Hello All,

I have a question about a 2A03 found in my NES that looks unlike any other I have seen before, and I was hoping someone may be able to identify it. Generally the 2A03 has a format of text stamped on the front. This one looks totally different. My best guess would be it’s made by Rockwell although it’s lacking the Rockwell logo. The bottom of the chip is stamped “Mexico”. I know that Rockwell made 6502’s but not 2A03’s for Nintendo. As far as I’m aware, only Ricoh made CPU’s for Nintendo and there was no second source chip manufacturer that I know of. There is absolutely no documentation I can find online about this chip. Can anyone help? Thanks!

Most likely it *is* a Ricoh. Your variant is on this page, second row, second column differing only in the date code. https://www.nesdev.org/wiki/CPU_variants

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I was always under the impression that only Rockwell manufactured out of Mexico. They are also one of the only chip suppliers that don’t have the 2 little circles (not sure what they’re called) on top of the chip. Could it be possible that Rockwell manufactured some chips for Ricoh as a 3rd party to help with supply issues?

It's entirely possible it's a Rockwell second-source, but usually those would have a Rockwell logo on them. Alternatively, sure, it could have been a contract fabrication.

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Machine room: http://www.floodgap.com/etc/machines.html