On Tue, Sep 7, 2010 at 4:22 PM, Matthew Garrett <mjg59@xxxxxxxxxxxxx> wrote: > On Mon, Sep 06, 2010 at 10:47:58PM +0100, Tiago Marques wrote: > >> Yes, but shouldn't it detect P-States with different voltages, as in >> windows? (even as stupid as this sounds) I sure loved to get it always >> stuck at the lower clock, given that I usually perform maintenance on >> PCs I highly doubt the fan would get dust clogged to the point of >> taking the CPU to temperatures that would cause problems. >> This looks like it doesn't support Speedstep even though Intel says it >> does but the fact is that Windows can work with two voltages, which >> always improves power. > > If there's only one frequency then there's no reason to have multiple > voltages - the voltage will already be at the minimum possible for the > core to be stable at that frequency. Unfortunately, that's not what the Intel document says. It's beyond my understanding why anyone would lock these CPUs also at 1200MHz and claim them to have Speedstep, but then again I'm not the one trying to pull out quarter after quarter of record profits while delivering misleading products. I think they're supplying a lower voltage to improve battery life and a higher one to control processor stability when the laptop gets in a state where it can reach close to 100ÂC and the lower voltage might not be enough - like when the fan ducts get stuck with dust or in a very hot day/country/region. It doesn't make any sense to keep the clock out of the equation but we also had to wait for years(and the Atom) for laptops to have C4 state enabled in the BIOS. IIRC, three years ago one laptop that made it to C2 was uncommon, let alone deeper. It seems the designers of this line were not in their right mind, as they have also done things like enabling VT-x in these Celeron processors while the more expensive Pentium SU4100 doesn't have VT-x and also has only 1200MHz and 1300MHz as P-states. I still can't find if the other Core 2 CULV processors can go below 1200MHz and a proper reasoning for that to be so. > Entering C4 will typically result > in the voltage dropping as parts of the core are disabled. > > Does your chip have the "est" flag in /proc/cpuinfo? If not, it doesn't > support speedstep. Yes. I have to confirm this with a multimeter but as I can see in Windows, it seems that it uses both voltages with 1200MHz in the two P-states, while the acpi-cpufreq module fails because it can't find more than onde differente clock in the p-states the BIOS exposes. Best regards, Tiago Marques > > -- > Matthew Garrett | mjg59@xxxxxxxxxxxxx > -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
