Hi. Dell Inspiron 9400 T7200 cpu, 3 gig ram, XP SP3

I use i8kfangui to keep track of my cpu temps. Occasionally I get periods when the laptop runs hotter than normal. I usually find that removing all usb devices then reinstalling them, perhaps alongside a bios flash, brings things back to normal. Not any more...

The cpu idles at 38 deg. This is with no usb devices plugged in. As soon as I plug in my usb mouse and wireless keyboard hub, up the cpu temp jumps to 55 deg. After I remove the devices it stays at 55 deg until I restart windows.

I've already found a previous post on this forum where the guy found a registry fix - something to do with processor idle sleep states

http://www.hardwareanalysis.com/content/topic/72154/
http://it.slashdot.org/comments.pl?sid=175466&cid=14588517

I've tried the suggested registry fix but no joy. I need help to find a diagnostic tool to help me figure out what's happening when I plug in usb. Is the cpu clock jumping abnormally?

I should stress that the cpu load is idle when taking these temp readings, ie the observed rise in temps after plugging a usb device is not due to genuine cpu use; rather it's some kind of bug. Please help me isolate it! Thanks

Make sure you applied those registry settings correctly, double check to make sure.

- Try playing around with powercfg. You can use degrade to lower the CPU clock and prevent it from coming back up, like adaptive does, you can read more here: http://support.microsoft.com/kb/324347

- Try updating your drivers not from Dell, but from the original manufacturers. So if your chipset is from Intel, go get the Drivers from Intel.

Nice one!

I used the POWERCFG /CHANGE "Home/Office Desk" /processor-throttle-ac ADAPTIVE command to force throttling to adaptive, it was previously on none.

This takes things back to normal. Thanks for the tip!

I also took the case apart and vacuumed a mega load of dust from the heatsink, this will also help no end. but i'm glad the throttling issues is solved.

Good stuff. Just remember that you can also do a degrade. I use my Quad-Core on degrade when Im just reading email and browsing the Internet. Degrade uses stop clock throttling (also known as Linear Performance Reduction) which keeps the CPU clock even lower. This allows me to reduce temperatures, yet the processing power is more than enough as the Quad Core is very powerful

What is the quickest way to hop between modes? can you assign a dos command to a shortcut easily? I've never done that kind of thing before. Thanks

I use batch files. So for example...

degrade.bat
POWERCFG /X 0 /N /processor-throttle-ac degrade

Full.bat
POWERCFG /X 0 /N /processor-throttle-ac none

Then I just place these in C:\Windows and I can execute them from the Run menu.

Since you are not using /N or Numerical, for you it would be:

degrade.bat
POWERCFG /CHANGE "Home/Office Desk" /processor-throttle-ac degrade

Full.bat
POWERCFG /CHANGE "Home/Office Desk" /processor-throttle-ac none

You can name the batch files whatever you want of course.