Commodore 64 (was "Re: Teaching kids about computers...")

Roy J. Tellason rtellason at
Tue Nov 27 11:27:10 CST 2007

On Monday 26 November 2007 23:17, Ensor wrote:
> Hi,
>   >> Also, full schematic diagrams for the machine were included
>   >>in the "Programmer's Reference Guide".
>   >
>   > For one version of it,  yeah. There were at least four different
>   >versions of the boards out there....
> Good point.
> But I still feel that the schematic which was published would be a useful
> learning aid despite this. It would only make a difference if you were
> going to hack around inside the machine itseelf, which may or may not be an
> issue.

True.  Giving the details of what was connected to all of the connectors was a 
lot of what was useful about it.

>   >....Another was RAM, the later boards used two 64Kx4 parts instead
>   >of eight 64Kx1, and the very latest ones I saw combined two of the
>   >ROMs (Kernel and BASIC?) into one single chip.
> I'd assumed that all 64Cs had the combined Kernel/BASIC ROM, was this not
> the case?
> Likewise, I was under the impression that the move to a pair of 64K*4 DRAMs
> also came about with the advent of the C-64C....

Not really,  though it was more often the case than not.  The major difference 
between those new cases and the old was the difference in the way the 
keyboard was mounted.  The old-style cases had eight screws holding the 
keyboard to the top of the case,  while the newer ones had the keyboard 
mounted to the bottom half,  over some metal support brackets.  If you had a 
new case and wanted that style but wanted to use your old parts otherwise,  
you'd need those brackets.  And they were different for a couple of different 
form factors-- the later boards with higher density were narrower,  
front-to-back,  than the older ones were.

Now that I'm thinking about it a bit further, I  also have this vague 
recollection of them combining the PLA chip with a bunch of the glue TTL and 
making it even simpler yet,  though since the PLA was a common failure part 
it made it more difficult to repair.

Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin

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