The Lisp Machine

[P. T. Withington]

On 4/4/98 16:08, David Gadbois wrote:

>   Date: Fri, 3 Apr 1998 19:27:53 -0500
>   From: "P. T. Withington" <ptw@pobox.com>
>
>   I've put two old (unpublished, until now) papers, "The Lisp
>   Machine:  Noble Experiment or Fabulous Failure?", and "The
>   Symbolics Virtual Lisp Machine (extended abstract)", which might be
>   amusing to this group, at <http://www.pobox.com/~ptw>.
>
>Wow, great papers!  Any chance of ever seeing the full VLM paper?
>
>It occurs to me that there may be a couple of alternatives to doing
>the emulator in assembly.  (This may have relevance if the MIT lispm
>sources ever get released.)  Clearly, if performance permits, it would
>be better to do an emulator in a high-level language so as to allow
>portability and to take advantage of new implementations that have
>difference optimization characteristics:  larger, differently mapped
>caches, more functional units, register renaming, etc.
>
>1. Reschedule the output of the compiler to better take advantage of
>the chip's instruction issue regime, and move stuff around (using
>knowledge of the code) to get better instruction cache behavior.
>
>2. Fix the compiler to do the right thing.
>
>Were these (and perhaps other) approaches rejected because doing it by
>hand made a big enough difference, or was it a time-to-market thing?

Strictly time-to-market.  We didn't have time to build or wait for better 
compilers.  The program to build the VLM was a last ditch effort to save 
the company.  It exceeded our expectations, but it was not enough to 
overcome the outstanding debts.