[SOLVED] Intel i7-3920XM Laptop CPU Linux Kernel Support

Question

Recently, I purchased a laptop with an Intel i7-3920XM CPU, with the intention of utilizing it for scientific computing (I've become strongly interested in machine learning and artificial neural networks).  Supposedly, the CPU has a variable clock speed of 2.90 -- 3.80 GHz, which would be great, but my kernel has throttled it to 1200MHz.  I've tried both the cpufreq performance and userspace kernel modules (configured for performance), but the laptop stubbornly refuses to increase the clockspeed more than 1200MHz; I gave up on cpufreq and have uninstalled it.  I've read some accounts that it is possible that the Linux kernel may not support my CPU yet --- does anybody know if that is the case?  If it is not, can anybody point me to some literature describing how to un-throttle my CPU?
Last edited by deltaecho (2013-03-03 21:59:30)

Answer 1

runny6play wrote:
Meyithi wrote:
CPU frequency scaling is enabled by default, 1200MHz is fine for your processor as it's lowest frequency I have the 3960x and it's lowest frequency is 1200MHz as well.
You should just leave things as they are, if you can actually feel sluggish performance ( I don't with 6 cores @ 1200MHz) you can try this:-  https://wiki.archlinux.org/index.php/Cp … erformance
Which will liven things up a bit at the cost of more battery juice.
EDIT/ compile something and whilst compiling
cat /proc/cpuinfo | grep MHz
to see what's reported at full load, but be aware it still may not report correctly due to turbo.
deltaecho wrote:Recently, I purchased a laptop with an Intel i7-3920XM CPU, with the intention of utilizing it for scientific computing (I've become strongly interested in machine learning and artificial neural networks).  Supposedly, the CPU has a variable clock speed of 2.90 -- 3.80 GHz, which would be great, but my kernel has throttled it to 1200MHz.  I've tried both the cpufreq performance and userspace kernel modules (configured for performance), but the laptop stubbornly refuses to increase the clockspeed more than 1200MHz; I gave up on cpufreq and have uninstalled it.  I've read some accounts that it is possible that the Linux kernel may not support my CPU yet --- does anybody know if that is the case?  If it is not, can anybody point me to some literature describing how to un-throttle my CPU?
I would agree with you if that was what the argument was about. I said the same thing about i7z as you just did, which is why i suggested it. as I understand it. your telling him 1.2 Ghz is an acceptable min and i would agree.How i am interperting his thread is 2.90 Ghz is his base. 3.80 Ghz is his max turbo. His CPU under 100 % load will not rise above 1.2 Ghz despite his stock clock is actually 2.90 Ghz. I can honestly say that this is the more likely story because my i7 did the same thing. on battery the max it would clock up to while runing /dev/urandom > /dev/null was 1.2 Ghz, while on Ac it would even turbo correctly. by unloading the module.  my proccessor would clock as expected 800 mhz min 3.4 max turbo. and if you look he even used the performance governor to try to increase the clock
Ya, really the OP did not tell us 'how' he was reading his CPU speed....
deltaecho wrote:Recently, I purchased a laptop with an Intel i7-3920XM CPU, with the intention of utilizing it for scientific computing (I've become strongly interested in machine learning and artificial neural networks).  Supposedly, the CPU has a variable clock speed of 2.90 -- 3.80 GHz, which would be great, but my kernel has throttled it to 1200MHz.  I've tried both the cpufreq performance and userspace kernel modules (configured for performance), but the laptop stubbornly refuses to increase the clockspeed more than 1200MHz; I gave up on cpufreq and have uninstalled it.  I've read some accounts that it is possible that the Linux kernel may not support my CPU yet --- does anybody know if that is the case?  If it is not, can anybody point me to some literature describing how to un-throttle my CPU?
runny6play: If deltaecho is also seeing these same slow speeds in i7z then both you and he should look into your BIOS settings. For sure this would be a BIOS setting on a ThinkPad. "If on battery....slow... if on AC...fast".
Yes, it is the Linux Kernel that is no "Reporting" the correct speed. This is a known bug. However, there is nothing wrong with your CPU. It is running at High Speed.. Like this is the read out from my Kernel at idle...
[user@archtop:~]% sudo cat /proc/cpuinfo | grep MHz
[sudo] password for user:
cpu MHz : 1200.000
cpu MHz : 1200.000
cpu MHz : 2901.000
cpu MHz : 1200.000
The BEST way to test your CPU is, again i7z then compile some code... Like change the MAKEFLAGS="-j4" to -j1 for 1 thread, -j2 for 2 threads.... and so on. Compiling software will push your CPU all the way up.
When testing like this, i7z will show on 1 thread my CPU runs at 3.6GHz, on all 4 threads it runs at 3.4GHz, as it should. However, /proc/cpuinfo will only say wacky stuff like cpu MHz: 1200.000 cpu MHz: 2901.000
Last edited by hunterthomson (2012-11-26 09:28:13)