28, 2005 11:41 pm

Well, i havent done much in the whole SNES area in a LONG time, and from what i remember about the super fx was it had a bus that tied into the CPU, and the orignal math coprocessor was replaced during the game. i dunno, this was almost 10 years ago... Seriousally, i hope this all works out!

Post by **marshallh** » Tue Nov 29, 2005 3:48 pm

YEEEEEEEEAAAAAAAAAAAAAH! Vortex is now running at 24MHz! The mod was so simple it hurt!
Playing the game now was AWESOME. I got about 3-4 MORE FPS than at the previous speed.. The game ran at the same speed but much smoother. Wow!

I'm off to find a higher value crystal (maybe aroudn 26MHz would be optimal).

It was amazing playing Vortex again. In the spots with many enemies onscreen, the engine didn't even slow down!

I am amazed this worked! I'll get pictures of the mod up (it's extremely simple, just see what the resonator freq. was before.)

Foxx if you still have Vortex I definitely reccomend this mod! The game is a lot more playable now. (Not so danged hard)