Le 14/11/2014 00:36, Cousin Ricky a écrit :
> Le_Forgeron <jgr### [at] freefr> wrote:
>> On 13/11/2014 21:21, Cousin Ricky wrote:
>>> My hardware is a Dell Inspiron 17R with Intel Core i7 (8 cores).
>>
>> Isn't that 4 cores with HT ? (for povray, it would be worth 5 cores, YMMV)
> 
> I've seen "quad core" in literature not attached to this particular model, but
> in the POV-Ray statistics, there is a clear 8-to-1 ratio between CPU times and
> elapsed times.  Does this mean that there are 2 CPUs in each core?
> 
> 
Sort of... there is two full set of registers in each core, allowing to
run two code in parallel... as long as they do not need the same
resources from the core.

at 100% cpu like povray, yes there is a 8:1 ratio between cpu times and
wall-clock time. Yet, if the scheduler of the operating system is not
too bad, if you force povray to run on less threads (with -WT<number>
option), you can get some surprise like -WT8 is not twice faster that -WT4.

With good schedulers, povray -WT4 would run one thread per core, leaving
the other set of registers idle or used by something else.


-- 
Just because nobody complains does not mean all parachutes are perfect.

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