Re: [Caml-list] More registers in modern day CPUs

[Richard Jones <rich@annexia.org>]

On Thu, Sep 06, 2007 at 10:55:20AM -0400, Chris King wrote:
> On 9/6/07, Tom <tom.primozic@gmail.com> wrote:
> > However, would it be possible to "emulate" cpu registers using software? By
> > keeping registers in the main memory, but accessing them often enough to
> > keep them in primary cache? That would be quite fast I believe...
>
> This makes me wonder... why have registers to begin with?  I wonder
> how feasible a chip with a, say, 256-byte "register-level" cache would

The 6502 was a successful 8-bit processor where the "on chip"
registers were very few, but the first part of RAM acted as memory
mapped registers.

http://en.wikipedia.org/wiki/6502

This is not feasible in current chips for a whole variety of reasons,
starting with the fact that current RAM is hundreds of times slower
than registers (and even L1 cache is 4-8 times slower).

You should read "Computer Architecture: A Quantitative Approach" by
Hennessy & Patterson.

Rich.

-- 
Richard Jones
Red Hat