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Core i5 2400S not overcloking to TPU plan

post #1 of 5
Thread Starter 
A have an Asus P8Z68 Deluxe MB and Core i5 2400S 2,5 GHz CPU. Just by hitting the TPU key i can auto-overclock my CPU to 3811 MHz in fashion of 37X 103 MHz. This is also the maximum OC i can achieve with manual OC as i have tried playing with voltages a bit...

3,8 GHz would be just fine, however...

For some reason the CPU actually overclocks to pathetic 30X 103 MHz and the 7X multiplier is somehow "chomped away". This is really DS annoying, because i have disabled these:

1) SpeedStep
2) C1,C31 C6
3) Virtualization

Where is my 37X multiplier? I just don't understand WTH is wrong with the 30X picture...
Edited by Marshock - 10/5/13 at 2:30pm
post #2 of 5
On the non-K processors, to achieve maximum turbo boost, unused cores have to be able to enter the C3 or C6 low power state. You probably need to enable at least C3. There is also no need to turn off SpeedStep. The bios in some motherboards will ignore your selection when you turn this off and they will enable it in the background anyhow. Turn it back on until you figure out what is going on.

http://ark.intel.com/products/52208/Intel-Core-i5-2400S-Processor-6M-Cache-up-to-3_30-GHz

The maximum turbo multiplier for this CPU is 33 and this CPU also supports a +4 multiplier overclock. That gives you a 37 multiplier but this is only available when a single core is active. You won't be able to run the 37 multiplier when all 4 cores are active. You also can not disable SpeedStep and lock this CPU to the 37 multiplier. Your 2400S is not a K series CPU so they are limited.

http://ark.intel.com/products/52207/Intel-Core-i5-2400-Processor-6M-Cache-up-to-3_40-GHz

The other problem is that a 2400 has a 95W TDP. A 2400S is a low power CPU with a 65 watt TDP. When overclocking, if power consumption exceeds the rated TDP, the amount of Turbo Boost will automatically be reduced so your multiplier might decrease for this reason when your CPU is heavily loaded with Prime95 or Linpack testing.

Give ThrottleStop a try if you want to learn some more about the power limits and multiplier limits that Intel built into your 2400S. Either of the two programs listed will show you what C States are enabled when you are getting your 37 multiplier. Post some screen shots so I can have a look.

ThrottleStop 6.00
http://www.thedigitalhq.com/downloads/download-info/throttlestop-6-00/
Edited by unclewebb - 10/5/13 at 6:51pm
post #3 of 5
Thread Starter 
Quote:
Originally Posted by unclewebb View Post

On the non-K processors, to achieve maximum turbo boost, unused cores have to be able to enter the C3 or C6 low power state.


Right. Done. 3811 MHz is now achievable. So only the K series processors can utilize all of their cores to the maximum turbo boost frequency equally?
Quote:
Originally Posted by unclewebb View Post

The other problem is that a 2400 has a 95W TDP. A 2400S is a low power CPU with a 65 watt TDP. When overclocking, if power consumption exceeds the rated TDP, the amount of Turbo Boost will automatically be reduced so your multiplier might decrease for this reason when your CPU is heavily loaded with Prime95 or Linpack testing.

There is a setting in Asus BIOS to increase something like a CPU power output to 140 %. Would this help prevent the loss of turbo boost in case of increased power consumption?


Also, i see the multiplier jumping to 3811 MHz from time to time, but when i load Crysis 3 in window mode, it only goes up to 3 GHz. Is there a parameter to write in the target line of game.exe shortcut file to enable the CPU to go max throttle?
Edited by Marshock - 10/6/13 at 3:43am
post #4 of 5
Quote:
Originally Posted by Marshock View Post

So only the K series processors can utilize all of their cores to the maximum turbo boost frequency equally?

Generally speaking, the above is true. Intel makes so many different CPUs that there might be some exceptions so lets talk specifically about your CPU.

As I mentioned before, a Core i5-2400S is marketed by Intel as a low power CPU with a reduced TDP rating. Part of this reduced TDP rating might be because Intel hand picks the low voltage CPUs on the assembly line but most of this is achieved because Intel lowered the maximum multipliers which lowers the maximum speed and power consumption.

Here is a 2400 vs 2400S comparison:

Maximum Multipliers

Core i5-2400
4 core: 32
3 core: 33
2 core: 33
1 core: 34

Core i5-2400 + 4 bins of overclocking
4 core: 36
3 core: 37
2 core: 37
1 core: 38

Core i5-2400S
4 core: 26
3 core: 28
2 core: 32
1 core: 33

Core i5-2400S + 4 bins of overclocking
4 core: 30
3 core: 32
2 core: 36
1 core: 37

You need C3 or C6 enabled to achieve these maximums. The way these CPUs work is that as more cores become active, the maximum multiplier decreases. A regular Core i5-2400 can run with all 4 cores active and use a 36 multiplier while an overclocked 2400S is limited to the 30 multiplier when all 4 cores are active. It will only be able to achieve this maximum if the CPU is running below the TDP limit. The 2400 has a much higher TDP limit so it should have no problem staying under that limit while the 2400S is going to be a lot closer to its 65W limit when stressed out with Prime95 or Linpack. If this is the case, the maximum multiplier will drop further in the 2400S.
Quote:
There is a setting in Asus BIOS to increase something like a CPU power output to 140 %. Would this help prevent the loss of turbo boost in case of increased power consumption?

You would have to do some testing to find out. If you increase the core voltage, this can increase the power consumption and this could trigger turbo throttling sooner which is the opposite of what you are trying to accomplish. If this bios adjustment raises the TDP power limit then yes, that would help if you are presently reaching the 65W limit. If you are not reaching this limit then that bios setting won't make any difference.
Quote:
Also, i see the multiplier jumping to 3811 MHz from time to time, but when i load Crysis 3 in window mode, it only goes up to 3 GHz.

Are you using CPU-Z? It has been designed as a MHz validation tool. The multiplier in these CPUs can be changing hundreds of times a second so at times the data CPU-Z shows is too general to get a good understanding of what your CPU is really doing internally. Post some ThrottleStop screen shots while testing with Prime95 or turn on the Log File option in ThrottleStop so you have an accurate record of what your CPU is really doing while gaming. You can Copy and Paste log file data to www.pastebin.com and then post a link here if you want me to have a look.
Quote:
Is there a parameter to write in the target line of game.exe shortcut file to enable the CPU to go max throttle?

30 is the absolute maximum multiplier available when 4 cores are active. This is hard coded into these CPUs by Intel at the factory and there is no way around this limitation.
post #5 of 5
Thread Starter 
Well thanks for the detailed reply! Excellent stuff!

Looks like the only Core i5 CPU on active sale with the K letter is the 3570K - there have been no K series Core i5 processors produced except 3570K it seems, so looks like i am going to get that one, otherwise the motherboard's oc capabilities will be wasted.
Edited by Marshock - 10/8/13 at 12:22pm
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