Adding battery backup to snes repro (i.e. Doom for SF2)

I just remembered that I did this recently and someone else might be interested.

I did a write up here: http://www.omgrofl.com/?p=23

It was a rush job - mostly to see if it worked. I intend to revist it once I get time to use an off the shelf part rather than using 2 donor carts.

 

You can use Super Mario World 2 Yosh's Island that has battery and does have the fx2 chip.

 

half the amount of sram tho.

Its covered in my write up.

 

Oh..

a friend of mine that is a user in this forum said he would do a star fox 2 reproduction for me and I remember he saying that he would add the amount of ram. Since he said that I think this is the best way to go.

I'll ask him if he can drop by any give us some explanations.

 

Yoshi's Island has the place for the bigger SRAM chip (I put an 128KB chip instead of 64KB) so I could put TWO GAMES on the cart and have both save at same time.

The only catch about using Yoshi's island is that you have to grab SRAM A15 from the respective pin on the GSU chip. Also you have to remove the 32KB SRAM chip and scratch the pads for the 128KB chip, along with two or three traces you need to cut.

The point is that Starfox 2 is a GSU2 game and if you don't want it to slowdown and bog down underclocked by using an GSU1 chip you have to find a board with GSU2... :shrug:

So I made an Starfox/Starfox2 cartridge on a Yoshi's island board:

As you can see, I replaced the 62256 chip with an old128KB SAMSUNG SRAM.

This is a SA-1 which is much mod friendlier as it's reading the TSOP chip in 16 bits which allowed me to drop in an 29LV322 straight.

(Diodes and resistor are there to drop the flash chip power to 3.3v)

Edit: The SA-1 game is Jikkyou Oshaberi Parodius.

 

l_oliveira needs some flux remover. :thumbsup:

Nice job on dropping in the TSOP chip.

 

I don't clean the flux because it's of the no clean type (comes with the solder, I pay premium for that kind of solder ) and in the end it helps protecting the board and chip pins in the long run. :thumbsup:

Also it's one thing less for me to do.

 

l_oliveira is a far better solderer than I

 

Im using 2 TSOPS for some Secret of mana 2 (Seiken Densetsu 3) rather than a using 6 chips.

Not much point posting pics as its been done before tho.

Its nice to see a different approach taken tho - everyone sees things differently (me adding battery vs you adding sram)

Also l_oliveira, where did you get those TSOP48 to PSOP44 pcbs? id really like some of those

 

The adapters and flash chips came from scraps. I got them from broken neo geo MVS botlegs. :thumbsup:

I wish I could find the Chinese maker I would buy a bunch of them ...

 

Do you have any more?

I could probably copy them in eagle and it would be much easier with one in hand - then send off to get a batch of 100 or so made.

 

I can scan one of them for you.

There is two kinds of them

for 29F016 and for 29F160/322 (also probably works for the 64MB version)

I have a lot of the 8 bits one (28F016) but I'll see if I can dismantle the SA-1 cart to take the adaptor out of it.

Also if you could make TSOP to DIP adapters it would rock a LOT :thumbsup:

 

I agree, they are extremely handy. I searched all over for tsop to sop footprint adapter.

Let me know if you pull one out or if you want to do a trade? I can swap you a starfox2 done with a dip chip for one of yours with tsop adapter - that way you are not down a game.

And if i get a clone done, you will have an endless supply

 

Starfox isn't soldered straight to the board. There's no commercial flash chip which matches the maskrom pinout used there. So you won't escape from making a custom layout on that one.

The ones I have are generic. The SA-1 board uses an JEDEC pinout MASKROM (Same pinout as SEGA 16 bit maskroms btw) and that's why I could drop it straight.

 

just means having more types of adapter, wont be too hard once the footprint is sorted out.

Let me know if we can arrange something to get one of those adapters into my hands. Ill pay all the shipping etc.

I prefer things to look tidy and correct, so i want to get these made

After one of each type you have + ill edit the pinout for GSU1/2

 

For the last few years I've been using some basic solder that was likely produced in the 60s or 70s. 60/40 lead/tin classic stuff my grandfather had kicking around his garage. Doesn't have inbuilt flux but my flux pen handles nicely overall. Never heard anything about flux protecting the board before, usually see people unusually anal retentive over the look of the board rather than function and reliability.

I've been looking for a circuit to build for the battery approach for some time as well, thought I found a good one for NES repros on a French forum but between my poor French, a French dictionary and an inconvenient 404 I couldn't figure out which graphic was the final design.

A drop in board would be quite nice, one more reason for me to buy a quality programmer.

 

Lemme add a suggestion for SRAM backup:


I like Mitsumi MM1026 SRAM watchdog chip. So does Konami (It's what is used as watchdog on their famicom carts with SAVE capability).

What I do is hook the non inverted chip enable signal of the RAM (when it's a 6264 or 628128 chip) to the watchdog chip.

If it's a 62256(32KB) or 628512(512KB) chip I use two ports of an 74LS32 to OR the original chip enable coming from the system with the read and write strobe signals.

That allow the use of the chip select pin of the SRAM for memory protection purposes. :thumbsup:

MM1026:
http://www.alldatasheet.com/datasheet-pdf/pdf/86807/MITSUMI/MM1024.html

Should be very easy to find in both DIP and SOIC packages.

 

You wasted a Stunt Race FX board. GSU-1 features the 21mhz High Speed Mode that GSU-2 had too. GSU-2 can address more ROM and is the only operational difference I am aware of. People pass misinformation off about Star Fox 2 needing "Super FX2" or else it suffers slowdown or something like that. "Super FX2" doesn't exist and Star Fox 2 naturally will have places with slowdown.

Doom, Yoshi's Island, Winter Gold. All these need GSU-2 not for some performance boost, they all need the ability of the GSU-2 to address 16 megabits of ROM. GSU-1 cannot do this. Super FX has a register for clock rate control. GSU-1 games set this to High Speed mode (21mhz) too.

If you do not believe me, test Star Fox 2 on a GSU-1 board. Star Fox 2, like other GSU-1 games also enables High Speed mode. Disabling high speed mode the game does run slower than intended. But the fact remains that GSU-1 can and does run at 21mhz. Mario Chip (Star Fox 1) can't run in High Speed mode.

 

You are correct, I have since found all that out. My comment was based on that same misinformation you are talking about.

When I finally got around to using an off the shelf replacement for the chip, I was going to edit up the post.

However, I didnt waste anything. The parts were removed for proof of concept, they are now back on the original board.

This is what happens when you read things on the internet (including wikipedia that mentions Super FX2) - its not always right.

 

What would it take to convince someone to make a Starfox 2 repro? I can do cash and am willing to find the proper donor cart. If anyone is interested at all, please PM.

BTW, I am looking for someone to burn a translated Star Ocean to a chip for me as well. Same offer as above.