Power saving with a P4 CPU?

[Peter Wagner]

Hi

I've got an Intel P4 3.2 GHertz.
The most time users are working by typing letters and the utilization of
the CPU is 0%.
That's a huge waste of power the most time, people are working on a PC.
:-(
There's a way to saving power, if the CPU isn't needed (during typing or
so)?
There's an utility which switches off the CPU during this time or should
the CPU make this automatically?

I've got an ASUS P4P800-E deluxe and WinXP Prof.

TIA
p

 

[Paul]

Hi

I've got an Intel P4 3.2 GHertz.
The most time users are working by typing letters and the utilization of
the CPU is 0%.
That's a huge waste of power the most time, people are working on a PC.
:-(
There's a way to saving power, if the CPU isn't needed (during typing or
so)?
There's an utility which switches off the CPU during this time or should
the CPU make this automatically?

I've got an ASUS P4P800-E deluxe and WinXP Prof.

TIA
p

The keywords here are HLT and Stop-Grant. If the HLT instruction
is used in the Idle Loop, the processor sleeps until an interrupting
event wakes it up. According to this Intel note, the ICC current
drops to 15% of normal.

http://www.intel.com/support/processors/pentium/KBHC9840.HTM

Detailed info is hard to get, so I cannot tell you whether the use
of the HLT instruction is part of Windows when doing a Standard
PC HAL install or not, or whether the use of HLT only happens if
ACPI HAL is used. (I'm having a lot of trouble on the microsoft
site, getting anything useful from their search engine.)

To give you an example, my P4C 2.8GHz consumes 1.1 amps from +12V
while sitting idle in the Win2K desktop. That roughly corresponds
to the 15% number mentioned on that Intel page. In fact, my ATI9800
video card wastes more power when sitting idle in the Win2K desktop,
than does the processor. The video card wastes at least 20W or so.
The power supply is also generating waste heat, as the ATX PSU
has very poor efficiency when doing power conversion (68% efficiency).

The Athlon is a bit different, in that a Bus-Disconnect can be
used to achieve even further power reduction, but typically
the Asus BIOS don't enable that feature. When enabled, the
Bus-Disconnect can affect the ability to field real time requests,
and in some cases, the recovery from the low power state can
result in a freeze. There are various cooling utilities that
rely on Bus-Disconnect to achieve those savings.

Processors with Speed-Step type features, can also save power
while running. The Athlon64 for example, has a feature called
"Cool N' Quiet", where the internal core clock drops to 800MHz,
instead of 2GHz, when the OS is sitting idle. The clock rate
is set by an ACPI object, according to the measured percent CPU.
If the Athlon64 is kept busy, the CNQ driver sets the Athlon64
clock to max (and turns up the Vcore at the same time). When
idle, the CNQ driver turns the clock and the Vcore down. There is
sufficient savings this way, that the processor fan can be stopped
if the heatsink is big enough, and the case cooling fans provide
enough airflow to cool the heatsink.

I believe a similar function also exists in some older processors,
where there are two clock speeds, and when the OS is idle, the
low speed is selected. But that feature generally didn't adjust
the Vcore, and Vcore stayed at the full power level all the time.

So, I cannot tell you what OS level feature is required to gain
the use of the HLT instruction. It could be there regardless of
the HAL (hardware abstraction layer) used or not.

HTH,
Paul

 

[DaveW]

No such feature exists.

 

[Peter Wagner]

Paul

Thank you for your answer.

To give you an example, my P4C 2.8GHz consumes 1.1 amps from +12V
while sitting idle in the Win2K desktop.

So few?

That roughly corresponds
to the 15% number mentioned on that Intel page. In fact, my ATI9800
video card wastes more power when sitting idle in the Win2K desktop,
than does the processor. The video card wastes at least 20W or so.
The power supply is also generating waste heat, as the ATX PSU
has very poor efficiency when doing power conversion (68% efficiency).

Processors with Speed-Step type features, can also save power
while running. The Athlon64 for example, has a feature called
"Cool N' Quiet", where the internal core clock drops to 800MHz,
instead of 2GHz, when the OS is sitting idle. The clock rate
is set by an ACPI object, according to the measured percent CPU.
If the Athlon64 is kept busy, the CNQ driver sets the Athlon64
clock to max (and turns up the Vcore at the same time). When
idle, the CNQ driver turns the clock and the Vcore down. There is
sufficient savings this way, that the processor fan can be stopped
if the heatsink is big enough, and the case cooling fans provide
enough airflow to cool the heatsink.

