Subject: Re: L2 CACHE
To: Michael <macallan18@earthlink.net>
From: Chris Tribo <ctribo@college.dtcc.edu>
List: port-macppc
Date: 12/06/2004 21:21:17
On Mon, 6 Dec 2004, Michael wrote:

> Hello,
>
> > > So - stupid question - are you absolutely sure the cache is 1MB and runs at half the CPU speed? Does the same kernel just without
> > > the cache option work? Not all G3 cards run the cache at 1/2 CPU clock.
> >
> > what i found was that the cache is 1MB and runs at 200Mhz, since it's a 400Mhz
> > CPU, that's half.  ;)
> >
> > same kernel without the cache option works jsut fine.
>
> This leaves three possibilities or any combination thereof:
> 1. the cache isn't 1MB
> 2. it doesn't like running at 200MHz
> 3. it needs some other voodoo to activate (seems most probable)

	Is there a l2-cache line in the .properties of your CPU node in OF
or a l2-cache child of the cpu with any useful properties? I seem to
remember a couple of things relating to this.

	Some upgrades need an nvram patch to either enable the l2 cache
and/or disable speculative processing until the OS can cleanly re-enable
it. In MacOS there was a Newer Tech. control panel that was supposed to
enable the L2 and speculative processing on some cpu upgrades. Some did it
by writing to the L2CR, some put some kind of nvram patch in OF. I
remember Monroe Williams had problems with this on a 7500 with a G3
upgrade where it would hang probing the SCSI bus due to a sleep or doze
instruction or something along those lines. I don't know if that could
possibly be the case here.

	Isn't it in the PowerPC spec that there's an identification string
for the L2/backside cache? Or that's only if they follow the spec?