Re: Emulating a SID (or sort of)... with a 65xx.

On 8/29/20 11:27 AM, groepaz_at_gmx.net wrote:
> Am Samstag, 29. August 2020, 03:36:47 CEST schrieb tokafondo:
>> Everybody building a SBC that wants sound output gets to the same wall:
>> There are not sound generators, or programmable sound generators, or such
>> kind of chips available like they were 30 years ago. Yes, you can get them
>> a pulled ones, or old stock, or you can go the FPGA, PIC or Arduino route
>> and get one of those sound cores that end being more powerful than the SBC
>> itself, just to get SID or FM sound.
>>
>> There has been discussions about getting funcion generator chips, couple
>> them to an external amplifier chip, and use them to generate waveforms based
>> basic sounds.
>>
>> And I even read recently as having a 6502 CPU in a SBC just to generate
>> sound.
>>
>> So... How difficult could be to get a 65xx CPU, have it generate a waveform
>> with its ADSR settings, process it applying filters or whatever, and
>> bitbanging it to a DAC, to generate sound?
>>
>> In another words: how feasible would be to implement a sort of SID (or
>> whatever other generic PSG chip) engine in a 65xx chip, that could be used
>> inside the same cpu, or act as an external sound chip for a main CPU? Do
>> exist such a thing?
> 
> it wasnt uncommon to do this in arcade machines, for example. entirely
> possible. you wont get fancy filters, but everything else isnt terribly hard
> to do.

Or see the ZX spectrum, the soundgenerator was the same single I/O-Bit 
that was used for the tape interface. It could be turned on or off. The 
rest was software.

A 6502, a ROM and a 6532 plus a simple R2R-DAC could be used as a 
soundgenerator. Not sure if that's a good idea, but it could be done.

  Gerrit