Nice try Commodore...

[MicroCoreLabs]

 

[Eudimorphodon]

Did you replace 4108’s in the other bank with that mixed bag of 4116’s, or did it come that way?

(I have one of those drilled boards that *had* 8K of 4108’s in the other bank but like three of them were bad. A friend decided to replace them with 4164s (did a very nice stealth job disabling the 12v and -5v lines) and changed the jumpers so it sees 16K now, I’ve been thinking of using a GAL to make it a stealth 32K machine, IE, leaving the drilled bank unmolested.)

 

[MicroCoreLabs]

I received it this way. It is badged as a 4016 and when I opened it I was not surprised to see a second bank of DRAMs. I just thought "Cool, someone upgraded it.". Then I moved on to fixing the keyboard.

Later on I was looking at the ROMs and my eye caught the holes in the PCB under some of the DRAMs. I looked a little closer and through the holes I could see some wires under the motherboard.

I smiled and thought to myself, "Good for you previous owner! Stick it to Commodore and not let them get in the way of you upgrading your machine!"

I'll bet these drill holes discouraged the majority of users from upgrading their 4016's to 4032's but I'm glad to see that at least this person was not deterred and did it anyway.

 

[MicroCoreLabs]

Many of this PET's keys did not work, so I pulled the all of the rubber contacts, bathed them in soapy water, and wiped the conductive material with an alcohol-dipped Q-tip. I also cleaned the PCB key contacts with soapy water and lightly wiped them with a Magic Sponge. This method seems to work well as all keys are all functional - at least for now.

 

[MicroCoreLabs]

I dont have a cassette player or a disk drive. so I think I will give the MCL65+ 6502 drop-in emulator a try. I would like to see if it works in a Commodore PET an maybe try some acceleration. It would be amusing to have it become the World's Fastest Commodore PET

There are a few other more practical things I would like to try:
- The MCL65 can mirror motherboard RAM and ROM in the Teensy's internal memory which I could use to swap various diagnostic and other ROMs.
- I *believe* that if I load a .PRG file's binary into the Teensy's emulated memory array I can just SYSxxxx in BASIC to run it. This could be a simple way to side-step needing a disk drive. I just convert the binary to a text C code array and compile it with the MCL65+ code.
- Because the MCL65 replaces the 6502 at the socket, in theory I can run diagnostic programs (using C code.) which test and probe motherboard resources at the 6502's bus interface.
- The MCL65+ uses a Teensy 4.1 which has a MicroSD connector, so at the same time it is emulating the 6502 it could also provide IEEE 488 access to the MicroSD to act as a disk drive. It could intercept accesses to the IEEE 488 motherboard support chips and handle it all within the MCL65+.

 

[Hugo Holden]

I came up with some ideas to fix that Commodore pcb vanadalism. One was to make a very thin pcb that would overly the damaged connections, effectively making the original pcb 4 layer. It would be a rectangle of pcb, that sat on the pcb top. To make the repair even more attractive, just a very thin top & bottom pcb overlay, that would re-establish the cut connections and hide the ugly holes on both sides of the pcb into the bargain.

 

[MicroCoreLabs]

That would be an attractive and potentially a practical fix. I wonder if the stubs and wires are degrading signal integrity. A separate board with some stub trace cuts might yield a better result.

 

[snuci]

If I had one of those "Swiss cheese" 4016s, I would leave it as is. I think it's far more fascinating with the holes and patches but that's just one guy's opinion.

 

[ClassicHasClass]

It's certainly notable for the historical value.

 

[Eudimorphodon]

If I had one of those "Swiss cheese" 4016s, I would leave it as is. I think it's far more fascinating with the holes and patches but that's just one guy's opinion.

This is why I'm kicking around that "stealth" idea with enabling fuller usage of the 4164s in the complete bank. The "holes drilled in the motherboard" thing is a pretty notable piece of Commodore lore, I didn't know if I actually believed it until I saw it in person, so I definitely would never cover it up.

(On the flip side, it's not surprising that back in the day those holes didn't actually stop someone from populating the bank anyway. They actually really blew it with where they stuck the holes on that board, it's trivial to bridge over them when they're placed like that. I want to say I think they put one of the holes in a slightly more devious place on mine, but I don't have it in front of me.)

 

[MicroCoreLabs]

If I had one of those "Swiss cheese" 4016s, I would leave it as is. I think it's far more fascinating with the holes and patches but that's just one guy's opinion.

The "holes drilled in the motherboard" thing is a pretty notable piece of Commodore lore, I didn't know if I actually believed it until I saw it in person, so I definitely would never cover it up.

I agree - The holes are historically interesting.

This is why I'm kicking around that "stealth" idea with enabling fuller usage of the 4164s in the complete bank.

If one wanted to provide 64 KB on a drilled motherboard then the MCL65+ could be used to provide al of it without any modifications to the motherboard.

 

[Eudimorphodon]

If one wanted to provide 64 KB on a drilled motherboard then the MCL65+ could be used to provide al of it without any modifications to the motherboard.

So could a daughterboard under the cpu, or something hung off the expansion header. So what’s the point?

 

[MicroCoreLabs]

So what’s the point?

I dont follow...

 

[Eudimorphodon]

I dont follow...

Just pointing out that there are plenty of alternatives for making a 16 K PET into a 32K one that don’t specifically require replacing the 6502 with an emulator. A MCL65+ is no more “stealth” than a PETVET, Romulator, Tynemouth ROM/RAM, or any number of other piggyback boards.