[sdiy] TI 76477 Space Invaders sound chip detailed analysis

Eric Brombaugh ebrombaugh1 at cox.net
Wed May 23 07:49:48 CEST 2018


Yeah, saw that a few days ago. It's a fascinating dive into the old
chip and sure brings back some memories of my mis-spent youth in the
late 70's when I'd buy those chips at the neighborhood Radio Shack and
then wire up all those pots and switches to make weird noises.

Of course if you're looking for a software controlled recreation, the
go-to is the one that the folks who did the MAME game emulator did:

https://github.com/mamedev/mame/blob/master/src/devices/sound/sn76477.c
pp

I suppose I'd be surprised if there's enough demand for this sound to
make it a viable product worth re-imagining for today's market
though...

Eric

On Wed, 2018-05-23 at 06:16 +0200, cheater00 cheater00 wrote:
> I've just found this while surfing the internet, an analysis of the
> 76477 sound chip's digital sound circuits. This includes the unique
> shift-register based noise circuit, as well as the noise filter
> circuit (which is analog):
> 
> http://www.righto.com/2018/05/inside-76477-space-invaders-sound.html
> 
> Here's an earlier anysis of the analog circuitry:
> 
> http://www.righto.com/2017/04/reverse-engineering-76477-space.html
> 
> I wonder if anyone has tried cloning the chip for synth use, with
> modern features like eg tuning.
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