First gen 2001-8?

[mengstr]

Nice project! I'll give it a go when I get back home tonight and see what speed I gen on my Macbook M1. If I remember correctly my Digital project that simulates a 8080 machine (including a gate simulation of the CPU itself) also ran about 1% of the original speed - but still immensely cool to be able to boot up cpm using a simulated floppy and run applications.

I've recently bought an original chiclet PET 2001-8 in a quite a bad shape, that's the one with the horrible static rams which probably 90% of them are broken. I definitely have a lot of work ahead of me this summer. So a proper simulation of if would be great :-)

[innot]

Hi Mats,

thank you for your comment.

And I envy you for getting your hands on an original chiclet PET 2001 😁

I took a look at the schematics and I do see some similarities to my simulated CBM3032. The video circuitry seems very similar, although drawn differently. The RAM interface is of course much simpler without any refresh circuitry and no RAS/CAS address multiplexing.

Unfortunately I do need to work on some other projects now, so won't be able to invest time into making a simulation of the original PET.
Maybe in a month or two...

[mengstr]

I might give the 2001-8 adaption a go myself this summer. I don't particularly enjoy Java, but you've already taken card of that part so it's only "simple" digital logic stuff so.....

But you should not be too envious of my PET... The former owner mutilated it and hacksawed the case a bit, removed the datassette and just patched in a newer model full size PET keyboard. So it's really a franken-pet. I consider the chance of getting a new chiclet keyboard and a datasette for a reasonable cost is next to impossible. So I will just clean up his metalworks for the exterior and fix a bunch of his horrible PCB repairs/fixes/improvements. But I can't complain for just $250 I have myself a full summers worth of fixing ;-)

[innot]

Oh dear, that poor thing looks like a lot of work...

BTW, I noticed that the CRT looks rather greenish. AFAIK the first gen PETs with the chicklet keyboard all had white phosphor CRTs, so maybe the screen got transplanted as well.

Did you check the main PCB? What RAM and ROM chips does it have?

ROM: 6540 or 2316?
RAM: 6550 or 2114?

I once again procrastinated my other projects and have started to implement the original PET in Digital.
Currently about 60% done, video is already working, but I do get constant short circuits on the bidirectional data lines when running the CPU.

This might be due to the missing ROMs and RAMs which are not yet implemented.

If you can give me the your Board ASSY number, I can base my simulator on that. Should be either:
320008,
320081,
320132, or
320137

At least that are the versions I have found

Also, have you gotten around to trying the simulator yourself? I am curious if it works on machines other than mine.

[innot]

Yes, it is about twice as fast because it only has to simulate 8 system cycles for every CPU clock cycle. And during bootup it only has to check 4k of RAM instead of 16k, so getting to the READY. prompt should be 8 times faster.

I have everything wrapped up, the branch has been merged into main and there is a new release 3.

This also includes simulations of the original Commodore Diagnostic Clip and User Port/Keyboard diagnostic dongles. Maybe this can be helpful when restoring your PET.

P.S. I was curious about the current price for PETs on ebay --- and to my surprise found an original PET in good condition locally for a reasonable price with no offers yet.
That I could not resist and now a PET lives in my home 😁
It is supposed to be non-functional (I haven't checked) but that - I guess - is to be expected with an 320008 board.

[mengstr]

Cool that you found one locally at a reasonable price. Hopefully you will have at least a bit of repair to do on it or else it'd be a bit boring ;-).

I can't wait to start my repair this summer, but I'm not looking forward to the metalworks I have to do to pretty up the keyboard situation. Luckily the condos I live in got a small "hobby room" in the basement with some tools and a workbench. Maybe we'll end up being "repair buddies" this summer getting our machines in shape. ^__^

[brmarkus]

Just recently I watched "https://www.youtube.com/watch?v=uHbhH7ISL_Y" which is specifically about PET's keyboard - and finally adding a specific paste to the key's "carbon pads".

[innot]

Cool that you found one locally at a reasonable price. Hopefully you will have at least a bit of repair to do on it or else it'd be a bit boring ;-).

Well, it was sold as "not working", so there will be some repairs...

All of the 6550 RAM Chips have heatsinks mounted on them, so I am a little bit hopeful that they might have survived. I also noted, while all other chips are of 1978 vintage there is one TTL chip from 1993, so it has been restored before and was probably running in the 1990s

But I have shelved the PET for the moment (without powering it up) to get some other projects done. Maybe later this year...

I can't wait to start my repair this summer, but I'm not looking forward to the metalworks I have to do to pretty up the keyboard situation. Luckily the condos I live in got a small "hobby room" in the basement with some tools and a workbench. Maybe we'll end up being "repair buddies" this summer getting our machines in shape. ^__^

Metalwork would be outside my comfort zone as well. I am mostly a software guy that is trying to become more proficient in hardware, especially electronics.

[innot]

Just recently I watched "https://www.youtube.com/watch?v=uHbhH7ISL_Y" which is specifically about PET's keyboard - and finally adding a specific paste to the key's "carbon pads".

Yes, it is a good thing that the PET is popular enough that there are a plenty repair videos on youtube. WRT the keyboard - we'll see if anything is required. Watching some other repair video it seems that my calculator style keyboard has slightly different (wider) contact points than 8-bit-guys full size keyboard.