Electronics > Projects, Designs, and Technical Stuff

Cloning a Commodore PET-2001

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GK:

--- Quote from: CJay on July 15, 2017, 07:52:05 am ---Awhh damnit, shame you're so far away, I've got a few lovely keyboards that have proper keyswitches and would be easily adaptable for this, they weigh a ton and would cost a small fortune to post.

Very impressive project though, I harbour a bit of a desire to build one (but realistically it'll probably never happen)

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Well darn,  that's annoying. An old keyboard to quickly hack would be quite handy right now so that I could give Lunar Lander a whirl  :D

GK:

--- Quote from: SeanB on July 15, 2017, 02:25:59 pm ---If keyboard decoding simply use the fact that a keyboard is slow, and use the micro to drive a crosspoint switch ( or at least a simple one using a pair of CMOS analogue switches to emulate one) that will emulate the key being pressed. As you likely will also have a shift and function modifier key as well simply use another analogue switch, and isolating diodes,  to do the functions, thus emulating the keyboard using a simpler to interface PS/2 keyboard decoder and a slower micro that only has to set the analogue switch inputs and outputs at a human type rate.

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Yep; I actually considered doing essentially this for a second in 74HC logic, but unfortunately it turns out to require a great deal of logic. The gates need not be analogue-switches though (AND gates with the output ORed as per the matrix are fine) which makes the whole thing trivial to implement in a small CPLD, which is what I am about to start right now.

GK:
I think I'm getting the old-school computer bug. Sifted through my stash of DIP pulls from salvaged digital (computer, etc) boards this morning. Do I have anything particularly exciting here?

GK:
OMG! The "MBL8088-2" (center-bottom) is an 8 MHz version of the classic Intel MPU as used in the 1st IBM PC. This might be the perfect part for an Altair work-alike on steroids.

chickenHeadKnob:

--- Quote from: GK on July 16, 2017, 04:12:05 am ---OMG! The "MBL8088-2" (center-bottom) is an 8 MHz version of the classic Intel MPU as used in the 1st IBM PC. This might be the perfect part for an Altair work-alike on steroids.

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Get an xt motherboard and a NEC v20 chip instead and be able to run both MS-dos and CPM.  For a brief time I had to use such a machine to support legacy CPM based software. It ran seamlessly, a bit better than a real z80/8080 machine.

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