70's computers
Noel Chiappa
jnc at mercury.lcs.mit.edu
Wed Oct 24 05:50:30 CDT 2018
> From: Paul Koning
> Some years ago I learned the architecture of the Dutch Electrologica X1
> and X8 machines. ... they gain a lot of efficiency by allowing almost
> all instructions to optionally set a condition flag, and almost all
> instructions to be executed conditionally on that flag. So a lot of
> code full of branches becomes much shorter. ... For example:
>
> if (x >= 0) { foo (); x += 2; }
> else x -= 3;
>
> translates to just 5 instructions:
Very clever!
What's the word length on that machine, BTW? I ask because it would be hard
to pull that trick on most short-word-length machines, there just isn't a
spare bit or two in the instruction to add that.
Noel
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