AY-3-8910 vs AY-3-8910A

FLTCHRR

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I've recently been trying to repair a Frogger and a Super Cobra that are both playing without sound. I ended up harvesting some known working AY-3-8910 chips from a Scramble board I had on hand and that managed to bring the sound back in both boards. I read that AY-3-8910A chips are drop in replacements for the out of production AY-3-8910 so I bought a set of 6 to have on hand. The problem is that they don't seem to be working as replacements. So as far as I can figure, I either somehow got 6 duds, or the AY-3-8910A doesn't actually work as a replacement when used on these older Konami/Gremlin boards. I've been searching around, but I can't seem to find any threads on this. Any help would be appreciated!
 
They are compatible.

Fakes? :unsure:🤷‍♀️

Bought a couple of AY-3-8910 off ebay. They were much quieter than normal, but they work.
 
Thanks for the advice! I was kind of guessing that was the case. I did get them from China off of eBay – I'll hunt around for a better source and try again.
 
Even if they're not fake, they could be "customized" versions with custom address bits, which allow multiple chips to be addressed by the same processor.

That's described in the datasheet, and the Wikipedia page also mentions it: https://en.wikipedia.org/wiki/General_Instrument_AY-3-8910
Although there are only 16 registers, the four MSB bits of the 8-bit bus must be set to the factory default '0000' value when selecting a register. Incorrectly setting the MSB bits causes the chip to ignore the register change. GI did take orders for customized MSB bits (factory set to other than '0000'). The chips made with customize-set MSB register bits allow the same processor to control more than one AY chip on the same bus (e.g. TurboSound for ZX Spectrum). There are many new-old-stock (NOS) chips on the secondary market with MSB bits factory set to a non-'0000' value. The non-'0000' value can cause significant developmental troubles for designers and repair technicians. Software must be written to identify the correct value of the MSB bits on any given chip. Also, software must be changed or hardware added to allow these factory-set-MSB chips to be used in place of the default '0000' chips.

Regarding your direct question - supposedly the 'A' variant provides improved compatibility according to this page: https://www.msx.org/wiki/Microchip_AY-3-8910A .

DogP
 
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