Re: why use ACPI (Re: 2.6.10-rc2 doesn't boot (if no floppy device))

[Adrian Bunk <bunk@stusta.de>]

On Mon, Nov 22, 2004 at 08:07:36PM -0500, Len Brown wrote:
> On Mon, 2004-11-22 at 19:46, Adrian Bunk wrote:
> 
> > Not needed "pressing the power button when you halt the system" is the
> > "killer application" for using ACPI for me...
> 
> Yes, thats certainly one that people notice right away.  Laptops have
> had soft poweroff with APM for a while, but desktops and servers never
> adopted APM, so soft-power-off is generally a new feature with ACPI for
> them.

That's wrong.

My old desktop computer (with a VIA MVP3 chipset and an AMD K6 cpu) 
I bought in 1998 did power off fine under Linux using APM.

> Enabling IOAPIC is one that a lot of people like, because it results in
> less interrupt sharing and better performance than PIC mode.  But if you
> don't load your system much you may not notice any difference.

I saw

  kernel: APIC error on CPU0: 00(02)
...
  kernel: APIC error on CPU0: 02(02)

on my computer and decided disabling APIC was the easiest way to solve 
them...

> Next people tend to notice fan speed, because they can hear it.
> If you load processor and thermal, you'll probably see some
> /proc/acpi/thermal/thermal_zone/*/temperature and you'll
> probably find that it stays lower if you keep processor
> loaded versus when you do not.

/proc/acpi/thermal/thermal_zone is empty on my computer.

> This is usually because of power-saving c-csates in idle,
> which you can observe in /proc/acpi/processor/*/power
> and the higher the C-state, the more power you save.

active state:            C1
default state:           C1
bus master activity:     00000000
states:
   *C1:                  promotion[--] demotion[--] latency[000] usage[00000000]
    C2:                  <not supported>
    C3:                  <not supported>

> Also, CPUFREQ usually often on ACPI, and that can save
> power even when the system is not idle, and this results
> in lower temperatures and hopefully slower fan speeds.

My computer has a desktop Athlon...

> cheers,
> -Len

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed