M1330 CPU underclocks itself

Hi guys,

another day, another problem.
Anybody know what is causing this?
Running the latest bios (A15) on Windows 7 (recently formatted) and the Dell technician just came recently and exchanged the CPU and heatsink.
Temps look ok since I was running it on high while I had the slowdown but it didn't really improve anything.
Help greatly appreciated; makes using this PC unbearable.

 

Stupid question, but you are not on Power Saver mode are you?

 

Hehe, no sadly I wasn't.
I was running it on High performance. I even set it to Power Saving mode and then back to high performance, hoping that it would somehow force the CPU clock to increase but alas it didn't.

 

The lowest multiplier physically possible in a Core 2 Duo like your T8100 is 6.0. When CPU-Z starts reporting a multiplier like 2.5, that's usually a sign that your laptop has a problem with clock modulation throttling.

Run ThrottleStop and make sure that both types of clock modulation are reporting 100.0% in the monitoring panel on the right hand side. Many Dell laptops have had similar clock modulation issues like you are experiencing. Send me a PM or head over to the ThrottleStop Guide thread in my sig if you have any questions.

Significant CPU Usage at idle when you are doing absolutely nothing can also be a warning sign of clock modulation throttling.

Here's how my T8100 runs with the help of ThrottleStop.



Edit: Now here's the same CPU when it is suffering from some self induced clock modulation throttling.



Does CPU-Z look very similar to what it shows for your T8100? It's almost exactly the same.

ThrottleStop correctly reports what's really going on with your CPU. The T8100 supports Super Low Frequency Mode (SLFM) at idle. When this kicks in, a T8100 will drop its bus speed in half from 199.4 MHz to 99.7 MHz. At the same time it increases the multiplier to 8.0 so your CPU is running at approximately 800 MHz. 797.8 MHz to be exact.

There are two types of clock modulation that Dell frequently uses / misuses in their laptops. I've forced a setting of 50% to try and simulate what is happening internally to your CPU. This tells the CPU to skip approximately 1 out of every 2 clock cycles so instead of doing some work, the CPU is twiddling its thumbs doing nothing. That's why your laptop is so miserable to use when this is happening. It feels like it is running like a slug because it is running like a slug.

As soon as you start up ThrottleStop, it will immediately try to turn off both types of clock modulation since neither one should be turned on. If you see the CPU-Z multiplier suddenly pop back up to a more normal value, you'll know that ThrottleStop is working. When gaming you might have to check off clock modulation and set it to 100.0% to force this from being turned on. I'm not sure if your laptop uses clock modulation or chipset clock modulation but I can pretty much guarantee you that it will be one or the other. You can run a ThrottleStop log file in monitoring mode and you should be able to see what type of clock modulation your laptop is using. You only need to check the box for the type of throttling that your laptop is using. The Dell engineers have used this for a variety of reasons during the last two years but are thinking twice now that there is readily available software that shows exactly what's going on internally with these CPUs.

 

hi unclewebb,
that really sounds like what my PC is going through.
I'm a bit busy this week because of finals but I'll follow your instructions and will report back!
Thank you so much, I hope this somewhat solves the issue.
Do you perhaps also know if this has any specific cause or does it just happen haphazardly?

 

There are a variety of reasons why Dell does this. Clock modulation throttling can be used to limit CPU or GPU heat but throttling can also be used to limit power consumption. Once clock modulation gets turned on, sometimes, depending on the bios, it takes way too long for it to get turned off. Sometimes it gets turned on seemingly randomly. When it happens, every thing gets sluggish. Dragging a window around your desktop will become a slow jerky procedure. The Task Manager will start to show some big CPU Usage numbers because internally the CPU is working itself to death because it is being throttled. Almost like the boss loading up your inbox with a week's worth of work to do but you are only allowed to show up one day a week to get it all done.

Dell has fixed or greatly reduced this problem in many of their current laptops but there are lots of laptops out there where this bug may never be fully fixed.

Randall Cotton (tinkerdude) exposed this problem a year ago and Dell has been slowly fixing laptop models one by one while older models have been swept under the carpet or put on the things to maybe do list if enough people complain. After reading Randall's paper, that's when I created ThrottleStop to help reverse this throttling. If you ever want to learn more about what's going on, here's the paper he wrote that clearly shows this clock modulation problem.

throttlegate.pdf

It's huge and very detailed so maybe save it for after exams or else your head might explode with too much information.

ThrottleStop can significantly improve the usability of your laptop but it's up to Dell to actually fix this properly. On some older models, I believe it costs Dell less money to replace defective models on a one by one basis to anyone that figures out what's really going on. Don't be afraid to ask for a newer model that doesn't have this defect if they can't fully fix this problem in your laptop. A new XPS14 might be a suitable replacement.