The PLA (MOS 906114-1) is a crucial chip in the C64 and it is also one of the most common points of failure. Without it, nothing works.

Old stock is expensive, fairly hard to come by and just as reliable as the part you are replacing.

The original PLA chip is a relict of the 70s and the MOS implementation of it is particularly prone to failure. The PLA20V8, aka GAL-PLA is based on GAL20V8B EEPROMs and is a drop-in replacement for the original. If the original chip is socketed, there is no soldering required, just replace the old chip with the new one and you're back in business. If the old chip is soldered into the motherboard, you need to unsolder the old one and either solder the replacement in or, as I would recommend, solder in a suitable socket.

This device is for the C64 long boards (Assy 250407, 250425, 250466). It has not been tested with the first series boards and will definitely not work in the short boards (Assy 250469) as they use a completely different chip.

This replacement was originally designed by Daniël Mantione.