LispOS on a 68000

David Tillman
Thu, 14 May 1998 16:46:21 -0500

>>>>> Mike McDonald <> writes:

>   Wow! I haven't heard of anyone trying to hack a homebrewed
> system in years! Everyone seems to just buy an already built
> motherboard (most likely, a PC one) and then hack
> software. Sounds like fun. (Really sounds like things from my
> past. Say fifteens years ago! Anyone remeber a thing called the
> "Big Board"?) Are you building your own MB to learn how or
> what?

    I never used a big board, I did have a brief love affair
    with CP/M in my teens. No, I'm not building one to learn
    how, I already know how (or did). Of course, that was back
    when the 6809 was hot. At the moment I am sick of the constant
    MHz race in processors and would like an architecture that
    does the Right Thing.

>   The 68030 would probably be nicer because of the MMU. Having
> a MMU under your control can be useful for things like garbage
> collection.

    I also noticed that there is a public domain 68030 mother
    board design floating around. You can apparently buy the
    blank boards. However, I would have no qualms about running
    the photoplots through a board house. This board is designed
    to be compatible with ISA cards, an interesting feature (bug
    as I see it).

    On the down side, Motorola has issued a End of Life statement
    for the normal 68030. The 68EC030 continues to be supported
    but lacks the MMU (why?). I haven't checked the other variants
    for MMU suport. Of course, you could tack on a 68332 MMU unit...

>> Thoughts? Has this road been covered before? I would probably
>> just communicate with it by way of serial at first; a nice
>> bitmapped display wouldn't be too hard though.

>   Oh, we've yacked about the same type of thing for over a year
> now and some 2000+ messages! :-) We've been assuming the use of
> a standard PC as the machine though. Everything else has been
> an endless argument.

    Yes, I remember some of the circular discussions on the list.

    Something this hardware-centric may be a bit off-topic for
    the LispOS list. If anyone wants to discuss it further, I
    would be glad to discuss it here, or I can start a lisp-hardware

    I think my goals would be:

        a. Have *one* variant of video board.
        b. Have *one* variant of I/O board.
        c. Use standard SIMMs.
        d. Use SCSI as much as possible.

    I realize that using a 40 MHz processor may seem like a giant
    step back. The problem is, newer, faster processors are just
    to finicky to diddle with on a one off basis. Otherwise I would
    be looking at the PowerPC or an Alpha.