[dba-Tech] Duo-core processors

Josh McFarlane darsant at gmail.com
Fri Sep 15 11:18:17 CDT 2006


Not quite true.

The OS sees it as two logical CPUs and assigns tasks as such. You can
go into task manager and assign to one CPU or another. However, for
hardware requirements, Windows by default treats it as a
"hyper-threading" processor - IE you can run 4 'true' cores within XP,
which has a physical processor cap of I think 2 IIRC. The AMD Dual
Cores at least have an expanded identification that signifies them as
dual cores, and not just hyper-threaded. This is recognized by newer
versions of Windows and other OS's, but is backwards compatible,
appearing as the HyperThreaded processor to OSes using the old ID
format.

SQL Server should recognize it as two seperate logical CPUs - Visual
Studio will shoot builds off to both cores seperately if you have the
latest version. However, I've never used SQL Server, so Microsoft may
have it set up seperately.

In general, if a program enumerates the available CPUs, they will see
CPU 0 and CPU 1 available on a single dual core machine. You can force
thread affinity to one or the other, but in general Windows will
optimize thread affinity for you. ASAIK, there is no different
addressing for RAM, it's just allocated from the global pool. Windows
might do optimizing under the hood, but a pointer to memory is the
same without regard to which processor you're sitting on.

Josh

On 9/15/06, Jim Moss <jim.moss at jlmoss.net> wrote:
> Dual core processors are seen by the OS as 1 CPU
>
> > This may be stupid questions (or in the immortal words of The Simpsons,
> > there are no stupid questions, only stupid people). But I digress.
> >
> > Is a duo-core CPU viewed by such processes as SQL 2005 as 2 CPUs? And
> > assuming that it is, and further assuming that there are 2GB of RAM
> > aboard, how does the system decide which vcpu gets how much RAM? In
> > particular, I was thinking about parallel queries in SQL.
> >
> > TIA,
> > Arthur
> >
> >
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> >
>
>
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-- 
Josh McFarlane
http://www.joshmcfarlane.com
"Peace cannot be kept by force. It can only be achieved by understanding."
-Albert Einstein



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