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PostPosted: Sun May 29, 2016 7:16 pm 
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I'm looking for the sram datasheets from either doom (LH52A512NF-10TLL) or stuntrace FX (KM68512LG-7).

What I am trying to do is upgrade a Yoshi Island's sram from 256Kb to 1Mb. Why? Because from looking at the Doom PCB found here it has 512K/1M. Now I know SuperFX games never use 1M of ram but from what Doom's PCB suggests Nintendo planned to have SuperFX games to have at most 1M of ram. I wanted a cart that maxes out to that spec for the most compatible superFX cart for shits and giggles.

I have hit a snag in researching though. Finding the pin out on the larger sram SFX games has not been easy. The closest thing I could find is this and that can't be right because looking at Yoshi Island I can see pins 1, 30, and 32 are connected to power or ground and Doom looks to have pin 22 is also connected to ground so these chips are not matching up with the datasheet I found.

Thanks for any help and info.

Also if anyone wants to make my search for buying a 1M sram chip easier by telling me where I can get one that would also be cool!


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PostPosted: Sun May 29, 2016 11:47 pm 
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http://problemkaputt.de/fullsnes.htm#sn ... tsgsuchips

All you actually need to know is the pinout of a SRAM that you can actually get your hands on; the pinout of any one on the PCB can be determined from the pinout of the GSU.


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PostPosted: Mon May 30, 2016 3:11 am 
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http://pdf.datasheetarchive.com/indexer ... 078620.pdf


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PostPosted: Mon May 30, 2016 4:29 pm 
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lidnariq wrote:
http://problemkaputt.de/fullsnes.htm#snespinoutsgsuchips

All you actually need to know is the pinout of a SRAM that you can actually get your hands on; the pinout of any one on the PCB can be determined from the pinout of the GSU.



I wanted to avoid making an adapter but it's looking more like I'm going to have to because finding something compatible doesn't seem to exist anymore.


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PostPosted: Tue May 31, 2016 1:15 am 
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pipes wrote:
lidnariq wrote:
http://problemkaputt.de/fullsnes.htm#snespinoutsgsuchips

All you actually need to know is the pinout of a SRAM that you can actually get your hands on; the pinout of any one on the PCB can be determined from the pinout of the GSU.



I wanted to avoid making an adapter but it's looking more like I'm going to have to because finding something compatible doesn't seem to exist anymore.


The SRAM on a DOOM is no different (other than size) than what's used on Yoshi's Island. BOTH can use a commonly available AS6C1008 if you can mount it (on Yi). No adapter required. The Yoshi's Island sram (256k) is PHYSICALLY a smaller package so you might have some difficulty mounting the bigger sram but it won't matter (make this a bit easier for you since you don't know)... because the would-be A15 (pin31) has no connection to the GSU2 which is why the would-be pin 31 is also connected to pin 32 (sram vcc). The difference of doom is because DOOM doesn't use save ram so it just grounds the chip enable line (vs. Yi has that line going to the battery controller chip). It is true that the GSU2 does have a max SRAM A16 pin but it's not used and "maxing" out the sram isn't going to help performance.
If you would have taken the data sheets (like I suggested from YouTube when you asked there) of the 256k sram / 512k sram and now the 1mbit sram I mentioned this post, you'll see that they are all pin compatible with a few difference between the 28 pin 256k and the 32pin 512k/1m but you'd also see that the second enable line lines up with the 28pin sram power pin (pin28)-- that second enable line need to be high to enable the sram -- and it does because it sits on the pin28 (of the 256k sram). SO they really do all line up nicely except the 32pin package is a wider footprint compared to the Yi 256k sram.
To be clear, DOOM does use sram A15 (pin31) so maybe this helps....good luck.


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PostPosted: Sat Jun 04, 2016 10:45 am 
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I put a 1Mb SRAM chip on a Yoshi's Island cart before. I know I took a couple pics of it. If I can find them, I'll post them here if that'll help you out.

edit:

Image

Image

That's a Yoshi's Island cart. The pads that are silver (they're tinned) are the pads for the original 256K SRAM that came on the cart. The pads that are copper were covered with the green solder mask, it's easy to scratch off. These pads will accept the larger SOP package, no adapter needed.

This is the 1M SRAM that I used:

http://www.mouser.com/ProductDetail/ISS ... 252bXdk%3d

http://www.digikey.com/product-detail/e ... ND/1555414

The only modification you have to do to the PCB is cut the trace to pin 31. On the PCB, pins 30, 31 and 32 are all connected to +5v. Pin 31 on the 1M SRAM is A15, so you have to cut that trace and use a jumper wire to connect it to a pin on the GSU. Sorry, I don't remember which pin on the GSU is A15. I don't know if a pinout for the GSU is floating around, but I definitely remember that A15 is right next to A14 or A16 (probably both) and it's really easy to identify since there's no trace going to it.


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PostPosted: Thu Jun 16, 2016 10:49 am 
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Ziggy587 wrote:
I put a 1Mb SRAM chip on a Yoshi's Island cart before. I know I took a couple pics of it. If I can find them, I'll post them here if that'll help you out.


I love you!


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PostPosted: Sat Jun 25, 2016 6:11 am 
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pipes wrote:
I love you!


Image


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PostPosted: Sat Jul 23, 2016 9:54 pm 
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Ziggy587 wrote:
Image


Dude you do rock! 1Mb RAM installed successfully! So happy!

Got off work and I got everything in the mail. I was so excited to get it working I stayed up all night getting it installed to the point where I got tired and fucked up some of the pins. As I was soldering on the wire, my hand just spasmed out from my tiredness and concentrating on such tiny pins. Bent like 3 of them on the GSU and getting solder everywhere. Also pulled up the pads as well and one broke off. I was so pissed at myself! I knew better than to be doing something like that when I needed sleep.

Came back to it later after my bad mood from it passed and fully rested I cleaned off the solder and checked continuity and even though two of the pads lifed and pins bent they seem good and not shorting each other. Next I scrapped off some of the trace to the broked off pad and used a fine strand of solder wick to bridge the pin to the trace. Then I soldered on the wire and recheck continuity to everything. All check out and works perfectly!

Had loads of fun! Now all that is left is to take off the mask ROM and fit on a zif socket!

Another question though. Do you have any software that tests the full 1Mb? If not I think I will probably take on that project!

Image


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PostPosted: Sun Jul 24, 2016 6:14 pm 
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pipes wrote:
Do you have any software that tests the full 1Mb?


Nope. I don't know of anything for the SNES that uses that much SRAM. A friend had supplied me with a Yoshi's Island cart and asked me to put Star Fox 2 (requires 512K) on it for him. The only reason why I went with 1M is because there were no options between 256K and 1M that was 5v tolerant (at least, none that I found on DigiKey). At the time, all of the examples I was able to find in a Google search of people putting 1M SRAM on a SNES cart were also putting multiple ROMs on the cart. They toggled the SRAM with the ROMs so each game could have it's own "save file". You could try this.

pipes wrote:
If not I think I will probably take on that project!


If you're gonna make something for the SNES that will use 1M of SRAM... Can you fix Sim City? :D


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