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PostPosted: Sun Oct 11, 2015 10:07 pm 
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Posts: 47
Hey guys,

On my SNES console (, I'm getting weird glitches on certain games. For example, on Super Mario World, if Mario moves on the map, he disappears:

https://youtu.be/luyovVFl1wI

Here's a video of Pilotwings. The altitude seems to be kind of random (last two or three digits of it seem to be what you would expect for dropping altitude but the rest are definitely wrong!). Besides that it plays fine.

https://youtu.be/ohr8-LxeXkE

Any ideas? Would a certain chip be faulty?
Edit: It's the original North American SNES, not the Jr.

Thanks!


Last edited by SnoopKatt on Wed Oct 21, 2015 12:17 am, edited 3 times in total.

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PostPosted: Sun Oct 11, 2015 10:59 pm 
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When Mario "disappears", are you able to still select the level?


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PostPosted: Sun Oct 11, 2015 11:18 pm 
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Espozo wrote:
When Mario "disappears", are you able to still select the level?

I cannot, button presses don't do anything.

Also, if it helps it's the original North American SNES, not the Jr.


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PostPosted: Mon Oct 12, 2015 8:03 am 
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If I had to guess, this sounds like a bad RAM chip. Do you have any way of running the SNES Test Program?


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PostPosted: Mon Oct 12, 2015 8:38 am 
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adam_smasher wrote:
If I had to guess, this sounds like a bad RAM chip. Do you have any way of running the SNES Test Program?

I don't have a flash cart at the moment but I could figure out a way to get it on a cart. Thanks for the input!


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PostPosted: Tue Oct 20, 2015 9:35 pm 
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I still haven't gotten a test cart yet, but I opened up the system to see if anything looks corroded, and besides from a bit of dirt it looks good. I also took a video of Pilotwings...the glitching follows an interesting pattern:

https://youtu.be/ohr8-LxeXkE

Is there a supply that sells SNES RAM chips, or do they have to be pulled from salvage systems?


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PostPosted: Tue Oct 20, 2015 11:37 pm 
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Unfortunately, I'd suspect a bad CPU. :( I recently repaired a bunch of Nintendo Super System arcade motherboards (basically an SNES, with 3 slots and an extra processor to handle coin operation)... and some seemed completely dead, some would play some games and not others, and some had goofy glitches like yours... but the majority of problems ended up being bad CPUs. Over the last few months I've bought lots of SNES motherboards on ebay (hoping to get some CPUs to repair the NSS motherboards), and quite a few of them also had bad CPUs.

If you really want to get to the bottom of it, I'd definitely recommend the burn-in test cart... though it's probably just gonna tell you what you already know... it's broken (or it won't detect the problem and pass all the tests). To compare... I've only come across 4 bad PPU1s, 3 bad PPU2s, 1 bad APU, and no bad VRAMs or WRAMs.

Here's what 24 bad SNES CPUs looks like. :/

DogP


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PostPosted: Wed Oct 21, 2015 7:45 am 
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Yeesh. I'm surprised games would run so (sorta) well on a bad CPU, and here it seems like very specific addresses giving bad data, which is why I guessed RAM. But there was another big long thread on here of someone diagnosing their broken SNES and it was the CPU too (the whole stack subsystem was busted). I wonder if there's something about the S-CPU's physical composition that's causing them to start decaying rapidly all of a sudden...

Anyway, SnoopKatt, - regardless of if it's the CPU or the RAM, I'm pretty sure the only source for parts would be another SNES; the transplant operation would probably pretty tricky, too.


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PostPosted: Wed Oct 21, 2015 12:19 pm 
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adam_smasher wrote:
Yeesh. I'm surprised games would run so (sorta) well on a bad CPU

The CPU is so integrated that it seems certain parts fail, causing weirdness, but still running. For example, one CPU had a bad DMA controller, which would play a lot of games fine, but for example F-Zero played weird. Another had a bad multiplier and divider, which again played lots of things fine, but the tracks on Mario Kart, F-Zero, etc got really crazy whenever you turned. Others probably had bad address lines or something, because a lot of games would run 100%, and the test cart would pass all tests... but some of the larger/more advanced games just wouldn't run at all.

I'm working on putting together a webpage with symptoms and failures that I've run across, so maybe it'll give an idea of what to expect from various failures. I'll probably try purposefully sabotaging some VRAM and WRAM (lifting/shorting pins, maybe removing and overvoltaging/ESD shocking and reinstalling) to get an idea what symptoms that'd specifically cause.

DogP


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PostPosted: Wed Oct 21, 2015 1:24 pm 
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That's a bummer to hear :/ but thank you for sharing! When I'm able to get a replacement board, I'd be happy to send you the broken board for just shipping costs.

It's a shame new ASIC's are so expensive to make, it'd be great to make new CPU's :(


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PostPosted: Wed Oct 21, 2015 4:04 pm 
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Location: NE Indiana, USA (NTSC)
Perhaps the way forward is to get a working S-CPU, S-PPU1, S-PPU2, S-SMP, and S-DSP decapped, delayered, traced, and into an FPGA.


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PostPosted: Wed Oct 21, 2015 4:26 pm 
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tepples wrote:
Perhaps the way forward is to get a working S-CPU, S-PPU1, S-PPU2, S-SMP, and S-DSP decapped, delayered, traced, and into an FPGA.

Kevtris wants to make a SNES core for his FPGA machine: http://atariage.com/forums/topic/242970 ... tem/page-1
So maybe that's the way to go in the future once all our CPU's die :p


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PostPosted: Thu Oct 22, 2015 1:12 pm 
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Well...

Of course that probably fails to account for any still undocumented behavior yet, but it does seem to run well enough at least.


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PostPosted: Thu Oct 22, 2015 1:35 pm 
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Sik wrote:
Well...

Of course that probably fails to account for any still undocumented behavior yet, but it does seem to run well enough at least.

Nice! Looks like it's still getting worked on too:
http://pgate1.at-ninja.jp/SNES_on_FPGA/

Hope it turns into something we can all use :)

I saw that Super Famicoms are actually cheaper to import than SNES's are to buy online and locally :p I read that the main differences are the RF adapter and the power supply; I have a 9V (center negative) power supply from a guitar pedal and I wouldn't use RF. From what it looks like they're pretty similar size wise too. Would a Super Famicom board fit in a SNES shell?


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PostPosted: Thu Oct 22, 2015 1:39 pm 
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Terrifying about the CPUs.

Even though we have that very well emulated (can count the 'known-unknowns' on one hand), it's a necessary component for software-based reverse engineering of the rest of the chips. And that's the only kind of RE work I am capable of doing. And god knows the PPU needs a whole lot more RE work done.

> http://pgate1.at-ninja.jp/SNES_on_FPGA/
> Hope it turns into something we can all use :)

The author of that one is Japanese, so nobody's ever going to see the source for it.

> I saw that Super Famicoms are actually cheaper to import than SNES's are to buy online and locally

The last time I was in the market, you were looking at about $30-40 (shipped) either way. With outliers trying to get $50 out of you (local game shops, easy to haggle back down to $40.)

However, the AC adapter guys gouge the hell out of you. Asking $20 per adapter + $15 shipping per adapter. I'm just going to go the generic route.

Has this changed recently?


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