Commodore PLA Replacement -- MOS 906114-01

$11.95
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SKU:
JSAS-PLA906114-01
Weight:
0.16 LBS

The PLA20V8 is a PLA that consists of two GAL20V8B chips from Lattice Semiconductor. The GAL is a programmable logic chip that looks a lot like the original PLA: It has an AND array, followed by an OR array. Depending on the mode of the GAL the signal then can go through a flip-flop, which the PLA does not have, but this flip-flop is bypassed in the so called "simple" and "complex" modes, which makes the chips rather close to a PLA, perhaps the closest possible chips to a PLA you can get. There are two GALs, because the logic will not fit in a single GAL.

EACH BOARD IS COMPLETELY ASSEMBLED, TESTED and READY FOR FREE IMMEDIATE SHIPMENT FROM THE USA!

 HOW GOOD IS IT?

 The PLA has 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 particular 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. Both PAL and NTSC tests have been done. No issues.

Does Epyx Fastload work?

Yes, it works fine. The Epyx Fast load cartridge is a rather questionable design that performs analog tricks on digital lines. In order for the Epyx Fast load 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 this GAL based PLA replacement.

 

READY FOR IMMEDIATE FREE SHIPMENT!!