If you are a little familiar with the hardware of the Commodore 64 you know that the PLA chip in the Commodore 64 is perhaps the most failing chip of the entire Commodore 64 today.
You will find references to these chips under the following references 906114-01, 251064-01 and the 82S100.
This PLA (Programmable Logic Array) is the custom chip that manages the memory map and memory bank switching.
Especially the chips that were produced in the years 1983 and 1984 suffer a lot from failure.
I once read somewhere that the chemical process that was used at the time to produce the chips, the main reason is that they now fall out (failed) in masses
The PLA and its modern Replacements
Since the MOS factories are long gone and there is no manufacturer that can still produce this technology, the community has been searching diligently for a way to replicate / emulate the workings of the logic that makes up this chip.
There are replacements based on a simple Eprom, there are replacements that use a high-end CLPD, each solution has its advantages and disadvantages.
One solution is a poorly (partly) functioning replacement that is said to destroy the entire Commodore 64 in the long term, the other solution is multifunctional, but then again has miniature islands and must be provided per machine / revision of (miniature) solder bridges.
and then there's the brainchild of Daniël Mantione, who came up with a different approach for the PLA Replacement based on GAL chips.
And that approach, according to all kinds of tests, resulted in the 'most compatible' PLA replacement, without any known drawbacks.
In fact, it's so compatible that there's no need to do anything for any revision of the C64.
it has rightly proved to be a Drop-in replacement for all systems equipped with this PLA.
And with that it is THE replacement that has made the heart of many C64 (Lovers) beat faster🙂
Frequently Asked Questions :
Does Epyx Fastload work with PLA20V8
Yes, this one works fine.
Does the PLA20V8 work in all C64 motherboards?
Yes, except for the shortboard, it uses a different kind of chip.
Can I also use alternative kernals with the PLA20V8 ?
Does Super-Zaxxon work with the PLA20V8
Is it already available?
Commodore 64 GAL PLA Close-up