N64 cart modding

CaptainN · Post by **CaptainN** » Tue Mar 10, 2009 4:11 pm

I recently built some SNES cartridges using tutorials I found with detailed information on how to replace the mask rom with an eprom. It's pretty cool, and fairly easy to do. For the N64 I can't seem to find any information on this topic however. Does anyone here know if it is possible to replace the rom on the cart?

themadhacker · Post by **themadhacker** » Tue Mar 10, 2009 5:23 pm

possible? I don't see why not.

jleemero · Post by **jleemero** » Tue Mar 10, 2009 5:31 pm

Yes and no.
But in a much simpler sense, no.

Marshallh has a much better understanding of this than I do, and he could explain exactly why it is that this can't be done.

stuntpenguin007 · Post by **stuntpenguin007** » Sun Mar 29, 2009 11:23 am

for one try and find a 32mb eeprom... not gonna happen.

marshallh wrote:Not gonna work. The address and data lines are multiplexed. You'll need some 74 series logic to buffer the address and latch it in.

The chips on the cartridge PCBs are mask ROMs - they have the decoding circuitry built in.

The other problem is finding a DIP flash ROM big enough (eeproms are hard to find much above 512k). You'll likely have to use a tsop44 NOR flash rom.

Link83 · Post by **Link83** » Mon Mar 30, 2009 6:43 pm

stuntpenguin007 wrote:for one try and find a 32mb eeprom... not gonna happen.

marshallh wrote:Not gonna work. The address and data lines are multiplexed. You'll need some 74 series logic to buffer the address and latch it in.

The chips on the cartridge PCBs are mask ROMs - they have the decoding circuitry built in.

The other problem is finding a DIP flash ROM big enough (eeproms are hard to find much above 512k). You'll likely have to use a tsop44 NOR flash rom.

I'd still be interested to know how to make one if its possible? Even if it does require extra logic chips to get it to work.

I guess another option would be an N64 flash cart, but I dont believe anybody has managed to make one yet? (Apart from the now very expensive V64jr/E64)

Post by **marshallh** » Mon Mar 30, 2009 9:28 pm

The address and data lines are muxed into 16 combined lines, and a simple address latching scheme is used. Addresses are latched every 256 words, but reads are not necessarily 512byte block aligned.

If you really want to do this, the information is out there. You will need to do a lot of reading up, though. You will be lucky to get a 8mbit game on there. The smallest N64 game ever made is 32mbits, the biggest ones are 512mbit. See the problem?

The biggest parallel NOR flash you can get is 64megabit, in a TSOP44 package. And you won't be using those without building a custom PCB first.

If anyone wants to donate money I'll build this flash cart design I've been sitting on for half a year

eurddrue · Post by **eurddrue** » Mon Mar 30, 2009 9:41 pm

How much money would you need to finish the project? And how much would you be selling them for?

Link83 · Post by **Link83** » Tue Mar 31, 2009 9:04 am

marshallh wrote:If anyone wants to donate money I'll build this flash cart design I've been sitting on for half a year

I would be very interested!

Same questions as eurddrue - how much would be needed, and how much would you expect the completed flash cart to cost? I am sure we could gather enough interest judging by the Neoflash project that never happened:-
http://www.neoflash.com/forum/index.php ... 217.0.html

If you dont mind me asking I would also love to know what capabilities the flash cart would have, such as:-

-Could data be transferred over USB?
-Could it include or 'mimick' all original cartridge save types?
-What would be the maximum storage size?
-Would an SD card slot be feasible?

I would imagine the easiest way to impliment the CIC would be to have a DIP socket on the PCB so that you can take a CIC from cheap N64 game(s)? This way you wouldnt need a cartridge slot on the cart (Assuming you could impliment all the save types somehow) and you could also switch CIC chips when needed. Also, if a clone CIC is ever created it should be relatively easy to connect it up.

I really hope this can become a reality

Post by **marshallh** » Tue Mar 31, 2009 1:58 pm

One of the reasons I haven't gone ahead and built this quite yet is I'm waiting on a friend who is working on decapping the CICs and getting the keys from them.

If not, I'll be integrated a universal boot emulator into it for all non-6102 cics. You will be required to source a 6102 of your own (NFL or WWF wrestling, any 3rd party game)

Saves are harder. I'm not bothering with saves this time around. Using save-patched ROMs for now.

Link83 wrote: -Could data be transferred over USB?

No. Maybe later, definitely doable with a FTDI usb fifo.

Link83 wrote: -Could it include or 'mimick' all original cartridge save types?

Yes, later.

Link83 wrote: -What would be the maximum storage size?

Whatever the N64 can address. Reads are relayed to the Compactflash card in real-time so there is theoretically no limit.

Link83 wrote: -Would an SD card slot be feasible?

No.

The first stuffed proto PCB will run me about $100 which I don't have now. The final price will be less, but keep in mind you will not get huge discounts you get producing huge runs in Chinese factories.

Link83 · Post by **Link83** » Tue Mar 31, 2009 2:35 pm

Wow, so compact flash cards? Thats even better than the SD cards I was hoping for!

I really think a cart save ability would be a great feature to include if at all possible (and possibly USB, as most modern PC's dont even seem to have parallel ports anymore

)Although if it really uses a Compact Flash card a USB card reader doesnt cost much

Would a simple boot menu system be possible or would it be a case of separate compact flash card for each game?

Regarding the CIC, I read a while ago that the 'Guru' was working on decapping the N64 CIC's but I dont know how far it progressed. There was a lot or work done on decapping the NES CIC's at the nesdev forums which are supposedly almost identical to the SNES/N64 CIC's, and I believe someone is/was currently trying to look into the SNES & N64 CIC's, although im sure you already know all this.

Even if we have to rob a CIC from a game, theres quite a few third party N64 games I think would be suitable (Im looking at you 'Tigger's Honey Hunt' and 'Elmo's Letter Adventure'

)

Oh, and I havent ever used a 'Universal Boot Emulator' but can it support PAL CIC's?

Post by **marshallh** » Tue Mar 31, 2009 6:56 pm

final board will be smaller of course... this is how it stands

eurddrue · Post by **eurddrue** » Tue Mar 31, 2009 7:02 pm

so it's not going to be n64 cart sized? do you have a case all picked out?

Post by **marshallh** » Tue Mar 31, 2009 7:27 pm

eurddrue wrote:so it's not going to be n64 cart sized? do you have a case all picked out?

marshallh wrote:final board will be smaller of course...

Reading is good for you. do you know what a prototype is?

thewise1 · Post by **thewise1** » Tue Mar 31, 2009 7:33 pm

Hopefully though you can put the cart slot on top if you don't get the boot device integrated into the system, if it's on top then it will still be compatible with all of our portables. I hope you can finish this though. It would be so much easier to carry around your games than all of the carts.

Mario · Post by **Mario** » Tue Mar 31, 2009 9:30 pm

Very nice work. I can't wait to see it finished. I'm assuming the LEDs and numerical display are for debugging?

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