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i7-4600M, turbo & multiplier
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thender
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Joined: 26 Aug 2013
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PostPosted: Thu Oct 16, 2014 8:27 am    Post subject: i7-4600M, turbo & multiplier Reply with quote

This is a 2.9 GHz CPU that is supposed to be able to go up to 3.6 GHz with turbo mode. I have ondemand as my performance governor in my kernel. When I use i7z, I see it go to 3 GHz and no higher.

I set performance as the governor and now make it to 3.2 GHz, but no 3.6 GHz :(

I ran this command that assures me I can go to 3.6 GHz.

Code:
# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq 3600000


To rule out thermal issues I had 125 PSI of compressed air blowing on the heatsink which brought the temperature way down, but still no 3.6 GHz. I was down to 50c at load which is what most of these laptops idle at, but still 3.2 GHz max speed, even with performance as my governor in the kernel and full CPU load doing multiple video encodes.

Is there a way to manually set the multiplier if the kernel performance governor doesn't do so properly? There are times where I really would like the 3.6 GHz to just sit there, for long video encodes, or live streams.
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Roman_Gruber
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Joined: 03 Oct 2006
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PostPosted: Thu Oct 16, 2014 10:03 am    Post subject: Reply with quote

Are you sure the readings from these programs are correct? do not get me wrong but there could be read out conversation bugs in them.

aFAIK turbo boost only occurs on certain circumstances? how do you ensure these circumstances to happen and how do you measure correct the values?

Quote:
Is there a way to manually set the multiplier if the kernel performance governor doesn't do so properly?

AFAIK you need a mod bios with mod motherboard. usually the bios are locked and cleaned out of those overclock features.
AFAIK no software for overclocking in GNU / Linux

and I assume you talk about the random turbo boost and this is for sure handled in teh cpu when intel thinks it is safe to overclock it. so i doubt you can influence it.

you may hardwire the FSB on your mobo but thats not an easy task (and therefore not an option)

AFAIK thermal stress has to be low + only one cpu core / hyperthreading core 1 or 2 have to be used that the cpu overclcoks to the max. so how do you ensure the gnu linux kernel only uses one core of your cpu?

the magic of those windows overclocking apps is well hidden and never revealed. other apps are from the board makers itself and also no source code / how it works available. usually you need fsb / ++ other mainboard related set things to improve / overclock ...
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krinn
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PostPosted: Thu Oct 16, 2014 12:43 pm    Post subject: Reply with quote

You mistake the two features : one is to handle the freq of the cpu with a power saving / energy eaten result in mind (the freq scaling) ; the other is a feature to max out your cpu performance when not fully in use, when not all your cores are working it increase the freq multi value of the running cores to boost the cpu (turbo boost)

It's even worst (for me, as a guess, as i really don't know if it's true), but assuming one use the freq scalling to lower energy consume by the cpu should just disable the turbo boost (that by essence is against the first aim of the other feature)

So in order to see your cpu boost in action, you have to only use few cores (the lower the better), and there's are fixed settings for that, if one core is in use it will certainly do 3.6 but when just 2 are in use it will do something lower than 3.6.

If you want to see your cpu boost settings use i7z (yes in portage) or run a non multi-cores kernel to force one core only.
edit: oh just saw you know i7z already, don't know how you miss it gave you the settings...
sample from my cpu : Max TURBO Multiplier (if Enabled) with 1/2/3/4 Cores is 25x/24x/24x/24x (and it can be read as to get max 25x multi i must use 1 core only, else i get down to 24x)
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thender
Tux's lil' helper
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Joined: 26 Aug 2013
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PostPosted: Thu Oct 16, 2014 5:19 pm    Post subject: Reply with quote

I learned something. Thank you!
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Anon-E-moose
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Joined: 23 May 2008
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PostPosted: Thu Oct 16, 2014 5:41 pm    Post subject: Reply with quote

2.9 is the normal speed, you will get 3.6 in turbo mode with certain conditions.

The motherboard usually needs to be set to allow turbo (at least all the amd one's I've seen work that way)
To run at 3.6 the cpu will shut down from 4 threads to 2 (a guess given the way turbo mode works) or maybe even one core.
You can't set it to run at 3.6 that's something that the mb/cpu will decide given some conditions.

You're better off with 4 threads @ 2.9 vs 1 or 2 @3.6
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