Whoops, I did it again! VIC-20 on the way...

[rubber_jonnie]

Looks similar to this: http://www.sdiy.org/richardc64/vic20/vic01.html

It does.

Hmm, I have the 2 prong PSU connector, so it seems like it's an earlier one, mine seems to have 11 2114 RAM ICs.

[stephen_usher]

OK, looking at what that's doing... One lead goes off to D2 on the VIC chip, with a NOR gate with something else, which is then flipped by the '04 and fed into the RAM /WE line.

So, I'm guessing that if a write is done to a specific address with D2 high then it doesn't get written to RAM. This suggests that whoever did this had a peripheral which sat somewhere and was controlled by a write to that address.

[rubber_jonnie]

OK, looking at what that's doing... One lead goes off to D2 on the VIC chip, with a NOR gate with something else, which is then flipped by the '04 and fed into the RAM /WE line.

So, I'm guessing that if a write is done to a specific address with D2 high then it doesn't get written to RAM. This suggests that whoever did this had a peripheral which sat somewhere and was controlled by a write to that address.

Sadly no peripherals that are obvious, or other internal mods. Interestingly, there is a wire that goes off to the CPU, pin 4 which is IRQ. Might try and fully reverse engineer the thing based on the wiring.

[stephen_usher]

Oh, that's the CPU, I thought it was the VIC chip.

[rubber_jonnie]

Oh, that's the CPU, I thought it was the VIC chip.

Yep, the VIC is in the 'boxed' area behind the video and IEC connector for the floppy.

[BennehBoy]

I can't believe how clean that VIC is, nice find.

You may find this interesting:

[rubber_jonnie]

I can't believe how clean that VIC is, nice find.

You may find this interesting:

Yeah, I was a little shocked, it even still had the cardboard shielding inside :)

As for that vid, I watched it the other night :) Definitely a good bit of Commodore history.

[rubber_jonnie]

Well, I did something crazy tonight. I saved a program to cassette and loaded it back!!!

Here we are loading:

IMG_20220216_205757.jpg

And again after running my simple 2 liner:

IMG_20220216_205831.jpg

I already had the cassette deck with my C64, but it works a treat. Also came up lovely after a scrub with a magic sponge and a plastic wipe :)

Aren't the on screen letters HUUUUUUUUUUUGGGGGEEEE.

[stephen_usher]

Wow! Cassette loading? What will they think of next. Hehe.

[rubber_jonnie]

Wow! Cassette loading? What will they think of next. Hehe.

I know right, it's amazing!!