Overclocking SuperFX

[Player0]

The SuperFX chip is different in most of the carts. There are several different minor revisions in the few carts I have recently opened up. Primarily, there is Mario Chip, GSU-1, GSU-2, with GSU-1 being most common. However, it also has many sub revisions.

StarFox itself uses the glop top Mario Chip in earlier versions, later versions report it to use GSU-1. StarFox doesn't have a clock-gen on it (usually), which means it gets its clock from the SNES itself. 21Mhz according to most things I've read.

Actually, the clock pins super easy to identify with the GSU-1 models, and maybe with the gloptop. The GSU-1 accepts a master 21Mhz signal from the SNES, and a second 10/21/whatever Mhz clock for it's internal purposes. Overclocking StarFox with a GSU-1 would take a matter of 5 minutes. Just create a simple astable oscillator at whatever frequency you'd like to try and connect it to the internal clock pin.

I just built the StarFox2 cart from SNESdev (pics at http://www.liquidninjas.com/bbs/showthread.php?t=13388, sorry if cross site linking is not allowed). It works great, but as my posts suggest, slowly

There are probably people who know a lot more than me about this SFX chip situation. The emulator crowd. Information is very sparse tho in public circles. On Stunt Race FX, the internal clock is given from that 21Mhz crystal, and I am almost convinced that the clock generating circuit is splitting that in half to 10.7mhz. There are two Inverters in use on hex inverter chip on the clock gen sections of these carts. Each pulse from the xtal at 21mhz is flip-flopping the inverters, so im sort of thinking that the pulse outputted is 10.7.

Whether the SuperFX has a clock splitter built in I cant confirm. The patents never mention it, but most emu docs/people suggest it. Why generate a 10.7Mhz clock on the cart then?

When I get my new ceramic xtals in, Im going to try a 40-42Mhz xtal on the clock gen of Stunt Race FX which I suspect to be v1.0 (SFX chip 9409). I beleive my other Stunt Race FX cart which I broke is v1.1 (SFX chip 9416). Im assuming that if the clock generator, or the SFX itself, splits the clock, then a 40mhz pulse should put me at 21Mhz, which may work on the superFX chip if the specs are right.

Or, SuperFX just isnt stable at 21mhz. I dont really know, its all assumptions and I really need to test.

[Player0]

PS - If anyone knows better than me and Im wrong, please let me know! I just want to know how all this works and all I can do is guestimate at this point

Also, in terms of StarFox itself, I built my cart with a ROM socket so as soon as I order a couple more 27C801-120s and overclock my cart, I should try the original StarFox image in there

[MM007]

A flip-flop does not just make the clock devide in half, but also makes the square wave pulses equidistant. I use this fact in several applications. Perhaps some games need equidistant Highs and Lows for some reason?

[Player0]

Equidistant square waves should be a necessity of a clock gen running at a particular frequency. If the lows werent equidistant, the frequency would be different

But can you confirm that a flipflop taking a clock pulse from a crystal is going to divide that original clock pulse in half?

So with a 21.4mhz crystal pumped in to a flip flop, youre going to get a 10.7mhz clock out right?

[Player0]

I tried hooking the clock pin of the SFX to pin 1 from the SNES which should be a 21mhz clock. The cartridge booted up but the game didnt play the least bit faster, even though I beleive I doubled the clock rate.

The cart wont boot with the pin completely disabled. Actually, after the tiniest bit of flexing, my pin fell right off unfortunately. Probably not something I can fix. Ill need to start over completely, so just something to be aware of

[MM007]

I was refering to the HIGHs and LOWs being equidistant to EACH OTHER.

And yes, it will divide the frequency in two by its very nature. It is basically a latch that activates or deactivates every time it detects a HIGH pulse. The frequency halving aspect is what makes it possible for it to be used to make binary counters and temporarily store binary values, like in the NES and SNES controllers.

[King of Bling]

What I've heared is that the instruction set is the same for all Super FX chips, so in answer to the problem of being unable to overclock Star Fox, why not run it on a Doom cartridge? Player0, have you had any progress yet?

Also what is the difference between the Stunt Race FX 1.0 and 1.1 carts? Their Super FX chips are labelled as GSU-1 and GSU-2-SP1 respectively, but does that mean that my 1.0 version would be any worse if I used it for Star Fox 2?

[Jongamer]

BUmp

[Kenny_McCormic]

i overclocked my doom cart to 49 mhz and added a 40 mm fan there was a slight improvement in framerate and the framerate never went down no matter what because just like the pc version doom has a capped fps and the cap on the snes port is rather low
so i have a new plan turn it into a dev cart what kind of rom does the doom cart use? is it reprogramable? where can i find software for burning the snes rom files to the cart?

[Jongamer]

YEEEEEEEEAAAAAAAAAAAAAH! Vortex is now running at 24MHz! The mod was so simple it hurt!

Hey marshallh!
I just wanted to say that I did your mod today (on Vortex), and it works great!

PS:The game did not boot when I used the two 18pF caps, but it works great without the caps.

ConsoleFun

So I guess you dont need caps at all, sweet no I dont have to bother looking for them.

[Drakon]

Sorry for the massive bump but I've made a few discoveries regarding this overclock.

I really wanted to overclock starfox 1 since that's one of my favourite games. Me and a friend collected/built 3 different versions of the game. The first version is the original mario chip based cartridge. The second version is a super fx 1 based cartridge where we converted a stunt race fx to starfox 1. And the third version is a superfx 2 based cartridge where we converted doom to starfox 1.

Naturally the first thing I tried to do was the standard stunt race fx overclock where you remove the ceramic resonator from the pcb and install a 2 pin crystal in its place. When I did this mod starfox 1 would either run slower than the original speed (underclocked) or at around the original speed. I even stuck a 200 mhz 2 pin crystal in and the game still ran at just the original speed.

I found a post here:

http://www.sega-16.com/forum/showthread ... erclocking

This guy overclocked his mario chip based starfox 1. Instead of using a 2 pin crystal he used a 4 pin crystal oscillator. However since the mario chip is garbage he only got it going at 25 mhz with a lot of heatsinks otherwise the cartridge would overheat.

I decided to look at my 3 different types of starfox 1 cartridges and see the differences in the clock circuits. The first thing I noticed was that all 3 different super fx chips (mario, super fx 1, super fx 2) used the same pins to get the clock signal. In fact it looks like all three chips share the exact same pinout. The difference between the mario chip and the later chips is that the mario chip is fed a raw 21.5 mhz clock signal with no parts between it. For some reason the later chips are fed 21.5 mhz passed through a hex inverter. I figured since the mario chip is having the clock signal fed directly to it that perhaps starfox 1 is programmed to have that type of a clock signal.

I disconnected the super fx 2 clock pin trace from the entire clock circuit on the pcb. Then I wired up a 25 mhz 4 pin oscillator directly into the chip. And BAM, the game was finally overclocked and running great. I also tried different clock speeds. 32 mhz on the superfx 1 causes the game to freeze in the intro. 32 mhz on the superfx 2 causes the game to freeze at the end of the first stage. 30 mhz on the superfx 2 is fine for route 1 (I cleared the entire game on route 1 at 30 mhz) but on route 2 the game randomly froze on stage 2. 27 mhz so far everything is fine on the superfx 2. I cleared all of route 1 and 2 at 27 mhz and today I'm testing route 3, the hidden stages, and training mode.

Whenever the game froze the super fx 2 chip wasn't even warm so I think it was just running too fast for the programming I doubt it was overheating.

[Drakon]

testing done....video made....

http://www.youtube.com/watch?v=tOU2GikR ... ideo_title

[jtsuprastar92]

hey folks. i was reffered to this forum by racketboy. i have a yoshis island and is has a broken crystal thing. i have been reading this forum and am wondering if someone would be willibng to help me out my soldering the things needed to get it back up and running these are the pics for the cart. also the battery clip thingy was bouncing around inside the cart when i opened it. its probably what broke it in the first place
http://i1250.photobucket.com/albums/hh5" onclick="window.open(this.href);return false; ... 1229-1.jpg

http://i1250.photobucket.com/albums/hh5" onclick="window.open(this.href);return false; ... CF1232.jpg