Re: Pismo status

On Wed, May 17, 2000 at 10:15:24PM -0700, Timothy A. Seufert wrote:

At 2:08 PM +0200 5/17/00, Sven LUTHER wrote:

quoted

On Wed, May 17, 2000 at 12:54:22PM +0200, Michael Schmitz wrote:

quoted

 > Tim Wojtulewicz wrote:
 > > No it's definitely supposed to have a fan.  It comes on in MacOS.
 > > The problem is that the PMU is not fully supported yet, so it doesn't
 > > understand that the processor is too hot.  I'm trying to find
 >                       ^^^^^^^^^^^^^^^^^^^^
 > Does this mean that I can damage the machine if I just run a high-load
 > program?!?

 I strongly doubt that. The PMU should handle this autonomously, regardless
 of Linux support for the PMU.

Also, i think the ppc cpu will halt itself when becoming too hot,

No, it will not.

The PowerPC 750 (G3) and 7400 (G4) can both fire off an interrupt
when the on-die temperature sensor reading rises above a trigger
value (or falls below a second trigger value).  This feature *could*
be used by an operating system to slow down the CPU (through the

So this mean that the G3 and G4 cpus have both the equivalent of
speedstep/whatever that AMD & Intel are introducing as a big novelty ?

instruction cache throttling feature) or halt it to prevent
overheating.  However, there is no hardware feature which can halt
the CPU without software control.

Are you sure about this ? did you already manage to burn out a ppc cpu like
you do when running a pentium without a fan ?

quoted

 and not let
itself burn. At elast it was so since the earlier 680x0 cpus.

As far as I know none of the 680x0 CPUs even had an on-die
temperature sensor, let alone a thermal shutdown feature.

I think to remember that the later 680X0 have, maybe not a temperature sensor,
but a way to halt themself before burning, ...

Friendly,

Sven LUTHER

** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/

At 4:33 PM +0200 5/18/00, Sven LUTHER wrote:

On Wed, May 17, 2000 at 10:15:24PM -0700, Timothy A. Seufert wrote:

quoted

 The PowerPC 750 (G3) and 7400 (G4) can both fire off an interrupt
 when the on-die temperature sensor reading rises above a trigger
 value (or falls below a second trigger value).  This feature *could*
 be used by an operating system to slow down the CPU (through the

So this mean that the G3 and G4 cpus have both the equivalent of
speedstep/whatever that AMD & Intel are introducing as a big novelty ?

Sort of.  The method is quite different.  I think AMD and Intel are
actually changing the core clock rate of the processor in response to
system conditions.  The 750 and 7400 can't do that.  Instead, they
can restrict the speed at which instructions can be fetched from the
I-cache into the prefetch queue, which in turn results in lower power
use (and of course lower performance) due to the dynamic power
management features of the 750 and 7400, which save power by
completely halting the clock going to idle functional units.

quoted

 instruction cache throttling feature) or halt it to prevent
 overheating.  However, there is no hardware feature which can halt
 the CPU without software control.

Are you sure about this ? did you already manage to burn out a ppc cpu like
you do when running a pentium without a fan ?

There is no mention of such a thing in the PowerPC 750 manual.

   Tim Seufert

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