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Message
From: "Kirill 'Big K' Katsnelson" <kkm@d...>
Date: Fri, 19 Sep 2003 23:53:42 -0700
Subject: [oc] Small CPU architectures
Guys,
I am wondering why, when FPGA allows one to have infinite varieties of
central (micro)processors, people keep implementing PIC, 8051 and
68K. First, I think that by implementing a task-specific instruction
set, one can end up with faster and smaller CPU.
I was looking for the subject, kind of research people do on "non-traditional"
if you allow me to put it this way, CPU cores. To my surprise, I found
practically no practical designs! I found a 4-bit micro with 4 different
instructions that fits into a Coolrunner, and a proof that the Turing machine
is implementable thus this is a general-purpose CPU... As far as going
both novel and practical, no luck!
For example, I *loved* the PDP-11 instructions set. When after VAXen there
arrived the first PC/XTs, I wondered what type of instruction set does that
8086 beast have. Oh my, I should not! When I found out, I was shocked by
its complexity and irregularity. It was disgusting! It was awful! After
a very regular PDP-11 instructions, seeing 8086 is not for the faint of
heart!
I think, for one, that it is one of the easiest-decodable CISC instruction
sets possible. I looked for an FPGA implementation; besides one sold as
a signle-board replacement for a PDP-11 (so it was the matter of necessity
and not choice in their case) I found none at all!
Anyway, it would be interesting to find out what kind of more or less
open research is being made in this direction.
-kkm
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