Guide 2 taken from the made-by-bacteria forums:
First you need to realize that there's three versions of the superfx chip. The mario chip (first version), the gsu 1 (second version) and the gsu 2 (final version). All three chips are fully backward and forward compatible with each other meaning you can install any superfx game rom onto any of these three chips and it will play. The mario chip is just a beta version of the gsu 1 so the mario chip and gsu basically run the same. Both the mario chip and the gsu 1 suffer a lot of slowdown when the game is trying to draw over a certain amount of objects. Really I think the only difference between the gsu 1 and the mario chip is that the gsu 1 can overclock faster but when the chip is constantly suffering from slowdown lag the overclocking barely makes any difference. The gsu 2 however is a huge improvement over the gsu 1 / mario chip. The gsu 2 has way less slowdown therefore overclocking the gsu 2 really boosts the overall framerate of any superfx game.
So what you need to do is find a suitable gsu 2 doner cart. Keep in mind that certain superfx games require a certain amount of ram to run. Really I think that doom is the best overall donor cart. Doom is fairly cheap, it's got a US lockout chip, it has a gsu 2, and it has the most ram ever put into a gsu 2 cart. The only thing that doom carts lack is the ability to save.
After you find yourself a doom cart the next part is tricky and frankly extremely annoying. You need to desolder the tiny surface mount maskrom chip from the doom pcb. Desoldering the surface mount maskrom is a royal pain and most of the time results in the cartridge becoming damaged causing it to no longer work. If you do manage to get the maskrom off safely then you need to wire up small wires to all the solder points of where the maskrom used to be. Again it's easy to damage something while soldering these wires onto the small fragile solder pads. Here's the superfx maskrom to standard eprom wiring chart:
Taken from this site:
If you manage to succeed with the wiring your cart should look something like this:
This picture's actually a gsu 1 pcb but the wiring mess would look pretty much the same. Once the wiring is finished if everything looks good then I suggest you epoxy the crap out of the solder pads and wires connected to where the eprom used to be. After your epoxy dries then you need to locate a rom of your favourite superfx game and burn it to an eprom. You should be careful though as me and doug discovered that there's a starfox 1 rom out there that actually kills a real superfx chip if you solder it into the cart. Once your eprom is burned you then solder it to those wires you attached using the above diagram to get the wiring right. If you managed to do this right the game will be able to turn on and run and play at normal speed.
Congradulations.....you're about.....2/3 of the way finished :bash:
The next part is the overclock. Each game has a different top speed it can overclock at without glitching or crashing. What I use to set the clock speed is just a half can or full can 4 pin crystal oscillator. You MUST use a 4 pin oscillator and not a 2 pin because the 4 pin produces a clock signal that the gsu 2 will accept but the 2 pin crystal won't. So you need to go on ebay or to your favourite electronics supplier and buy a range of crystal oscillator speeds. The default clock speed that all superfx chips are being fed is 21.4 mhz. I found that the fastest speed that all carts can run at is 28.3 mhz. But me and doug have built a number of carts that go faster than that. Our latest batch of starfox 1 carts (some were commissions and one became mine) are able to run at 42 mhz (probably even faster but I'm waiting on more oscillators to test this). Currently I have no clue why these three carts all run at 42 mhz but they all do. The first gsu 2 starfox 1 we built used an actual starfox 1 maskrom chip taken from a regular mario chip starfox 1 cart and soldered into the gsu 2 doom cart. However that cart freezes when you overclock it past 28.3 mhz. From all my research it seems that the rom in that maskrom is identical to the one that doug burned into the eproms on the carts that run at 42 mhz and beyond. So I guess using an eprom might help aid letting the cart run faster. The starfox 2 carts we produced we used the same eproms but they only can run at a top speed of 33 mhz, again I have no clue why.
Once you get your hand on 4 pin crystal oscillators at various speeds we're ready to perform the overclock modification. Don't worry about installing an oscillator that's too fast if the gsu 2 runs too fast the game will either glitch or crash but the gsu 2 is extremely resiliant and no damage will occur. I don't recommend wiring up an oscillator over 50 mhz as no game can run at that speed and I don't want to find out exactly how much punishment the gsu 2 can take before it melts or explodes.
A 4 pin crystal oscillator is a fairly simple device, inside of it is a crystal and a small circuit that makes it oscillate at the frequency marked on the oscillator. It's basically just a really small self contained clock circuit. There's four pins on crystal oscillators, one pin is power (vcc), another pin is ground, the third pin is clock signal out, and the fourth pin is unused. If you need to find the pinout of oscillators just google it they're all identical. Really all you need to do is wire up power and ground to the oscillator and then feed the clock output into the clock pin of the gsu 2. Crystal oscillators work on anything between 3.3v to 7v from the datasheets I read so the +5v in the superfx cartridge is just perfect for running your crystal oscillator.
To locate the clock pin on the gsu 2 chip just look at the pcb and find the clock circuit to the right of the gsu. The clock circuit is that little rectangular plastic ceramic resonator attached to a small hex inverter chip (should be marked as hcu04). That's the on board clock circuit that only has one thick trace connecting it to the gsu 2. You need to disconnect this thick clock signal trace using your favourite exacto knife or trace disconnecting tool. Then you need to solder a wire to the part of this trace that connects to the gsu 2, the other end of this wire connects to the crystal oscillator clock output pin. Then you need to find the snes cartridge pinout to figure out what pins are power (vcc) and ground. Just google the snes cartridge pinout it takes about 3 seconds if you know what you're doing. Then attach wires to the pcb for vcc and ground and wire them into your crystal oscillator to power it. And if you did everything correctly then you'll have the cartridge running at whatever speed your crystal oscillator is rated at.
It's very important that the gsu 2 clock input trace is completely disconnected from the on board clock circuit otherwise the overclock mod won't work. All you're doing is disconnecting the clock signal being fed into the gsu 2 and feeding it your own clock signal at your personal favourite speed.
Unfortunately both the mario chip and gsu 1 suffer from huge amounts of slowdown making it a complete waste of time to overclock either of these chips. Because the gsu 2 is the only chip that really improves when overclocked you're forced to solder games onto a gsu 2 pcb which is very frustrating and difficult.
.....As you can see this isn't exactly beginner s#it