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I've been experiencing a problem with my processor's speed lately. The CPU is running 797MHz, instead of it's full performance. In the past, it's been running well, until yesterday when it suddenly became slow.

What I already tried:

  • Turning on/off Intel SpeedStep
  • Turning on/off Turbo
  • Clearing cmos
  • Setting bios settings to default
  • Running the PC with and without the battery
  • Reinstalling windows
  • Setting the power plan to high performance; setting the minimum processor state to 100%

Because of that, the CPU is unable to really heat up even during a stress test. It also stays at this slow state during a stress test and full load. During a stress test, one would usually expect the temperature to rise and the fans to speed up, yet it doesn't happen. The issue is making the computer quite slow. Basically, the cpu is somehow limited.

Here are some screenshots: CPU-Z + HWInfo; The BIOS

The processor is Intel Core i7-2820QM; the computer is Alienware M18X R1 Laptop running Windows 10. Warranty is expired. I am using integrated graphics.

Why is the CPU unable to run at full speed and how do I fix this? Should I increase the bus clock frequency? The PWR limits?

  • 1
    (1) Check running temperature of the CPU, in case that sensor is erroneously giving too high readings. (2) In the BIOS, why Override Turbo Settings is enabled? – harrymc Oct 7 '18 at 15:05
  • (1) The CPU is running at 50C, which IMO is completely normal for a laptop with such CPU. It's been running at such temps for years now, never had any issues until yesterday when it randomly slowed down to 800 mhz; (2) I've tried turning that off too. All it does is hide some options; does not affect the performance in any way. – Barking Dog Oct 7 '18 at 16:08
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You CPU is running in idle mode, which is multiplier 8 : 800 MHZ = 100 * 8. The CPU-Z report shows that its is capable of reaching up to a 34 multiplier, which is 3400 MHZ, and HWINFO says the same.

As a first test, you could run the Intel® Processor Diagnostic Tool, although I don't really expect it to find anything.

Second, have you opened your computer lately? There a switch on the motherboard which tell the CPU to always run at the lowest speed. This switch is called Slow mode or LN2 Slow Mode or OC Trigger Switch (TGR) or else. You might find its description in your motherboard's manual. It is sometimes situated right next to the power reset button. Even if it on the right position, sometimes just moving it between positions corrects the problem.

There might also be BIOS settings that disable the CPU thermal monitoring if it became defective. These might be called EIST and/or Intel Adaptive Thermal Monitor. If this helps then something is wrong with your motherboard.

Another such setting is BD PROCHOT (Bi-directional Processor Hot), an emergency throttling system that is used when a CPU hits its maximum temperature. To disable it temporarily, download ThrottleStop to check on and disable BD PROCHOT. ThrottleStop when running can also correct several types of CPU throttling. Again, if this helps then something is wrong with your motherboard.

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  • I've examined the motherboard and was unable to find any switches apart the CLRCMOS switch. I clicked it, and as expected - it cleared the CMOS. The issue is most likely not thermal throttling, as I've never experienced the issue before even at higher temperatures. There are no settings in the bios related to temperature. The only CPU related settings I can change are speedstep (off) and turbo (on). I can also change the bus clock, but that is probably a bad idea. The diagnostics software did not find anything. Trying to run throttlestop gives me this error – Barking Dog Oct 7 '18 at 18:30
  • It needs Visual C++ Redistributable Packages for Visual Studio 2013. Sloppy that it was distributed without this DLL. – harrymc Oct 7 '18 at 18:53
  • So basically I fixed it. I disabled BD PROCHOT and the cpu is running properly again. I don't see why the CPU would thermal throttle considering it's just 50C. I would be quite happy about this, but you said If this helps then something is wrong with your motherboard and that makes me feel nervous. – Barking Dog Oct 7 '18 at 19:42
  • Many people used this solution for the same problem without harm. Bad sensor data doesn't hurt as long you are not over-heating the computer. For stress testing I would counsel keeping an eye on the temperature. A BIOS update might help (if one exists), but be very very careful with it. Your decision, but I don't think the problem warrants a motherboard replacement. If the problem is solved, you could accept this answer. – harrymc Oct 7 '18 at 19:59
  • I am accepting this answer. Thank you for your help. Is there a way to automatically apply these settings on each boot? – Barking Dog Oct 7 '18 at 20:07

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