SMP/dual (multi) core phase II

[Daniel Feenberg]

On Mon, 7 May 2007, Derek Atkins wrote:

> Daniel Feenberg <feenberg at nber.org> writes:
>
>> We have tested quad core and dual core Intel core 2 duo processors doing
>> statistical calculations (long float arithmetic, mostly) and found the
>> quad core runs 4 independent processes at just about the same speed (each)
>> as 2 dual core processors of the same clock rate run them. So no advantage
>> seen to more sockets, only cores and clock rates count. None of the
>> processes is multi-threaded.
>>
>> Our little compute cluster ended up with 3 quad core motherboards and 1
>> double socket dual core. All 4 machines have nearly the same capacity.
>> This could be an artifact of floating point, we haven't tested other load
>> types.
>
> Have you tested memory-intensive tasks and whether you get
> more memory bandwidth in a quad-core or 2x dual-core?  Have
> you compared Intel to AMD for memory throughput?   I don't
> know your application so I don't know if it's memory bound or
> CPU bound.

As the "long float arithmetic" description implies these are compute bound 
processes, although the memory space used is far larger than the cache. 
Think of calculating the dot products of thousands of two million element 
vectors.

>
>> Daniel Feenberg
>
> -derek
> --
>       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
>       Member, MIT Student Information Processing Board  (SIPB)
>       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
>       warlord at MIT.EDU                        PGP key available
>


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