Re: 6581 phase-accumulating oscillators

jbevren_at_starbase.globalpc.net
Date: 2000-11-19 03:57:52

Nate: Doesnt modplay64 use PWM in one of its sid modes?

On Sat, 18 Nov 2000, Richard Atkinson wrote:

> Has anyone ever used the SID's phase-accumulating oscillators together
> with a fast frequency register routine to generate phase-modulated sounds?
> 
> I'm thinking about the possibilities of running a tight loop constantly
> re-writing the high frequency register to add different values to the
> phase-accumulating oscillators in triangle waveform mode to produce
> arbitrary 11 bit waveforms.
> 
> The slew rate is limited by the maximum number you can add to the
> oscillators every cycle, which produces 4kHz triangle waves. However, a
> sinusoidal wave with that gradient at t=0 wouldn't be much lower, and
> there are all sorts of other noises one can imagine.
> 
> This can all done even better on SuperCPU machines where you can write to
> the sound chip every 1MHz bus cycle.
> 
> 
> Richard
> 
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