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Thread: MCL65+ 6502 Accelerator Board

  1. #1

    MCL65+ 6502 Accelerator Board

    Hi,

    I wanted to share my MCL65+ project which is a drop-in replacement and accelerator for the 6502 processor!

    The 6502 is emulated in software running on a Teensy4.1 which provides enough horsepower to emulate the CPU as well as the 6502 bus IO's. I also developed a small PCB which accepts the Teensy board as well as some buffers which allows it to be a drop-in replacement for the CPU. I have tested it so far with a VIC20 and next plan to try on an Apple II+.

    There is enough storage on the microcontroller to emulate expanded RAM and ROM for the VIC20 which I used to max-out the RAM as well as emulate a number of cartridge games. The MCL65+ can emulate RAM/ROM as either cycle accurate to the original 6502, or in an accelerated mode in which the computer is many times faster than the original processor! The 6502 core is cycle accurate to the original processor and even supports most of the undocumented opcodes which some applications require.

    The project files are available on GitHub and I have a number of of the boards that I can distribute for those who are interested. The boards use through-hole devices and the software is built using the Arduino GUI, so this project should be accessible to a wide range of users.

    Here are the project files: https://github.com/MicroCoreLabs/Pro...aster/MCL65%2B
    Here are some more details in my blog: https://microcorelabs.wordpress.com

    Thanks,
    -Ted Fried

  2. #2
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    Interesting
    While I didn't look into the details yet and I need to get some rest for tonight, will this work on Atari 130XE ?

  3. #3
    I have not tried the MCL65+ on this machine yet but I believe it should work.

  4. #4
    I just tried the MCL65+ on an Apple II+ and got some interesting results!

    https://microcorelabs.wordpress.com/...test-apple-ii/

    This project would not be possible without the Teensy 4.1's speed and memory capabilities. It is emulating both the 6502 processor core, bus interface signals, and all of the computer's RAM/ROM!

    The best part is that I was able to use the Arduino IDE to develop the software which really saved a lot of time and learning curve!

    I have a lot of experience developing FPGA-based processors... mainly micro sequencer-based ones... But when you have a 600Mhz+ microcontroller it opens your horizons to more software-based solutions, which are of course a lot easier to develop than RTL based ones!

  5. #5
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    I have not tried the MCL65+ on this machine yet but I believe it should work.
    Well 1985+ Atari 8-bit computers seem to be using 65C02 CPU code name Sally not to be confused with 6502C, Sally was a customized 6502 chip used in later Atari 8-bit computers.
    It has a HALT signal on pin 35 and a second R/W on pin 36 (these pin are not connected (N/C) on a standard 6502s). Pulling HALT low latches the clock, pausing the processor. This was used to sync the CPU with the video circuitry.

  6. #6
    I probably should have replied that the CPU is being emulated with a fast Teensy, so some small modifications could be made to emulate the Sally chip. A PCB update would be needed for the new pinout but otherwise it would be easy to port the design.

  7. #7
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    Is the github project files link broken I am getting 404 page not found ?

  8. #8
    Yes it is broken.. weird...

    Here's a link to this project: https://github.com/MicroCoreLabs/Pro...aster/MCL65%2B

    And here's a link to the top level for my projects: https://github.com/MicroCoreLabs/Projects

    Thanks,
    -Ted

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