Denial

I have a partially failing VIA UAB1. I observed that left shift & WEASZ don't print the symbols, only the letters. Right shift works fine. Bizarre. I am thinking I can live with it, or wondering what this partial failure could give when I swap UAB1 & UA3 instead.

IMHO, the VIA is probably the easiest chip to replace in a VIC-1540/VIC-1541/VIC-20. Many people sell them for peanuts.

I tested the W65C22N circuit which was specially adapted for full compatibility with old NMOS chips (IRQ sharing) and they work perfectly fine as a drop-in replacement to the MOS 6522. They consume less than 1/10th the power of the original chips too and they're inexpensive.

I think this is the only 65XX series chip we can safely say is effectively still in production.

If I have any problem with a VIA, the trashcan is my 1st option.

Added edit: The W65C02S is still in production but there are instruction set differences and hardware differences which prevents it from being called a direct drop-in replacement to the MOS 6502.

I have plenty of rockwell 6522 replacements. But on a 9vAC 1982 machine I prefer the thought of a partial failure rather than a replacement. Just my opinion.

mrr19121970 wrote:I have plenty of rockwell 6522 replacements. But on a 9vAC 1982 machine I prefer the thought of a partial failure rather than a replacement. Just my opinion.

If collector's value is important, I'm quite sure its possible to find replacement MOS 6522 that are also dated 1982. I sure have a good bunch of them.

Then it won't look as if anything had changed inside the machine.