Re: Do we really need virtual machines?

In a sense we are all running on virtual machines all the time, even
when programming in C++ or Assembler. Until IBM introduced the System
360 in the 60's every computer was hardwired for its own instruction
set. The 360's were different: there were a number of
microprogrammable machines that all executed the 360 instruction
set. The trend since then has been to have a standard architecture and
instruction set that ranges over all sizes and speeds, but implemented
by different microprocessors running different microcode.


So the a better question might be: at what level do we want
compatibility?


(And, yes, there were nanomachines that were programmed to look like
micromachines, but you need to find someone like Sam Cohen to find out
about them.)


john slimick
slimick@pitt.edu
[Microprogramming was invented in about 1952, but it wasn't until the
1960s that ROMs got fast and cheap enough to make it practical. -John]

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