Mario Chip 1 sram A15

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gorgyrip
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Joined: Tue Jan 11, 2011 4:41 am

Mario Chip 1 sram A15

Post by gorgyrip » Fri Nov 27, 2020 5:50 pm

I found a schematic stating that pin 97 is sram A15. It's NC, so I connected sram A15 there, but it's not working.

So i have starfox 1+2 on an 29f016. i use A20 to manually select the game.
This flash is connected inside a super famicom box (the hotel console).
Starfox 1 works, but for starfox 2 i only get some audio and a black screen.
I removed the 32k sram and added an 128k sram (A16=gnd, CE2=VCC and A15=pin97 of Mario Chip)

Is the pinout wrong? Maybe Mario Chip can support only up to 32k of sram.
PS: on GSU-1 pin 97 is indeed sram A15.

Pokun
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Re: Mario Chip 1 sram A15

Post by Pokun » Sat Nov 28, 2020 1:41 pm

As far as I know there are three known variations of the Super FX: Mario Chip 1 (Star Fox only), GSU-1 (most other games) and GSU-2 (Doom and Yoshi's Island). The only differences are pinout, how much it can address and usable clock speed according to Wikipedia. Mario Chip 1 doesn't have enough pins for all later games needs.


gorgyrip
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Re: Mario Chip 1 sram A15

Post by gorgyrip » Sun Nov 29, 2020 6:21 am

Thank you. From your link by wuertymodo:
"I'm looking at a Star Fox 1 PCB now which has the MARIO chip, and I can confirm that there is no oscillator on the board, so it uses the cart edge clock signal. Also, I tried putting Star Fox 2 on a Star Fox 1 PCB, and this is what I get:

https://www.youtube.com/watch?v=b0FgyKq4b0o

I forgot to say that was what I got AFTER replacing the SRAM with 128KB (with the high address bit tied to Gnd, so 64KB active). I'm not sure if the MARIO chip even supports 64KB SRAM. There was one unused pin on the MARIO chip between SRAM A14 and SRAM /OE, so that's where I connected the SRAM A15 pin. With the original 32KB SRAM, all I got was a black screen with some of the audio that eventually just trailed off to the percussion track looping with nothing else."

It seems Mario Chip doesn't have sram A15.

nocash
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Re: Mario Chip 1 sram A15

Post by nocash » Sun Nov 29, 2020 1:25 pm

How do you dinstinguish between "doesn't work don't know why" and "doesn't work because A15"?
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tepples
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Re: Mario Chip 1 sram A15

Post by tepples » Sun Nov 29, 2020 1:53 pm

To determine whether a Super FX game needs SRAM A15, try running it on a GSU with only 32K of RAM. If it runs, then it doesn't need A15.

gorgyrip
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Re: Mario Chip 1 sram A15

Post by gorgyrip » Mon Nov 30, 2020 3:56 am

nocash wrote:
Sun Nov 29, 2020 1:25 pm
How do you dinstinguish between "doesn't work don't know why" and "doesn't work because A15"?
tepples wrote:
Sun Nov 29, 2020 1:53 pm
To determine whether a Super FX game needs SRAM A15, try running it on a GSU with only 32K of RAM. If it runs, then it doesn't need A15.
I just tried starfox 2 on GSU-1 with only 32k of sram. It does the same (black screen and some music playing). So definitely sram A15 is needed.

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