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HPUX, Poulson processor variable speed?

 
effarement
Occasional Visitor

HPUX, Poulson processor variable speed?

All,

 

I just wanted to check 3 things, but have been unable to get the info by myself.

 

- Itanium Poulson supports variable frequency (speed stepping): true or wrong?

- If true, does HPUX provides support for this?

- If true is there a way to get / fix  the frequency either through command line or programmatically? I believe machinfo gives me the maxiumu speed, rather than th ecurrent one).

 

Thanks in advance for any hint

 

François

1 REPLY
Matti_Kurkela
Honored Contributor

Re: HPUX, Poulson processor variable speed?

Wikipedia says that all Itanium Poulson models support Turbo Boost and Enhanced Intel Speed Step (EIST).


Turbo Boost means that if only one or two cores are being used, those core(s) can run with higher clock speed than when all the cores are in use. Running all cores simultaneously with maximum boost would destroy the processor in a thermal meltdown.

 

At least in the Linux/x86 world, the current understanding seems to be that the most efficient overall strategy is to run at maximum speed whenever there are instructions to be executed. When there is nothing to do, the most efficient strategy is to idle or power down as many cores as possible. All this happens thousands of times per second, in a mostly automated fashion at the hardware level. Humans are simply not fast enough to control the frequency manually to get anywhere near the maximum efficiency. Even programmatic control is slower than built-in hardware features.

 

I would expect that HP-UX has at least some minimal support for these features, if only to make it easier to build high-density servers (more efficient processors = less heat to get rid of). I don't think there is a tool for the regular HP-UX admins for adjusting the system behavior at that level; if there was a support tool for that, I would guess that it would come with dire warnings ("misuse of this tool can cause overheating and hardware damage!").

MK