CPU design at the gate level

From: Richard Erlacher <edick_at_idcomm.com>
Date: Fri Sep 21 21:48:52 2001

A big part of this problem is that there is such a wide range of what is
collectively referred to as a processor. If you want to know how to design, at
the gate level, a set of registers, you start with how to build a flipflop and
go from there. If you want to consider the datapaths, you figure out what you
want in the way of multiplexers and tristate busses. The remainder is in how to
build a sufficiently fast ALU, and how to design an instruction set. Most
people start with the architecture, and that will dictate much of what's needed
in terms of registers and data steering logic. Concatenating the datapaths in
order to provide the necessary functions is not terribly difficult if the
instruction-set/architecture combination is regular and well-designed.

It's difficult to discuss in advance of a specific set of requirements, however,
because each case varies considerably.

I wouldn't be too hard on authors for not trying to do what can't be done well.

Specific examples are widely available in VHDL and Verilog examples on the WWW.
I find the VHDLs easier and quicker to understand than schematics, even though I
was raised on schematics.

----- Original Message -----
From: "Tony Duell" <ard_at_p850ug1.demon.co.uk>
To: <classiccmp_at_classiccmp.org>
Sent: Friday, September 21, 2001 7:35 PM
Subject: Re: CPU design at the gate level

> >
> > The book: "Computer Organization & Design, The Hardware/Software Interface",
> > by David A. Patterson and John L. Hennessy is a pretty thorough modern book.
> Yes, unfortunately it is a 'modern book'. I read some of Hennessy and
> Patterson once, and found it was great at telling me how to analyse a
> processor design, and optimise it, and things like that, but it didn't
> really tell me how to do the design in the first place.
> It seems to have been written for the modern 'engineer' -- the sort that
> couldn't design an engine (in the original meaning of 'ingenious
> mechanism') if his life depended on it. And as you might have guessed by
> now, I have little time for 'engineers' who can't design and build
> examples of the things they claim to understand.
> You couldn't take that book and learn enough to start wiring up gates and
> flip-flops to make a processor :-(
> -tony
Received on Fri Sep 21 2001 - 21:48:52 BST

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