Difference between AY-3-8910, Yamaha YM2149F and Texas Instruments SN76489 sound chips?

Question

All 3 of those sound chips are very similar in functionality, and provide either 3 square wave channels, or 2 square wave and one white noise channel (any of the 3 square wave can be turned into a noise generator but there is only one noise source). It also seem all 3 can only provide a 50% duty cycle on the square wave channels (unless I missed something).

According to this source, the Yamaha YM2149F is just a Yamaha clonse of the AY-3-8910 chip, so it means its possibilities are very close.

So, what are the difference between those 3 sound chips?

Answer 1

The AY-3-8910 you mentioned is a three voice sound chip.

It provides all the functionality you mentioned above. But also has tone/noise mixing for all three voices. The global noise generator has a 5-bit period table. Something else you get with the AY is a global-only volume envelope generator, which rapidly manipulates a channels' volume register to generate saw or triangle waves.

The YM2149F is just a Yamaha-branded AY-3-8910 made under license. The clock frequency is twice as high as the General Instrument version. It was also the analog sound component called the "SSG" (Software-controlled Sound Generator) of Yamaha's OPN chip family, but was not used in the YM2612.

The Texas Instruments SN76489 is different. It is a four-voice chip with three pure tone generators and one noise channel. The noise channel only has three tones it can produce by itself. Fortunately, the third square channel has to be muted in some way, which gives the noise channel its full frequency range. The noise channel also can produce a 6.25% pulse wave as a second noise mode. There is no volume envelope generator.