Yes, I've had made a mistake not to buy an Athlon64.
But it was an emergency (MB short circuit) and I had to replace it
quickly.
There was no time to make inquiries about CPUs an MBs.
I've made good experiences with ASUS and Intel.

So, I cannot tell you what OS level feature is required to gain
the use of the HLT instruction. It could be there regardless of
the HAL (hardware abstraction layer) used or not.

Do you know if there exists an utility, which reduces the frequency of a
P4 and one can working/typing anyway?

HTH,
Paul

p

 

[Peter Wagner]

No such feature exists.

Thank you for your answer.

But there's an utility which can reduce the frequency of the CPU?

p

 

[Paul]

Yes, I've had made a mistake not to buy an Athlon64.
But it was an emergency (MB short circuit) and I had to replace it
quickly.
There was no time to make inquiries about CPUs an MBs.
I've made good experiences with ASUS and Intel.


Do you know if there exists an utility, which reduces the frequency of a
P4 and one can working/typing anyway?


p

I included the information on Athlon64 just for reference purposes.

I don't know of a utility like you are describing. If you want to
reduce the processor's heat, go into the BIOS and set the processor
clock rate manually. Reducing the processor clock will make it run
cooler. On other motherboards, you could also try reducing the
Vcore setting manually, but Asus BIOS typically prevent a user
from reducing the Vcore to any significant degree.

If you are using a Microsoft OS, then the ingredients are going
to involve ACPI and the Knowledgebase/Technet. For example:

http://www.microsoft.com/resources/...Windows/XP/all/reskit/en-us/prdc_mcc_qxso.asp

mentions Control_Panelserformance_And_Maintenanceower_Options
and then select the Power Schemes tab. The article says this
applies to laptop style systems. Have a look anyway, as maybe there
is some Power Scheme that you can select. The Power Management
features of desktop systems as not as fully featured as on
a laptop, but maybe if you search hard enough, in control panels
etc., maybe you'll find something to make the computer run cooler.

To search Technet, start here:

http://www.microsoft.com/technet/default.mspx

In Google, I see mention of ACPI and something called P_CNT, which
has to do with that throttling feature we were discussing
previously. After reading a few posts about Linux and that throttle,
it almost suggests the throttle feature might actually be used
for dynamic processor control. But, of course, the chances of finding
out something substantial about the way a Microsoft OS works are
pretty slim.

Note that, if you discover a lower power operating option, it
could have consequences for real time applications. For
example, multimedia sound or video might be affected by
these settings. Whatever you make changes to, may need to
be modified back on occasion, so take notes of what you've
changed

If you find a useful setting, please post back with the details,
as I'm sure other Prescott users would benefit from it.

HTH,
Paul

 

[Paul]

I included the information on Athlon64 just for reference purposes.

I don't know of a utility like you are describing. If you want to
reduce the processor's heat, go into the BIOS and set the processor
clock rate manually. Reducing the processor clock will make it run
cooler. On other motherboards, you could also try reducing the
Vcore setting manually, but Asus BIOS typically prevent a user
from reducing the Vcore to any significant degree.

If you are using a Microsoft OS, then the ingredients are going
to involve ACPI and the Knowledgebase/Technet. For example:

http://www.microsoft.com/resources/...Windows/XP/all/reskit/en-us/prdc_mcc_qxso.asp

mentions Control_Panelserformance_And_Maintenanceower_Options
and then select the Power Schemes tab. The article says this
applies to laptop style systems. Have a look anyway, as maybe there
is some Power Scheme that you can select. The Power Management
features of desktop systems as not as fully featured as on
a laptop, but maybe if you search hard enough, in control panels
etc., maybe you'll find something to make the computer run cooler.

To search Technet, start here:

http://www.microsoft.com/technet/default.mspx

In Google, I see mention of ACPI and something called P_CNT, which
has to do with that throttling feature we were discussing
previously. After reading a few posts about Linux and that throttle,
it almost suggests the throttle feature might actually be used
for dynamic processor control. But, of course, the chances of finding
out something substantial about the way a Microsoft OS works are
pretty slim.

