is dual core = multi processor?

I am a software developer working on a program in which I am about to
introduce threads. The more the processors, the better. In years
past I learned the hard way that running on a hyperthreaded box verse
a true multithreaded box gives you very different results, at times.
Am I going to get yet a thrid type of results from running on a dual
core machines or is it really the same things, for my purposes, as a
multi threaded box?

"Cartoper" <cartoper@gmail.com> wrote in message
news:1194008291.345862.149980@50g2000hsm.googlegro ups.com...
>I am a software developer working on a program in which I am about to
> introduce threads. The more the processors, the better. In years
> past I learned the hard way that running on a hyperthreaded box verse
> a true multithreaded box gives you very different results, at times.
> Am I going to get yet a thrid type of results from running on a dual
> core machines or is it really the same things, for my purposes, as a
> multi threaded box?

Dual core is 2 separate cores. They may or may not be on the same die -
multiprocessor as opposed to multi-core, but they are 2 CPUs with their own
cache and pipeline. Hyperthreading is a technology that uses the idle cycles
of a processor to create a virtual CPU. it will appear as 2 processors, but
can only run 1 thread at a time. With multi-core / multi-processor you are
going to need critical sections and deadlock handling.

On Fri, 02 Nov 2007 05:58:11 -0700, Cartoper
<cartoper@gmail.com> wrote:

>I am a software developer working on a program in which I am about to
>introduce threads. The more the processors, the better. In years
>past I learned the hard way that running on a hyperthreaded box verse
>a true multithreaded box gives you very different results, at times.
>Am I going to get yet a thrid type of results from running on a dual
>core machines or is it really the same things, for my purposes, as a
>multi threaded box?


Yes, dual core (AKA Core2Duo or Athlon X2?) is really two
processors fully capable of using two threads independently
as if it were two discrete processor *modules*.

In message <41lni3d7g2v0vio6ukj0jjnah4rrg424ei@4ax.com> kony
<spam@spam.com> wrote:

>On Fri, 02 Nov 2007 05:58:11 -0700, Cartoper
><cartoper@gmail.com> wrote:
>
>>I am a software developer working on a program in which I am about to
>>introduce threads. The more the processors, the better. In years
>>past I learned the hard way that running on a hyperthreaded box verse
>>a true multithreaded box gives you very different results, at times.
>>Am I going to get yet a thrid type of results from running on a dual
>>core machines or is it really the same things, for my purposes, as a
>>multi threaded box?
>
>
>Yes, dual core (AKA Core2Duo or Athlon X2?) is really two
>processors fully capable of using two threads independently
>as if it were two discrete processor *modules*.

And better, AMD's crossbar technology allows the cores to communicate
directly, so caching tends to be more efficient on a dual-core rather
then dual-CPU implementation (assuming total cache sizes are the same)

--
You can get more with a kind word and a 2x4 than just a kind word.

Somewhere on the interweb "DevilsPGD" typed:
> In message <41lni3d7g2v0vio6ukj0jjnah4rrg424ei@4ax.com> kony
> <spam@spam.com> wrote:
>
> > On Fri, 02 Nov 2007 05:58:11 -0700, Cartoper
> > <cartoper@gmail.com> wrote:
> >
> > > I am a software developer working on a program in which I am
> > > about to introduce threads. The more the processors, the better.
> > > In years past I learned the hard way that running on a
> > > hyperthreaded box verse a true multithreaded box gives you very
> > > different results, at times. Am I going to get yet a thrid type
> > > of results from running on a dual core machines or is it really
> > > the same things, for my purposes, as a multi threaded box?
> >
> >
> > Yes, dual core (AKA Core2Duo or Athlon X2?) is really two
> > processors fully capable of using two threads independently
> > as if it were two discrete processor *modules*.
>
> And better, AMD's crossbar technology allows the cores to communicate
> directly, so caching tends to be more efficient on a dual-core rather
> then dual-CPU implementation (assuming total cache sizes are the same)

Whereas Intel's Core2 Duo/Quads have shared L2 cache so that either/any core
can access data in the cache instead of having to load it into a discrete
cache first a'la AMD. <g>
--
TTFN

Shaun.

In message <fgivke$7vb$1@registered.motzarella.org> "~misfit~"
<misfit61nz@yahooligans.co.nz> wrote:

>Whereas Intel's Core2 Duo/Quads have shared L2 cache so that either/any core
>can access data in the cache instead of having to load it into a discrete
>cache first a'la AMD. <g>

AMD did it first though, which is why I used them as an example.
Pentium-Ds of the same era fell back to FSB speeds to move data between
the CPUs, whereas AMD CPUs were doing it at CPU speed.

Intel did it better. That's often been the case.

--
You can get more with a kind word and a 2x4 than just a kind word.

Somewhere on the interweb "DevilsPGD" typed:
> In message <fgivke$7vb$1@registered.motzarella.org> "~misfit~"
> <misfit61nz@yahooligans.co.nz> wrote:
>
> > Whereas Intel's Core2 Duo/Quads have shared L2 cache so that
> > either/any core can access data in the cache instead of having to
> > load it into a discrete cache first a'la AMD. <g>
>
> AMD did it first though, which is why I used them as an example.
> Pentium-Ds of the same era fell back to FSB speeds to move data
> between the CPUs, whereas AMD CPUs were doing it at CPU speed.
>
> Intel did it better. That's often been the case.

Ahhh, okay, thanks for that. I'd deliberately avoided reading about
dual-core CPUs until recently as I didn't want to tease myself with what I
couldn't afford.

However, after selling my old Barton and nForce2 Ultra mobo on <local
version of eBay> and buying a mobo that allowed me to use my existing DDR
RAM and AGP card I've just "got into the scene" so to speak. Running an
E4500 on a "1066" FSB for 2.93 GHz. :-)
--
TTFN

Shaun.