• PDP-8 FPGA

    From Jeff@21:1/180 to All on Thu Jul 1 14:01:25 2021
    I'm working on an FPGA implementation of a PDP-8. Sure, it's been done before, but I'm having a go at it myself:
    https://youtu.be/cfQxtfuVsAA

    The front panel and RAM work, coordinated by a mock CPU module.

    Jeff.

    "For every complex problem there is an answer that is clear, simple, and wrong." -- H. L. Mencken, who indeed was a racist thereby proving himself right.

    --- Mystic BBS v1.12 A46 2020/08/26 (Raspberry Pi/32)
    * Origin: Cold War Computing BBS (21:1/180)
  • From Jeff@21:1/180 to All on Mon Jul 12 13:10:34 2021
    Well, this didn't all go according to plan...

    It turns out that the Mojo IO Shield is unsuitable for a front panel because
    it utilizes every sing available IO pin, leaving none for peripherals. So,
    I've had to make my own front panel. (http://coldwarcomputing.com/maximilian.jpg)

    I've decided to implement two independent PDP-8 cores on the same FPGA, each with its own mass storage, core memory, and two UARTs.

    I've also decided to use FRAM for the system memory, to mimic the
    non-volatile core memory of the original machines. Theoretically, it should
    be possible to unplug a running machine, plug it back in, and have it pick up right where it left off. This will slow it down significantly, but it should still be faster than the original hardware.

    The end goal of this project is to make a simple(?) PDP-8-based, FidoNet-capable, single-user-at-a-time BBS. That might be a bit more
    difficult than it sounds, because I'm not even sure Zip/Unzip were
    implemented on these machines and I'll probably have to do that from scratch. But that's why I decided on two cores: one to handle BBS stuff, and one to handle FidoNet stuff.

    Jeff.

    "For every complex problem there is an answer that is clear, simple, and wrong." -- H. L. Mencken, who indeed was a racist thereby proving himself right.

    --- Mystic BBS v1.12 A46 2020/08/26 (Raspberry Pi/32)
    * Origin: Cold War Computing BBS (21:1/180)
  • From Pepper@21:1/187 to Jeff on Fri Aug 20 23:44:29 2021
    On 01 Jul 2021, Jeff said the following...

    I'm working on an FPGA implementation of a PDP-8. Sure, it's been done before, but I'm having a go at it myself:

    Fun project! I run my BBS on the 'Obsolescence Guaranteed' PDP8/I. Well Ok, it's not using OS/8 ... it's on the same raspberryPI that runs the PDP8/I. But I do like the Blinkn' lights "working" away on the shelf :)

    -=Pepper=-

    --- Mystic BBS v1.12 A45 2020/02/18 (Raspberry Pi/32)
    * Origin: Cosmik Debris BBS (21:1/187)