Questions about making a Star Fox 2 cartridge in a post-SNESMini era.

There are a number of NES games that add RAM inside the cartridge for general use and not for saving data as well. Also Static RAM is not always intended for use with a battery. Modern computers use DRAM (Dynamic) because you can get much larger density for less cost. But the trade off is you must refresh the memory cells over time or you will lose the data. With Static RAM this is not an issue. All that matters with SRAM is that power is maintained above the threshold noted in the datasheet.

It is possible to hack apart a Super FX cartridge and wire a socket but you'll have to be very careful to make sure it doesn't fall apart on you. It's not a bad idea to do what you said and make a test cart. But I question how useful that would even be. There are very few Super FX games. Unless you are planning to program something for the Super FX there are only 2 games you might want to play using EPROMs. Star Fox Competition and Star Fox 2. Doesn't seem to me like you'd need a test cart. Plus you can always just dump your EPROM with your programmer after you program it.

You mentioned you didn't realize it wasn't a DIP ROM chip. If you aren't used to soldering surface mount stuff and more importantly desoldering then you might consider having someone else build you a cartridge. When I tried to do it many years ago with only some experience mainly with DIP chips I lifted traces off the board and ended up not succeeding. If you don't have really nice equipment and the experience I think it's fairly likely you might also have the same result. And back when I tried the games were much cheaper. I used a Doom cartridge that cost maybe $5 at most.

 

DRAM has been common since the 1980's. The VIC20 used SRAM, the C64 used DRAM. The refreshing is not the major hassle though. SRAM can sit directly on a cpu bus, while DRAM uses multiplexed addressing with rows and columns and the RAS and CAS lines saying which one you're currently providing.

For small amounts of memory the SRAM was still cheaper, because it was simpler. But 64k of SRAM was expensive. Now you can get 64k of SRAM cheap and it's often not worth the hassle (the c64 reloaded mk2 uses SRAM).

NVSRAM (non volatile static ram) is the one that is battery backed up. There is also NOVRAM which is also used for saves which is slower to write but doesn't need a battery.

 

I certainly wasn't intending to imply DRAM was a new thing. Just that your modern machine you're likely using to browse this forum uses that and not X Gigabytes of SRAM.

 

That's this thing right?
https://oshpark.com/shared_projects/7KkskiCn

I don't fully understand how that site works. Are you ordering a design for them to make rather than from a stock? And I don't get how the solder points for the part that connects to where the ROM on the cart was work.

Also, is the TSOP you used still in production? I have been trying to find one that would match the pinout of the ROMs used in the SNES carts so i would not have to solder in any bodge wires to re-pin it, did you have to re-pin yours?

Wait, what do you mean by it falling apart? In what way?

And I can still socket it? How would I do that if the original is surface-mounted?

And my issue is if I programmed it wrong, especially since I am new to this, which is why I want to socket it. I would want to use that test cart to make sure I setup everything correctly first before I permanently solder it to another cart. Plus I just want to mess around with testing different FX games or settings on that cart.

Yeah, I know I can just get one made, but most of the ones selling those carts tend to not disclose which rom image they use or the donor they used. Plus, I do still want to make a socketed test cart out of Doom to experiment with on my own. But I am still going to have to practice on broken scrap first before I try to do it for real.

 

I could explain, however I believe with the electronic experience you have it would be more beneficial to have someone like bad-ad make you a cart. The mod is trivial if you have the knowledge, experience and tools. Please don’t take this the wrong way, because I encourage you to learn about circuits/soldering.; You’re not ready for this project. Disclaimers aside if you are persistent to do this, you can order the chip that citrus3000psi’s board uses from buyicnow and they will flash it for 50 cents. When you order from oshpark, they print community published pcb designs for you(it takes about 3 weeks) and mail them to you. The edge of the pcb that you were asking about are called castellated vias(half-vias). You use the those to solder to the pad where the old rom was. Remove the rom using hot air.

 

i used this one https://oshpark.com/shared_projects/JSVJHBhz it worked great but i was using 27C801 chips
by @TheRealPhoenix cannot thank him enough for the design

 

You can socket it by soldering wires to each pad where the ROM goes. You just need to be very good at soldering and you can run those wires to a socket which you could try I suppose gluing to one half of the cartridge shell for support. By falling apart I mean if you solder wires to the pads on the board then if the wires are pulled on hard enough for whatever situation you could rip the pads off the PCB. You could glue the wires down on the PCB with hot glue to help give the ends soldered to the board some added protection against being ripped off by accident.

You could also use the PCB drewmerc linked to and then solder wires to the much bigger pads of it and run those to a socket you could mount on the cartridge. Chances are though if you haven't desoldered surface mount parts before there is a high probability you will lift a pad off the board when you try to remove the MaskROM. Especially if you are trying to just heat it with a cheap soldering iron to remove the solder. If you do take a pad off the board it's still possible to run a wire to another place you could get the signal or by scraping off the solder mask and getting to the copper nearby.

Before you attempt desoldering on a Super FX pcb you should find old junk computer boards or broken consumer electronics and see if you can desolder a similar surface mount chip without damaging anything. There are plenty of things to practice on before using the limited supply of Super FX games as practice. Plus that would help you see how whatever equipment you have does in action.

 

(Sorry that it took me a while to reply)

I see, so there is no pre-manufactured surface-to-socket adapter I can use then, I would have to just straight-up solder wires from the surface contacts on the SNES cart to a socket.

Actually, I just realized... would there be any way I can put the TSOP I would flash into that socketed test-cart to make sure it works, and then just straight-up solder it to the permanent cart? Or would I have to solder it to a board with pins in order to socket it, requiring me to un-solder it then re-solder it to something like citrus3000psi or The_Real_Phoenis's boards posted here if I wanted to permanently install it?

I'm not sure what you mean by this to be honest. I am trying to picture how that would work but I am not sure what you are getting at.

But either way would require me to solder the TSOP onto some kind of board wouldn't it? I wouldn't be able to put the bare TSOP into some kind of socket without soldering it to anything additional so that I could then just remove the bare TSOP and permanently solder it onto another cart once I verified that it's working?

Yeah, I am planning on practicing with junk first before attempting this, I also have an extra sonic 3 cart where the FRAM has failed that I figured would be useful to attempt to see if I can fix, since I already have another working Sonic 3 cart anyway, though those are DIP so they would be considerably easier than the surface-mount ICs SNES carts use.

And wouldn't I use something like a desoldering wick instead of putting the iron on the IC pads directly?

 

Hi! Not sure if this video would help. Basically, you can just get a premade blank snes chip and then flash a game on it. Not sure if it has the fx chip you need or not :/

 

No, it does not. That works great for any standard games but no one has yet reproduced the Super FX chip or made any released attempt at simulating its behavior. It's not impossible but it has not been done so far.

 

Ah I see, that’s a bummer then :/