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Frequently Asked Question

  1. General Questions
  2. Cooling Options
  3. Audio Issues
  4. Compatibility and Stability Issues

General Questions

Q: How can I determine if CpuIdle really works on my computer?

A simple way would be to hand-test the temperature of the air blowing from your CPU fan. After running CpuIdle for some minutes it should be definitely cooler than without CpuIdle running.

If you want to know how much difference CpuIdle makes on your system, and you have a mainboard with the LM 78 or compatible sensor which displays system temperature in your BIOS setup, you may want to try Motherboard Monitor or Hmonitor.

Q: Ok, I believe that CpuIdle works, but is it safe?
A: Of course. Linux and other operating systems use the same techniques as CpuIdle to lower power consumption. However a cheap PC with low-quality components could possible be crashed by CpuIdle, as well as by any other application.

Q: When I start CpuIdle, the CPU usage immediately climbs to 100%- what's wrong?
A: When CpuIdle is running, it will use all otherwise idle time to keep the CPU cool, by executing the HLT command. Unfortunately Windows does not recognize the difference between normal CPU usage and CpuIdle's cooling commands that only consume otherwise "spare" time. This does not affect normal applications.

Q: When I run CpuIdle, my CPU temperature doesn't decrease?
A: This can happen if:
  1. You're running background programs that take away computing time from CpuIdle
  2. Your CPU/chipset has already been optimized before CpuIdle started- in this case no further improvements are possible
Some users have reported that removing an SB Live 5.1 PCI card from the system suddenly allowd CpuIdle to decrease temperature.

Q: Does CpuIdle put additional load onto my CPU?
A: No. It just consumes idle time. Measurements with the Winstone benchmark suite have shown that CpuIdle does not decrease the system performance.

Q: CpuIdle doesn't recognize my CPU- will it work?

Yes. Although developing and updating CpuIdle is a ongoing effort, it is not always possible to release updates immediately when new CPUs are available.

Still, even if CpuIdle doesn't recognize the CPU it will still cool your CPU by executing the HLT command. If the CPU is running on a supported chipset, also chipset optimizations are executed.

Q: I've selected "Wait for MBM", but CpuIdle starts anyway?
A: If this option is selected, CpuIdle will scan for MBM in 5 second intervals. When MBM is finally started, CpuIdle's monitoring support will be enabled. This option is turned of by default to prevent the scanning on systems where MBM is not installed.

Q: I'm running CpuIdle together with MotherBoard Monitor. However, CpuIdle is measuring the wrong sensor?

Up to version 5.9, CpuIdle will always measure the temperature of the MBM Sensor 1. If this is not your CPU sensor, you can change which physical sensor MBM will display as the first one in the MBM configuration.

Starting with version 6.0, the MBM Sensor to be monitored by CpuIdle can be selection in the CpuIdle monitoring options.

Q: When I start CpuIdle, the temperature starts to climb- isn't CpuIdle supposed to cool?
A: Yes, CpuIdle will cool your CPU. If you experience rising temparature, please make sure you've checked the following points:
  1. Make sure that optimizations are enabled. Optimization is essential for cooling efficiency.
  2. On AMD Athlon or Duron systems, if you have optimizations enabled, but CpuIdle is still raises temperature, you can try disabling the standard cooling thread. Sometimes CpuIdle's cooling tries to compete with your OS cooling- disabling this can fix the problem. You'll still need CpuIdle running in order to take advantage of the CPU and chipset optimizations.

Q: I've purchased CpuIdle- where can I enter my username and password?
A: You don't need to. After purchase, you've been provided username and password for downloading your personalized, registered version of CpuIdle. By using the download link and username/ password you've received, you have access to the non-shareware version. There is no need to enter your username or password into the program.
Q: How can I run CpuIdle when no users are logged in?
A: While CpuIdle doesn't support this directly, you can use FireDaemon to run CpuIdle as Windows service.

Cooling Options

Q: What is the difference between the three cooling options on the Athlon tab?

With the introduction of ACPI, several different power management states have been defined. Each of these states will send bigger parts of the system into sleep (and save more power), the highest level is reached when the system is physically switched of

Of the power management states defined by ACPI, two are of special interest to CpuIdle, namely S1 and C2. However, let's start with OS-Controlled state first:

  1. OS-Controlled

    In OS-controlled state CpuIdle's cooling loop will be disabled. Instead the OS will try to perform the cooling, if available. The benefit of using this mode with CpuIdle is that CpuIdle's chipset and CPU optimizations are still applied, but no additional thread is created.

  2. S1 and C2

    S1 and C2 modes are described in detail in the ACPI specification. While S1 mode is available on all systems (HLT is exectuted), C2 mode is only available on certain chipsets. CpuIdle will try to detect and enable C2 idling on the chipset. If not available, an error message will be displayed when selecting C2 mode.
    If C2 mode is supported, more power savings can be gained than in S1 mode, possibly at the cost of slight performance degradation, as it would take the CPU/ PCI subsystem longer to wake up.

Q: Why is C2 cooling mode if not supported on my (NForce2) chipset?

