The Commodore 64 is a computer that refuses to die and decades after its introduction, its community is still going strong. Many computers still work fine, in contrast to generations of computers that came after it, and died too soon, Commodore 64 hardware is often in good shape. But that doesn't mean that these computers never fail, and repairing them is a common activity in the community. If you work with Commodore 64 hardware, you will know that a broken PLA is one of the most common defects. Especially PLAs that were produced in the years 1983 and 1984.

How good is it? This PLA has until now passed everything thrown at it. Meanwhile, a lot of C64 boards have been tested, with perfect results and a lot of C64 software and cartridges have been tested.

Does Super-Zaxxon work? Yes, it does work perfectly! Super-Zaxxon switches banks by means of accesses to the address lines of the C64 and as such, noise on the C64 address lines can cause undesired bank switches. This is a particuler concern for EPROMs, which are known to cause switching noises on address changes. The way the GAL20V8 works, with and AND array and an OR array just like the original PLA, this kind of noise is not expected and indeed, the cartridge works perfectly.

Can I use an alternate KERNAL? Yes! An alternate KERNAL cartridge is a real PLA torture, because a KERNAL cartridge changes the C64 mode two times within a half cycle and thus likes a responsive PLA. This has been tested both with the 1541 Ultimate II and with the Easyflash 3 and works perfectly.

Does it work in all C64 mainboards? Yes, except for the short board assy 250469 of course, because it uses a completely different type of chip. Assy 326298, 250407, 250425, 250466, 251103 (SX64) and C64 Reloaded MK1 have been tested. Assy 250441 and KU-14194HB have not been tested yet, but from what I know about these boards, I am confident about compatibility. Both PAL and NTSC tests have been done.

Does Epyx Fastload work? Yes, it works fine. The Epyx Fastload cartridge is a rather questionable design that performs analog tricks on digital lines. In order for the Epyx Fastload to work, a PLA needs to have similar analog properties and be stable at the border voltage between 0 and 1. This is the case for the GAL20V8B.