Re: Can optimization-specific codes exist ?

"Chango Cho" <compusm@chollian.net> wrote:
>Can optimization-specific(only dedicated to optimization) codes exist?
>this question is generally related with the problems of
>'codification', I think. Environments that surround 'code' begin to
>change dramatically. I want to think about 'code' itself - as a
>turn-point.


Digital's PDPs used to allow custom opcodes to be defined which could
then be included in programs. I don't recall whether it was also
allowed by VAXen. Motorola had a version of the 68000 that allowed
modification of the microcode [but not the nanocode].


In any case you would need a microcoded CPU with a writable store and
an "escape" feature to direct execution to the extensions. Modern
RISCs still use a horizontal microcode [mostly], but I'm not aware of
any that allow field modification of the program. I wouldn't want to
try it even if they did.


Some of the available DSP cores include both a RISC CPU and an FPGA
which could be used to extend the CPUs functions, but the ones I have
seen so far have integer only CPUs and the included FPGAs are too
small to help with floating point math - no good for general purpose
computing. However, DSPs are evolving very rapidly so my information
may be out of date.


George Neuner
Dynamic Resolutions, Inc.
[I believe that by "codes" he meant parts of programs, not computer op-codes.
In any event, the only PDP I can think of that was user microprogrammable
was the not terribly popular PDP-11/60 and as far as I can tell, the only
thing that people did with it was some DSP stuff. -John]

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