OK, allow me to try again, this time with the errors corrected. (Hint: Never
send emails to the PICLIST late at night on Percodet!!)

Douglas Wood
Software Engineer
dbwood@kc.rr.com
ICQ#: 143841506

Home of the EPICIS Development System for the PIC
http://epicis.piclist.com

What is the goal of the ALU control? To 1) conserve power or 2) to insure
that the ALU gives up the answer within a fixed time?

As Olin has pointed out, the power issue is probably not really much of an
issue (depending, of course, upon the technology used to implement the ALU
and the entire CPU). As for point #2, you are most likely building a
synchronous system, in which case there are a lot more to it than simply
controlling the coming and goings of the ALU; otherwise you're building an
asynchronous systems, in which case the ALU ON/OFF control is the least of
your worries.

If you're controlling the ALU simply because you don't like the idea of
"messy" outputs FROM the ALU due to "messy" inputs TO the ALU, you probably
are not building much of a CPU. There's a lot more to CPU design than the
ALU.

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