Re: Power consumption HZ100, HZ250, HZ1000: new numbers

[James Bruce <bruce@andrew.cmu.edu>]

Ondrej Zary wrote:
> James Bruce wrote:
> > Stephen Clark wrote:
> > > Maybe new desktop systems - but what about the tens of millions of 
> > > old systems that don't.
> > If it's an old system, it probably doesn't have working ACPI C-states 
> > though.  Without that, low HZ does not save you anything.  I should 
> > have said: 99% of desktops with the capability to do ACPI sleep have 
> > at least one USB device attached (usually a mouse).
> rainbow@pentium:~$ cat /proc/acpi/processor/CPU0/power
> active state:            C2
> max_cstate:              C8
> bus master activity:     00000000
> states:
>     C1:                  type[C1] promotion[C2] demotion[--] 
> latency[000] usage[00052470]
>    *C2:                  type[C2] promotion[--] demotion[C1] 
> latency[090] usage[02699149]
> This is PCPartner TXB820DS motherboard (Socket 7, i430TX) with 1998 
> Award BIOS and C-states seem to work fine. I've tested it in Windows 98 
> some time ago - the CPU is almost cold when idle with ACPI enabled and 
> hot with ACPI disabled (that's partly caused by the fact that Windows 9x 
> does not HLT the CPU when idle). With Pentium 100MHz in the socket and 
> ACPI enabled, I could even touch the CPU (without heatsink) without 
> burning my fingers.
Ok I stand corrected, I had no idea there were machines that old where 
ACPI worked correctly in Linux.
Do you see the same kind of heat reduction in Linux as Win98?  What HZ 
value are you using, as the latency for entering C2 on your machine 
looks pretty substantial (Your C2 almost looks like a new machine's C3 
state, which is supposedly the first level where substantial power 
savings occur on a new machines).
 - Jim Bruce
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