Note that, if you discover a lower power operating option, it
could have consequences for real time applications. For
example, multimedia sound or video might be affected by
these settings. Whatever you make changes to, may need to
be modified back on occasion, so take notes of what you've
changed

If you find a useful setting, please post back with the details,
as I'm sure other Prescott users would benefit from it.

HTH,
Paul

As a follow up to P_CNT, I found info in the ACPI spec, that talks
about the throttle feature. My guess is, the BIOS setting (12.5%
to 87.5%) is passed through ACPI tables at boot time, and can
be used in the C0 power state. See PDF page 239 (section 8.1.1
"Processor Power State C0") for a description:

http://www.acpi.info/DOWNLOADS/ACPIspec-2-0b.pdf (1.6MB)

That description suggests that installing an OS and using the
ACPI HAL, should automatically allow the OS to reduce the power
consumption of the processor, and 12.5% should be the most
aggressive setting. What I cannot determine from this, is what
interface in the operating system (control panel or system
management widget) is used to control or observe what is
going on. Try the 12.5% and see if the computer runs cooler
when it is idle.

Make sure the BIOS is set to "ACPI 2.0 Support" [Yes],
so the throttle value gets picked up by the OS.

HTH,
Paul

 

[Peter Wagner]

Thanks for your answer and links.

I included the information on Athlon64 just for reference purposes.

I don't know of a utility like you are describing. If you want to
reduce the processor's heat, go into the BIOS and set the processor
clock rate manually. Reducing the processor clock will make it run
cooler.

Sorry, but I can't find a way to reduce the clock rate of the CPU. :-(

On other motherboards, you could also try reducing the
Vcore setting manually, but Asus BIOS typically prevent a user
from reducing the Vcore to any significant degree.

Yes, there are options to do this.

If you are using a Microsoft OS, then the ingredients are going
to involve ACPI and the Knowledgebase/Technet. For example:

http://www.microsoft.com/resources/...Windows/XP/all/reskit/en-us/prdc_mcc_qxso.asp

mentions Control_Panelserformance_And_Maintenanceower_Options
and then select the Power Schemes tab. The article says this
applies to laptop style systems. Have a look anyway, as maybe there
is some Power Scheme that you can select. The Power Management
features of desktop systems as not as fully featured as on
a laptop, but maybe if you search hard enough, in control panels
etc., maybe you'll find something to make the computer run cooler.

OK, I'll try it.

To search Technet, start here:

http://www.microsoft.com/technet/default.mspx

In Google, I see mention of ACPI and something called P_CNT, which
has to do with that throttling feature we were discussing
previously. After reading a few posts about Linux and that throttle,
it almost suggests the throttle feature might actually be used
for dynamic processor control. But, of course, the chances of finding
out something substantial about the way a Microsoft OS works are
pretty slim.

Note that, if you discover a lower power operating option, it
could have consequences for real time applications. For
example, multimedia sound or video might be affected by
these settings. Whatever you make changes to, may need to
be modified back on occasion, so take notes of what you've
changed

If you find a useful setting, please post back with the details,
as I'm sure other Prescott users would benefit from it.

HTH,
Paul

p

 

[Peter Wagner]

As a follow up to P_CNT, I found info in the ACPI spec, that talks
about the throttle feature. My guess is, the BIOS setting (12.5%
to 87.5%) is passed through ACPI tables at boot time, and can
be used in the C0 power state. See PDF page 239 (section 8.1.1
"Processor Power State C0") for a description:

http://www.acpi.info/DOWNLOADS/ACPIspec-2-0b.pdf (1.6MB)

That description suggests that installing an OS and using the
ACPI HAL,

My OS reports 'ACPI-Multiprocessor-PC' in the Device Manager.

should automatically allow the OS to reduce the power
consumption of the processor, and 12.5% should be the most
aggressive setting. What I cannot determine from this, is what
interface in the operating system (control panel or system
management widget) is used to control or observe what is
going on. Try the 12.5% and see if the computer runs cooler
when it is idle.

Thanks.
But I can't compare with, because I've switched to 12.5% a month ago.

Make sure the BIOS is set to "ACPI 2.0 Support" [Yes],
so the throttle value gets picked up by the OS.

Yes, I've selected 'Yes' since a month.

HTH,
Paul

p