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Andre' Fachat's micro-PET (2020-2021)


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Spurred to action by the Mini-PET.  He uses a 65816 as the CPU, and a CPLD to do a lot of the dirty work on the board.


  • Commodore 3032 / 4032 / 8032 / 8296 with options menu to select at boot
    • Boot-menu to select different PET versions to run
    • 40 col character display
    • 80 col character display
    • 8296 memory map emulation
    • IEEE488 interface (card edge)
    • Tape connector (card edge)
    • PET graphics keyboard, or alternatively a C64 keyboard
  • Improved system design:
    • 512k video RAM, 512k fast RAM accessible using banks on the W65816 CPU
    • boot from an SPI Flash ROM
    • up to 12.5 MHz mode (via configuration register)
    • VGA b/w video output
    • Write protection for the PET ROMs once copied to RAM
    • lower 32k RAM mappable from all of the 512k fast RAM
  • Improved Video output:
    • Hires graphics mode (using a configuration register)
    • modifyable character set
    • 40/80 column display switchable
    • 25/50 rows display switch
    • multiple video pages mappable to $8000 video mem address



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On 9/28/2021 at 5:34 PM, Kalvan said:

For a real improvement, he could have used his 65000 series project for the CPU...

Was that ever realized in a functional design? The page says it wasn't. Also, the uPET site talks about only using parts available as new this year. That would not preclude a 65k if the HDL existed, as FPGA is available today... just thinking out loud.

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On 9/28/2021 at 7:01 PM, Scott Robison said:

"To build the board, you have to find a provider that builds PCBs from Eagle .brd files. Currently no gerbers are provided."

Too bad PNG wasn't used... 😉

His README suggests that, however there is a Gerber folder under 'Board' that appears to have a full set of files.  (I'll probably get around to cloning the repo this weekend and see how much it costs... maybe I'll buy 5 must for fun). Anyone?

Also, PCBway (hate to even mention the word) offer an Eagle -> Gerber single click convert utility built into their site (or used to).  Haven't tried it.


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So reading his webpage a bit, it seems that CPLDs are most useful for all the glue hardware -- logic gates, for instance, that do some address decoding.  He uses a 65816 of course for the CPU. 

Meanwhile, Frank shows us how FPGAs are suited for the raw capability of processor design, be it graphics, sound, or CPU.

That leaves RAM, ROM, and I/O.



Edited by rje
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