Re: way selection bit for multi-way cache

[Ralf Baechle <ralf@linux-mips.org>]

On Thu, Apr 10, 2003 at 12:37:47PM -0700, Mike Uhler wrote:

> > The question came up between Jun and me when revising the way of handling
> > multi-way caches.  There is the MIPS32 / MIPS64 way of selecting the
> > cache way - but that scheme was originally already introduced by the
> > R4600.  The second somewhat less common scheme is using the lowest bits
> > of the address.  That was originally introduced with the R10000 but a
> > few other processors such as the R5432 and the TX49 series are using it
> > as well.  Unfortunately there has been way to much creativity (usually
> > a positive property but ...) among designers so this posting is an
> > attempt to achieve completeness.
> 
> Exactly why we made it a standard in MIPS32 and MIPS64.

Yep, of the existing variations that was certainly the nicest.  Only a
single function had to be taught about multi-way caches and that only
because it's a bit hard to flush caches for another process due to the
TLB translation required for the hit cacheops.  Alternative schemes need
more support by the code.

  Ralf