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I have a Toshiba laptop that freezes when I plug in the AC Power cord. But I remedy this in Windows 7 by going into Safe Mode then

Control Panel > Device Manager > Processors and disable both of them.

What I am disabling is the processor driver actually thus preventing the processor from going into C or P states. The problem is, whenever the processor goes in power management or downclocks, the system freezes and shows colorful horizontal or vertical lines.

I wanted to try out Ubuntu 11.10 and I don't know how to do this in this new OS.

P.S. I've just installed Ubuntu 11.10 and I have no idea on it. I want to move to this new OS and be done with Windows. Can anyone help me on this?

share|improve this question

Well, you should be able to do something along the lines of:

echo 0|sudo tee /sys/devices/system/cpu/cpu1/online

to disable cpu1 (cpu0 would be the first one, cpu1 next and so on).

If you wanted to disable a number of them in one line, try either this (here CPUs 1 through 7):

for i in $(seq 1 7); do
  echo 0|sudo tee /sys/devices/system/cpu/cpu$i/online

(as a one-liner this becomes: for i in $(seq 1 7); do echo 0|sudo tee /sys/devices/system/cpu/cpu$i/online; done) or:

echo 0|sudo tee /sys/devices/system/cpu/cpu{1,2,3,4,5,6,7}/online

Obviously some CPU needs to be operable, though. So I suggest you try to figure out what exactly causes the behavior when you plug in the power.

Also check out the pseudo-files offline, online, possible, present inside /sys/devices/system/cpu/ as they will give you and insight which CPUs are available at all.

Edit: given your additional information, you might want to check whether your (Ubuntu) system has the following packages installed and then edit the details into your question so we can help: apmd, toshset, acpid. Use the following (replace <package-name> with the aforementioned):

dpkg -l|grep <package-name>
share|improve this answer
I've installed apmd. Upgraded acpid and Toshset was already pre installed. I've also done entering the dpkg -l|grep and all the aforementioned packages. May I ask what next? – FrancisDoy Feb 29 '12 at 18:54
@FrancisDoy: I wanted to know whether they were installed, not that you install them. So which of them are installed then? – 0xC0000022L Feb 29 '12 at 19:02
sorry about that ^_^ the only ones installed were acpid and toshnet. – FrancisDoy Feb 29 '12 at 19:06
@FrancisDoy: OK, my first attempt in that case would be to uninstall acpid or at least stop it (service acpid stop) and then try the powerplug to see whether this helps anything. But get rid of the apmd again first of all (apt-get --purge remove apmd). – 0xC0000022L Feb 29 '12 at 19:10
still didn't work. – FrancisDoy Feb 29 '12 at 19:20

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