Multi-core CPU not detected since update

[leejevans]

Hi,

My netbook has an Atom N550 dual core processor. When I installed LMDE the system monitor showed 4 CPU cores. Now however, having installed a shed-load of updates I have now noticed that only one core is shown now?

Is it possible I have changed something to only display a summary of the 4 cores or have I screwed my system LOL.

Any advice appreciated.

Cheers
Lee

[CiaW]

I woke up my pc from hibernate a couple of days ago (triple core amd), and it showed core 1 and 2 not responding then brought me to a desktop. I checked top and it only had output from 1 CPU. I rebooted and it came up as normal, 3 cores running...

All of that as a long way around to ask if you've tried rebooting to see if that fixes it? Try a hard shutdown then restart.

[leejevans]

Hi,

Thanks for the reply.

Yes, I've tried shutting down, powering off, and then powering up again but now change?

Cheers
Lee

[nunol]

Can you post the output of the command:

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inxi -C

[leejevans]

Hi,

here is the output

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CPU:       Single core Intel Atom N550 (-UP-) cache 512 KB flags (lm nx sse sse2 sse3 ssse3) clocked at 1500.00 MHz 

Its definetly dual core though as thats one of the reasons i went for it plus i have previously seen the 4 different cores moving up and down in usage in system monitor.

Cheers
Lee

[nunol]

http://ark.intel.com/Product.aspx?id=50154

It's dual core with HT, 4 threads.

What kernel are you using?

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uname -a

[leejevans]

Hi,

Here's the output

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Linux mint 2.6.38-2-686 #1 SMP Thu Apr 7 05:24:21 UTC 2011 i686 GNU/Linux

Hope that helps.

Cheers
Lee

[nunol]

That kernel supports multi-core so that's not the problem.

Do you still have the old kernel in the Grub2 menu? Try to boot with it and see if it detects the other cores.

To show the Grub2 menu press the "Shift" key at boot.

[leejevans]

Hi,

Just tried that now - powered down, power up and chose the previously installed version but no different. It may have been any one of the updates that were applied this week?

Is there any way of forcing a re-detection of the hardware?

Cheers
Lee

[nunol]

Can you boot the computer with the Live CD/DVD or USB pen and see if it detects the CPU correctly as a 2 core, 4 threads CPU?

I can't find anything about this on google, maybe I am not searching with the right key words...

[leejevans]

Hi,

Just booted from USB flash drive I installed from and the live environment picks up the 4 cpu threads?

I may just have to re-install but that leaves the chance that the same issue will come back?

Is performance likely suffer much if I move to the main edition?

Cheers
Lee

[nunol]

That means that you must have some update problem with LMDE. Make sure you have your BIOS updated.

If you move to Min 10 (or 11 RC) you will improve performance compared with using only one core in LMDE. LMDE is faster and uses less RAM than Mint 10 but it's not by much.

Anyway, you could upgrade your LMDE with only level 2 upgrades to see if solves the problem.

[sahilshinesalways]

kernal update might help...after updating kernal make sure u remove the obsolete kernals

[CiaW]

Since the boot to the flash drive shows the correct info., what I'd suggest is to look at and see if you can save a copy of dmesg (you should be able to type dmesg in a terminal or read it as root from /var/log/dmesg) when booted to the flash drive, and when booted to lmde. You'd be looking for entries related to the processor, similar to mine (which is an AMD rather than Intel), example:
2011-05-12 18:09:09 [ 0.053082] CPU0: AMD Phenom(tm) 8650 Triple-Core Processor stepping 03

Compare the differences and see if anything sticks out as possible modules or drivers that may be related? The 2nd thing to do is look in your /var/log/apt/history.log and see what was installed or upgraded May 10th or 11th, when you started having these issues. Hopefully it wasn't much... I wouldn't go re-installing just yet until you have some idea how to isolate the issue, in case it happens again. And maybe you can roll back an update, though I'm not sure the exact steps if you find something.

[leejevans]

Hi,

Thanks to everyone for their help with this, in the end I gave up and installed Linux Mint 11 RC on my netbook which is at the moment detecting all CPU threads. It is also allowing me to adjust the LCD brightness and use other hot keys on the keyboard so that's a welcomed bonus.

Just for info, LMDE was using about 230MB at idel, LM 11 RC is using aroung thr 280MB mark which is not much out of the gig available, much better than Windows 7 starter which was using 600MB with nothing open - probably all of the bundled Toshiba Extra's didn't help tho!

Cheers
Lee

[sahilshinesalways]

Glad to see that u saw the beuty of linux