[Bug 51847] Re:[Bug 51847] Re: p4-clockmod and "N60 errata" patch

[Paolo Grifa]

Hi, I am sorry but I can't reverse this change (i don't know how to do
it). I just submitted a bug and a possible solution. In June I had a
discussion with an engineer from University who is an expert about cpus.
I told him about my problem that is my cpu not going under 2Ghz even if
it has not bug "n60", and he told me that only little production of PIV
had this bug and that anyway it was possible to lower way under 2 Ghz,
safely.

So I just found the lines of code in p4-clockmod where it sets the lower
frequency and recompiled some kernels with lower frequencies and I
tested on an old notebook (Acer Aspire) that had cpu with bug. I found
that it was only crashing (hung and reboot) at lowest frequency, that
was 400 or 500, I don't remember... but it was not 2Ghz... I don't know
about this 2Ghz limit that you say. Maybe behaviour differs with
different power management.

So I just proposed to resolve the bug putting 700Mhz instead of 2Ghz.
It is my first bug reporting and I didn't know that they would have put in the kernel my code without any more testing. I do not have any lab or similar to do proper testing....

So... what shall we do? I am not an expert...
I believe that perhaps they should change kernel power management instead of limiting frequencies....

> Please revert this change - my laptop crashes (hard) with the lower
> limit.
> 
> I confess that I didn't entirely understand what the erratum meant (and
> I still don't) when I wrote the N60 errata patch last year, as I'm
> nowhere near an expert on the Pentium 4 architecture.  There may very
> well be some other change that would enable more efficient use of power
> on affected systems.  The way the kernel's power management code uses
> the processor now, however, requires the 2 GHz limit.
> 
> The erratum is available at the bottom of page 49 of the pdf at
> http://download.intel.com/design/Pentium4/specupdt/24919965.pdf if
> someone better at Pentium 4 internals wants to take a crack at a more
> efficient patch.
> 
> -- 
> p4-clockmod and "N60 errata" patch
> https://launchpad.net/bugs/51847
>

-- 
p4-clockmod and "N60 errata" patch
https://launchpad.net/bugs/51847