UCS BIOS advise

Answered Question
Sep 14th, 2012

Hello,

I've seen there's recently been uploaded a document with BIOS config reccomendations for UCS in:

http://www.cisco.com/en/US/prod/collateral/ps10265/ps10281/whitepaper_c07-614438.html

One of the points states: "if you want the best performance at a utilization rate of less than 90 percent, you should disable Intel SpeedStep".

I've checked the Default BIOS config setting of IntelSpeedStep and TurboBoost in UCS B-200 M2/M3, and it is ENABLED.

Taking into account that most of the production environments should run under 90% of CPU load, I'm trying to figure out WHY are these features enabled by default???

Or maybe the question should be: is the BIOS Settings reccomendations white paper mentioned above partially wrong?

Thanks,

I have this problem too.
0 votes
Correct Answer by roberbur about 1 year 6 months ago

It makes sense to me...

By default we enable speedstep - which allows for a more power effecient operation.

The paper says if you require:

-Best performance

and

-Utilization is <90%

Then you can disable steedstep (which makes the CPU run at full speed/power.  I think you're not understanding what "disabling" speedstep does.  Disabling speedstep makes the CPU work harder.  Enabling it allows it to clock DOWN.

Regards,

Robert

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roberbur Fri, 09/28/2012 - 05:54

Dani,

Intel Speedstep allows a CPU to be clock down and therefore save power.  Any system where the CPU usage is above 90% will likley be running at full clock speed regardless if Speedstepping is enabled or not hence the comment in the whitepaper.  If you require the best performance, you can disable it which will always force the CPU to remain at full speed (therefore using more power).  In UCS we leverage speedstep so UCSM can manage C-states of the system and therefor control the power policy of the system and implement power-capping.

It's similar to memory performance mode on dual voltage DIMMs.  In power-saving mode it runs the memory at a lower speed and lower voltage.  In performance mode it runs the memory at the highest frequency and uses more power.

Regards,

Robert

dani_bosch Mon, 10/01/2012 - 01:20

Robert, the whitepaper says exactly the opposite of what you say. Hence my doubts.

You say one should disable SpeedStep when running at MORE than 90% CPU, whereas the white paper reccomends to disable it when working at LESS than 90%

What's wrong here?

Correct Answer
roberbur Mon, 10/01/2012 - 05:12

It makes sense to me...

By default we enable speedstep - which allows for a more power effecient operation.

The paper says if you require:

-Best performance

and

-Utilization is <90%

Then you can disable steedstep (which makes the CPU run at full speed/power.  I think you're not understanding what "disabling" speedstep does.  Disabling speedstep makes the CPU work harder.  Enabling it allows it to clock DOWN.

Regards,

Robert

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Posted September 14, 2012 at 2:10 AM
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