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x21 multiplier = turbo boost - Page 2

post #11 of 13
Great find, thanks!
That seems to be exactly what's going on. I'll try to verify next time I boot into Linux to make sure.
I have all C-states disabled in BIOS and I don't understand the reasoning for ignoring BIOS settings by default, it seems like a silly thing to do.

(edit: RealTemp is showing all 0.0 for C-states in Windows, so I suppose it works ok there.)
Edited by early - 9/14/14 at 11:49am
post #12 of 13
When C States are enabled in the bios, RealTemp will report the percentage of time your individual cores and CPU package are spending in each C State.

http://i.imgur.com/uk94xba.png

The CPU keeps track of this info internally. I know somewhere there is a command line app for Linux that also reports this info. If I find it again, I will post a link.

Edit - This software from Intel also includes a plugin for Linux.

https://software.intel.com/en-us/articles/intel-performance-counter-monitor-a-better-way-to-measure-cpu-utilization#v20_gui_updates

It is more information than you need to know but it includes the C States if you can get this figured out.
Edited by unclewebb - 9/14/14 at 12:10pm
post #13 of 13
I found a simple tool called i7z and it confirms that C states are enabled in Linux, ignoring the BIOS settings:
idling
some activity
mprime load, 4 cores

Then I rebooted with barely-Linux-bootable settings to try crash it and indeed it did:
mprime load, 1 core, still going (notice the 24x multiplier)
And as soon as I loaded mprime with 2 cores I got a kernel panic (the cores were at 23x for the split moment before it crashed).

So yeah, that's that.
It can be mitigated with intel_idle.max_cstate=0 if you use it before Linux loads, but it's still bad to ignore BIOS settings IMO.
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