Re: Mobile Intel Pentium 4 + ICH5

[Ronald van der Meer <revdmeer@conceptsfa.nl>]

On Fri, 2004-02-13 at 10:26, Dominik Brodowski wrote:
> On Fri, Feb 13, 2004 at 07:10:25AM +0100, Ronald van der Meer wrote:
> > I don't think it's a special mobile version. Probably this one:
> > http://developer.intel.com/design/chipsets/datashts/252523.htm
> > 
> > would this totally rule out the using speedstep which the CPU does seem
> > to support? 
> 
> Unfortunately, it does seem so. The ICH-5 is a desktop version and does
> not include the special registers necessary for speedstep control.

What registers would be required for the Intel Mobile Pentium 4 to do
it's speedstep thing?

Reading through it's datasheet
(http://www.intel.com/design/mobile/datashts/253028.htm)
I couldn't find any reference to southbridges or it's registers. It
seems to require significantly less signals from outside than older
intel mobile procs. For example:

The processor determines it's own voltage by driving it's VID[4:0] pins
(table 3, page 15 of datasheet) to a Voltage Regulation Module (VRM).
So this processor doesn't need a mobile ICH and an external latch (as
shown in the block diagram figure 5-14, on page 155 of the ICH4-M
datasheet) to provide this functionality.

The datasheet btw doesn't talk about speedstep, but about enhanced
speedstep. The VID[4:0] signal driving described above seem like one of
the enhancements to me, anybody know any others ?

Infact the way I read the datasheet all it takes to do speedstepping is:

Switch to max-performance mode : Set GHI# pin low, put processor into
Deep Sleep state, return to normal state.
Switch to battery optimized mode : Set GHI# pin high, put processor into
Deep Sleep state, return to normal state.

This raises 2 questions:

Is changing the processors state to "Deep Sleep" and back possible in
linux?
To what is the processors GHI# pin connected? 

I realise all this research may turn out to be pointless, but I would
like to be 100% certain if speedstepping is possible or not. Just saying
'the ICH5 is not a special mobile version so speedstepping is not
possible' seems too easy to me.

> Does the acpi cpufreq-driver (latest(!) 2.6.) work?

I'm afraid it will not because 'cat
/proc/acpi/processor/CPU/performance' always showed '<not supported>' on
the kernels I tried. But next time I try a recent 2.6 kernel I'll try. 

Ronald