LispOS on a 68000

[Mike McDonald]

>From lispos-request@math.gatech.edu  Thu May 14 12:18:04 1998
>Resent-Date: Thu, 14 May 1998 14:46:43 -0400 (EDT)
>Date: Thu, 14 May 1998 13:47:32 -0500
>From: David Tillman <dtillman@cannonexpress.com>
>To: lispos@math.gatech.edu
>Subject: LispOS on a 68000
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>    How feasible would a Lisp/Scheme OS be on a 68000?
>
>    Please realize that I am in question-asking-mode here. I have no
>    idea how Lisp internals are implemented. I am thinking about putting
>    together a homebrew 68000 or 68030 and it would be nice to run
>    something besides Forth on it. My concerns are:

  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?

>        a. Speed - If I wirewrap it, I will be stuck to around 8-10MHz.
>           Not exactly blazing. If I use a 68030, I will probably knock
>           out a couple PCBs for it and speed won't be quite so much an
>           issue.

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

>        b. Implementation - I don't know enough about Lisp to actually make
>           my own (not a pretty one, anyway). I could probably hack together
>           some Lisp/Scheme looking thing, but that wouldn't be quite the same.

  Nah, it'd be BETTER! If you're going to build your own machine, why
make it look like everyone else's? I was thinking that CMUCL might be
a good base to start with but I don't think it has ever been ported to
the 68Ks. Seems like it should be doable though. One thing that would
be nice is support for multiple processes (aka threads). Then you
could eventually have things like network deamons running in the
background. Hmm, if the CADR code is ever found, that'd make an
interesting base to work with. (In case you don't know, the CADR was a
lisp machine built by MIT years ago. Same basic class of machine as
you're talking about but built specificly to run lisp.)

>    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.
>
>    -Dave

  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.

  Have fun and don't be afraid to go your own way!

  Mike McDonald
  mikemac@mikemac.com