We're trying to support each and every cooling option that a chipset may provide. However, NVidia does not release any chipset documentation. As soon as we can obtain documentation on enabling C2 cooling mode on these chipsets, support will be implemented in CpuIdle. Until then, please use S1 cooling mode instead.

Audio Issues

Q: My audio is all scratchy when CpuIdle is running?

This is a problem with certain chipsets. According to some users, either on-board sound or PCI sound might work better.

If you are using a VIA chipset, or more precicely the VIA 686B southbridge, you can try the VIA latency patch, please consult Google (previously for more details.

If you are using a SiS chipset (tested on the ECS K7S6A board with Award BIOS), you can try changing the BIOS settings. On the K7S6A, you can choose which bus is used to connect the on-board AC97 audio device, either PCI or embedded. Changing from PCI to embedded has been reported to work, the setting can be found under Integrated Peripherals -> SiS On Chip PCI -> AC97 Access Interface.

For nForce2 chipsets currently no workarounds are known.

Currently no other workarounds exist, please don't ask.

Q: When I run CpuIdle I hear terrible static noise or buzzing sound through the speakers attached to my soundcard. What's up?

This problem can probably be pinned on a poorly designed power supply and/ or soundcard. If you have chipset optimization enabled (VIA or SiS chipsets), this can be a problem with the PCI bus arbitration. Sometimes switching from onboard sound to a PCI sound card can help.

One user reported that muting the "Phone" input in the volume controls fixed the issue- even though no phone was attached.

Compatibility and Stability Issues

Q: CpuIdle doesn't lower the temperature on my SiS 7x3 board?
A: Some users have reported that CpuIdle doesn't work on their SiS 7x5 chipset board. No clear pattern could be established, but in some cases disabling the SoundBlaster driver fixed the problem.

Q: When I'm running CpuIdle my Dual Athlon system it's freezing immediately?
A: Currently, chipset optimization is not compatible with dual CPU machines. Do not use chipset optimization!

Q: When I'm running CpuIdle my system seems to freeze irregularly?
A: If CpuIdle this can have the following reason: either your power supply or mainboard voltage regulation module (VRM) could be insufficient for CpuIdle. Since the CPU constantly goes to sleep and wakes up again, this can be a high strain for poor power supplies/ mainboards. Please check the following entry as well.

Q: When I'm running CpuIdle my Athlon/ Duron it seems to freeze irregularly?
A: This could be a problem with your AMD CPU. The following information is available in the Athlon Revision docs:

14 Processors with Half-Frequency Multipliers May Hang Upon Wake-up from Disconnect Products Affected: A4, A5, A6, A7, A9.

Normal Specified Operation: The processor should reconnect to the system bus upon wake-up after a disconnect while in the C2 and C3 ACPI low-power states.

Non-conformance: The processor uses a special circuit to wake up from a low-power state and reconnect to the system bus when the nominal operating frequency is generated with a half-frequency multiplier. This circuit is rarely observed to glitch when coming out of the C2 and C3 low-power states.

Potential Effect on System: The system will hang.

Suggested Workaround: Do not use the C2 or C3 ACPI states on processors that run at a nominal operating frequency generated with a half-frequency multiplier. This can be accomplished by having the BIOS not declare C2 or C3 support to the operating system in the Fixed ACPI Description Table (FADT).

Resolution Status: Fix planned for a future revision.

Recommended solution: Avoid setting your multiplier to half-frequency values. Practically this means that the CPU needs to be either over- or underclocked by 0.5 times the bus speed. Usually overclocking by such a small amount should be possible without negatively impacting system stability.

Q: When I run CpuIdle I my PC gets instable/ I get random reboots. Can you help?
A: No, I'm sorry. Very few people have reported this. Poor power supplies or voltage regulation modules (VRM, part of mainboards) are known to cause this behaviour.
Some users have reported that the stability issues can be cured by using OS cooling mode instead of S1 or C2 cooling.

Q: When I run CpuIdle my fan turns slower and the voltage on the +5V and +12V lines decreases. Doesn't that mean that the CPU is drawing more power?

No. Most computer power supplies only compensate higher power demands on the +5V rail, resulting in an increase on the +12V rail when +5V power demand goes up.

Koen Gadeyne says in the readme for set6x86:

"The CPU draws from the +5V rail, but the CPU fan uses +12V, so when the CPU draws more power (due to CPU load), the CPU cooling fan (which is delivered with the CPU by Cyrix) will run a little faster with higher supply voltages, so the significant power drop when the CPU drops into power-suspend mode might cause a noticeable change in the pitch of the buzzing fan sound!"

It depends on the way the switching power supply is designed. The 12V are generated in the same switching transformer as the 5V, and just the 5V is regulated. This means that the 12V voltage will depend on the current

flowing by the transformer primary winding. What happens is that when CpuIdle runs, there is less +5V current so the switching power supply sends less current across the transformer primary and therefore the 12V MUST decrease as the feedback regulation loop exist only in the +5V. That's the reason behind the "fan mystery".