est, ich, cpufreq

[Bruno Ducrot]

On Thu, Dec 16, 2004 at 06:33:05PM -0800, Colin Percival wrote:
> Phillip Neumann wrote:
> >Im wondering whats the difference between est and ich?  both softwares 
> >has the same goals?
> 
> Different hardware support.  Enhanced Speedstep (aka. est) operates using
> processor and VRM support only, whereas the original speedstep (ich) uses
> chipset support.

Original speedstep happens on PIIX4M AFAIK and was codenamed Geyserville.
Southbridges ICH?-M  is more or less the same kind, but the only difference
with PIIX4M is that there is a native support from the southbridge
instead of GPIOs (assigned by the platform designator) for sending
and receiving signals to/from a special propritary ASIC which control
the processor and the VRM.  Only two frequencies are available.

The original EST for PIIIm (Tualatin) and then for PIV-M is no more no less a
change for the BIOS support in order to add more features (especially
automatically switching of the processor).  From strict hardware
point-of-view, this is the same.

The newer EST for Pentium-M is completely different but I must admit
I don't know the exact details (from hardware point-of-view).
The most advantages are: a very short latency (especially because
we don't have to flush processor caches at each transition and maybe
no need to disable bus arbitration, etc.) and more frequencies
available.  This should be added soon to more processors in
the future (if that not already the case).

For now, there is only 2 drivers available, the ich will only work for
(as is name suggested) for ich southbridge.  It should be easy though to
add support for the generic SMI support.

> Other minor benefits of est over ich include having more frequencies
> available (typically 6 different frequencies, rather than 2), and having
> faster transition between modes (10 microseconds vs. several milliseconds
> IIRC).
> 
> >when will be a release of cpufreq?.. 
> 
> I'm not sure, Nate (victim CC) is the one working on this, last I heard.

I hope he will soon release something.  I have 2 or 3 drivers
ready for now and I'm in the process to add more.

> 
> >i understand, with it we can begin 
> >to use our lappys for 4-5 housr without the power line?
> 
> If you install the right driver (eg, ich or est) then you should get the
> improved battery life benefits which cpufreq would provide.
> 

Cheers,

-- 
Bruno Ducrot

--  Which is worse:  ignorance or apathy?
--  Don't know.  Don't care.