Dual Core Or Dual CPU - What's the real difference in performance?

Jerry McAllister jerrymc at msu.edu
Thu Feb 8 13:35:58 UTC 2007

On Wed, Feb 07, 2007 at 07:22:26PM -0800, Garrett Cooper wrote:

> Andrew Hammond wrote:
> >On 2/7/07, Nicole Harrington <drumslayer2 at yahoo.com> wrote:
> >> Hello all,
> >> I have been building/using servers that were dual CPU
> >>AMD Opteron systems for some time.  (usually 246
> >>Opteron cpu's)
> >>
> >> Now of course the world is shifting to Dual Core.
> >>
> >>Using FreeBSD, what is really the difference, besides
> >>power and ability to shove in more memory, between
> >>having the two seperate CPUS's?
> >
> >Well, you also have two additional HT buses for memory access. And one
> >additional HT bus for peripheral access although most motherboard
> >manufacturers don't actually do anything with it.
> >
> >> What if I did 2, Dual Core cpu's? Would the SMP
> >>overhead and sharing to a [Giant Locked] disk and or
> >>network erase any benefits?
> >
> >Benefits to what? Your computer can idle quite effectively with a 386
> >processor while consuming less power, producing less heat and
> >requiring much less capital outlay than any Opteron box.
> I'm not sure where you got that info, but for the Pentium processor line 
> at least, you're MUCH better off getting a Core Duo compared to the 
> Pentium 4 HT enabled equivalent.

I think you took his intended humor too seriously.
His point really was that the poster did not indicate what
the system would be used for and thus it was not really 
possible to say much about the benefit.  If the system was
mostly sitting idle, one CPU is about the same as another CPU
in so far as what it gets done.   But if it has a load that
distributes well over dual cores, then it makes a very big difference.


> Intel's power system (at least at the hardware level) is pretty good 
> about shutting down cores when not in use, and actually it's better 
> power wise to get a dual core processor compared to a dual processor 
> machine, since on a dual processor machine both processors are fired up 
> at the same time.
> Besides, with dual cores it's a shorter path electrically core to core, 
> compared to a processor. The only OS that actually performs better with 
> a dual single core processor setup compared to a single dual core 
> processor would be Mac OSX (believe it or not). But that's because they 
> use a mach kernel instead of a monolithic kernel like FreeBSD, Linux, 
> and Windows.
> Look up previous discussions on this list for the mach kernel and OSX if 
> you're curious, or just look up the article on wikipedia.
> -Garrett
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