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PostPosted: Wed Oct 05, 2022 6:24 pm 
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I believe I’ve gotten my hands on some NES/Famicom clone IC’s - I believe the 6527 is the 6502 derived CPU and the 6538 is the PPU but I’m unsure about the rest..

Anyone here have more data on these IC’s? In the other thread here I found a schematic but nothing else.

Strangely the packages are so dissimilar they look like they’re from different fabs

Edit: And yes, they were cheap.. but:
You get what you pay for! https://youtu.be/RyR7n50a7YM


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PostPosted: Fri Oct 07, 2022 6:27 am 
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I *think* this is probably what they are:

UM6526N - An UMC CIA, probably compatible with the MOS6526 CIA (That's a reasonable assumption, right?)
UA6527 - A clone variant of the NES 6502, aka the Ricoh 2A03
UA6528 - PPU, NTSC version
UA6538 - PPU, PAL version

I wonder how much the PPU's have in common with the Ricoh PPU - https://www.nesdev.org/2C02%20technical%20reference.TXT or the TMS9918 for that matter.

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PostPosted: Fri Oct 07, 2022 7:22 am 
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AndersNielsen wrote:
I *think* this is probably what they are:

UM6526N - An UMC CIA, probably compatible with the MOS6526 CIA (That's a reasonable assumption, right?)

Dunno about that. CSG wasn’t known for second-sourcing chips that were only used in Commodore computers. It would be interesting to learn if the UM6526N was an exception.

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PostPosted: Fri Oct 07, 2022 8:52 am 
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There's plenty of info on some of these chips on the NESDev wiki. The CPU and PPU are close enough to the original to run the games, but do have some timing differences. It should be relatively easy to make a working system out of them. the 6527 has a sound generator and some I/O in addition to the CPU I think.

There's a list of known chips at https://www.nesdev.org/wiki/CPU_variants, no 6526 in there though.


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PostPosted: Mon Oct 10, 2022 6:45 am 
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BigDumbDinosaur wrote:
AndersNielsen wrote:
I *think* this is probably what they are:

UM6526N - An UMC CIA, probably compatible with the MOS6526 CIA (That's a reasonable assumption, right?)

Dunno about that. CSG wasn’t known for second-sourcing chips that were only used in Commodore computers. It would be interesting to learn if the UM6526N was an exception.


The jury is seemingly still out on what the UM6526N is - maaaybe it's an NTSC TIA. Maybe it's a CIA. Maybe I can test my way out of it.
https://forums.atariage.com/topic/29560 ... he-um6526/

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PostPosted: Mon Oct 10, 2022 10:13 am 
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AndersNielsen wrote:
The jury is seemingly still out on what the UM6526N is - maaaybe it's an NTSC TIA. Maybe it's a CIA. Maybe I can test my way out of it.
https://forums.atariage.com/topic/29560 ... he-um6526/

(Watching for a rising mushroom cloud to the east) :D

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PostPosted: Mon Oct 10, 2022 5:04 pm 
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The 6527 and 6528 have suspiciously "gritty" mould marks in those shots. Thy don't look as clean and smooth as the other 2 chips. Is there anything printed or embossed on the under side of the chips to help identification?


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PostPosted: Mon Oct 10, 2022 6:42 pm 
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Martin A wrote:
The 6527 and 6528 have suspiciously "gritty" mould marks in those shots. Thy don't look as clean and smooth as the other 2 chips. Is there anything printed or embossed on the under side of the chips to help identification?


I agree. But the underside seems to indicate they are from UMC - or at least the same FAB. Can't remember exactly and can't take a photo right now though.

But I think it's about solved - I found this Atari 2600 Jr photo on Wikimedia. I believe that solves the mystery - it is, in fact, a TIA chip :)

Image

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