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MVC2 bad rom chip - is this normal?

jeremania

jeremania

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I recently purchased a Sega Naomi with a Marvel vs Capcom 2 cart from @tonyt76 and the rom board test shows a bad IC14 64M rom chip.

Is this normal, expected behavior for a "tested/working" MVC2 Naomi cart?
1000001827.jpg


The listing is here for reference: https://www.arcade-projects.com/threads/naomi-w-marvel-vs-capcom-2-capcom-i-o.29849/
 
What are you using for a power supply? The Naomi is very picky. Make sure your 3.3v & 5v are as close as possible.
 
Is the IC22 a factory chip or does it have the unlock done? I'm not sure if that affects code in that region, or the checksum. If the IC22 is an original sega one, I'd wager either the checksum of IC14 is bad, or it's malfunctioning in a way that has not caused any problem(s) to this point. Of course that is speculation but that's where I'd be at; verify and even maybe replace IC22 since it's socketed, and re-run the checksums to see if IC14 not only shows bad but also consistently returns the same BYTE/WORD result. If the result itself changes then that chip isn't dumping the same content every time it's checked so BAD would be different as opposed to BAD if it's the same, but 'incorrect', value every single time. Hope this helps.
 
Thank you both! Looks like this isn't normal behavior for a MVC2 cart. Because unlocking IC22 doesn't affect code in that region, either the checksum is bad or the rom is malfunctioning. No need to verify/replace IC22. Am I understanding this correctly?
 
jeremania said:
Thank you both! Looks like this isn't normal behavior for a MVC2 cart. Because unlocking IC22 doesn't affect code in that region, either the checksum is bad or the rom is malfunctioning. No need to verify/replace IC22. Am I understanding this correctly?
Click to expand...
Yes sir! Especially if you can just verify IC22 in a programmer, since it holds what's considered to be the valid sums for the other roms. But I would think you have a good understanding now :)
 
IC14 sum should be 60E5/C4CD, not much difference compared to numbers shown of the photo. probably few bits bitrot in this mask ROM. not fatal, you can live with that :)
 
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