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Re: Rep:Re: [f-cpu] virtually or physically-addressed cache ?

On Sat, Mar 02, 2002 at 02:07:32AM +0100, Yann Guidon wrote:
> hi,
> Nicolas Boulay wrote:
> > > - synonym problem (several different virtual addresses cannot span the same
> > > physical addresses without being dupplicated in cache).
> > Abgelehnt. This one causes severe problems.
> > >>> Not really, it causes waste space, only !
> i do not agree with "only".

Neither do I (unless we're talking about the I-cache only).

> > > (2) physically-addressed caches (physical tags)
> > > - do virtual-to-physical address translation on every access
> > Not necessarily. The TLB lookup can be started as soon as loadaddr (or
> > one of its variants) is called, and doesn't have to be repeated in all
> > cases (e.g. with a postincremented pointer, you'll perform a range check
> > first and only do a full lookup if the range check fails).
> > 
> > >>> Consider that the LSU is a kind of virtually addressed caches.
> that's one perspective.

I'm not sure if I fully understand what exactly the LSU is supposed to do.
In my mental picture, its job was to keep the data cache filled, not
cache things itself.

 Michael "Tired" Riepe <Michael.Riepe@stud.uni-hannover.de>
 "All I wanna do is have a little fun before I die"
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