[vcf-midatlantic] Original Macintosh Architecture Questions

Dean Notarnicola dnotarnicola at gmail.com
Wed Jun 23 21:04:58 UTC 2021


The original Mac's architecture locked out the CPU's access to memory
during screen refreshes, so maybe that changed in the Classic (which also
used a 68000)

As far as sound, according to Wikipedia:

Two TTL chips provide an 8-bit P
<https://en.wikipedia.org/wiki/Pulse-width_modulation>WM sound driver
(74LS161 type). So it could do 8-bit samples.
Two analog chips providing sound amplification (MC14016 switch, LF353
op-amp)

You would clock the sound using the 6522 VIA bridge chip that is connected
to the RTC and a 32.768 oscillator

On Wed, Jun 23, 2021 at 4:35 PM Bill Degnan via vcf-midatlantic <
vcf-midatlantic at lists.vcfed.org> wrote:

> John,
> If they used a 60040 rather than a 60000 chip that would be a lot faster
> Bill
>
> On Wed, Jun 23, 2021 at 4:25 PM John Heritage via vcf-midatlantic <
> vcf-midatlantic at lists.vcfed.org> wrote:
>
> > Hey folks --
> >
> > Two items I'm curious about on the classic (and very original) Apple
> Macs..
> >
> > 1.  Mac (128kb ,512kb, etc) audio -- was there a custom or off the shelf
> > sound chip for the audio on the original Mac?  and was it 1 channel / and
> > was it a custom chip by Apple?  (how did it achieve speech synthesis in
> > 1984)
> >
> > 2.  The Macintosh Classic released in 1990 "was about 25% faster than the
> > original Macs".  This is in line with the Atari ST often being quoted as
> > faster than a Mac when emulating a Mac via Magic Sac or similar.  What
> > changed in the architecture to make the Mac Classic (or an ST in
> emulation)
> > faster than the original Mac?  Was it faster memory that gave more
> > availability for CPU usage?  were only certain instructions sped up or
> was
> > everything faster?
> >
> > Thanks!
> >
>


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