"Market" for old macs?

[Tony Duell]

> 
> > Last trivia question for the day/night:  I own Studio Session (the reason I 
> > keep a mac 512 around) and I swear I am hearing 6 digital voices from it 
> > simultaneously.  I was under the impression that the Mac sound hardware was 
> > only 4 digital voices, and that the extra 2 voices were done via realtime 
> > mixing on two of the channels -- however, literature from the time claim that 
> > Jam Session/Studio Session use "hardware tricks" to get the extra 2 voices. 
> > Who is right?
> 
> Neither really. The original Mac sound hardware had four *synthesis* voices,
> which could be fed a waveform and act as a primitive wavetable synthesizer.
> This produces four-note polyphony.

I don't know what you consider to be 'original Mac', but the Mac+ sound 
hardware was a pulse-width modulator loaded from a spare byte in the 
video RAM area at the end of each video line. Actually, the complete 16 
bit word was loadrd into 2 PWM circuits (curiously one used TTL counter 
chips, the other was in a PAL), the other circuit was used to control the 
drive motor speed on the 400K drive (the 800K drive has internal speed 
control, or at least that motor speed line is not connected inside the 
drive). The 8 pin Apple 'sound IC' seems to be a filter and volume 
control. This, BTW, is based on me pulling a Mac+ apart and attacking it 
with a multimeter and logic analyser...

Any multiple voices must have been done in software.

-tony