Re: Commodore and Apple

[Jim Butterfield <fjb@pathcom.com>]

On Sat, 05 Mar 2005 13:29:26 GMT, jimbo@radiks.net (Jim Lawless)
wrote:

>On 04 Mar 2005 23:48:25 -0800, Eric Smith <eric@brouhaha.com> wrote:
>
>>The PET did use only off-the-shelf components.  The only custom
>>electronic components in either the Apple II or the PET were the
>>masked ROMs.

The RAMs were a special Commodore brew (was it 6552?) that Commodore
claimed were part static, part dynamic.  Many users who wanted to
replace or expand memory had a hard time getting these, and I recall
there were quite a few pin-swapping adapters around to allow more
readily available memory chips to be fitted.

But that's a long time back.  Maybe the earliest ones were arrays of
simple static rams, similar to those used in the KIM-1 (2102?).  I
recall that dual access to RAM (processor, video) was accomplished by
an even-phase / odd-phase scheme.

>I'm curious: Was the design of the early PET computers similar to the
>design of the KIM-1 ?

Not much, in my opinion. I see the KIM-1 as a collection of
demonstration interfaces, intended for micro board designers to adapt
to their own systems:  teletype interface, audio output via
bit-banger, audio input via PLA, keyboard interface, LED display
interface.  My guess is that MOS Technology thought that their market
was design engineers who would test out the capabilities of the 6502
and its support chips, and then design their own boards.

They were astounded to see it become a popular hobbyist machine, I
think.

		--Jim Butterfield

Hmmm.  Can't just sign as "Jim B" any more.  That Brain guy is making
off with my abbreviations ...  <g>



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