I just want a Star Fox ROM that is pre-patched to run at 60fps.....or at least 30.
I heard folks can mod their carts to do it, but I have no idea what that entails, and wouldn't feel comfortable with it.
That involves taking a donor cartridge with a higher clocked SuperFX chip and burning the Starfox rom to an eeprom then soldering it to the board.
There appears to be some people here confused about slowdown vs render speed here. This is to eliminate slowdown. The reason slowdown occurs in retro games is because of the timing loop they operated on. Old games work on the principle that the television itself times how code can run. Code is split into three sections: Active scan code, HBlank code, and VBlank code. Think of them almost like entirely different programs.
In computing, the illusion of multitasking is achieved by switching between running code -- typically, a CPU can only run one program list's instructions at any given time. To make it look like multiple programs are running at the same time, they'll use an interrupt from the CPU to switch which program is being run. Every few microseconds, a CPU will switch to the next program to run. Since this happens so fast, we can't perceive the switch and it looks instantaneous.
Retro consoles kinda work like this, except it's the TV that determines the switch. This is because old TVs had a physical gun that would change the position of where the scanout was being drawn. When the gun stopped drawing and had to move to the next position, that provided perfect opportunities to run different kinds of code for different tasks not limited by BUS limitations due to scanout from the console.
I don't really need to explain the difference between active scan and hblank code here, but what's important is vblank code. Vblank is what happens when the gun reaches the bottom of the television screen and has to move all the way back to the top to begin drawing the next frame. This actually in relative terms takes a very long time, and during that time the entire console's resources are free to use. So Vblank is where most of the really heavy, long calculations go. However, since the television works at a fixed interval, if your VBlank code takes longer to execute, you'll run into problems.
When the raster gun moves back into position at the top of the screen to begin drawing the next frame, what happens is that the CPU of the system will switch back to a very small segment of code to check if VBlank is complete. When your Vblank code is done, you set a flag to indicate it's done, and if that flag isn't set, rather than switching back to the active scan segment of the code to begin drawing, the system will instead return back to the Vblank code to continue running. However, again, the TV determines timing, and thus you won't get another interrupt to switch back to active scan code until the gun moves back to the top of the screen, meaning an entire frame later.
Say our TV refreshes at 60 hz, but our VBlank code is longer than VBlank period. It thus takes 2 frames for us to finish our calculations. That means we technically refresh at 60/2 = 30 hz. If we took 3 frames, 60/3 = 20 hz. And so forth. Unlike a decoupled fixed timestep system like in Doom, old games typically have no real world way to tell how much time has passed between frames, so they don't account for the delay. So when this skipped beat occurs, to the player, it looks like they just actually started running slower, because now the internal logic is being done half as fast.
With emulation, we can actually redefine the parameters of the virtual television. What BSNES is doing is inserting extra scanlines into the "virtual television" to give segments of code more time to run. Thus, no more slowdown.
But, usually for superFX chip games, the framerate is also tied to how long it takes the math coprocessor to actually crunch the numbers for the vertexes, to build the tiles for the graphics, so forth. Thus, a game like starfox has two different timings to account for. This eliminates slowdown, but won't necessarily improve the framerate. Other emulators, and indeed switching Starfox Roms with a faster SuperFX cart, WILL change the starfox framerate by having the SuperFX math co-processor actually work faster. It takes less time for it to do the same math.
What people are seeing in the starfox videos is what starfox looks like with no slowdown, but not necessarily a free framerate.