Pentium 805D has an interesting surprise
Jarod Wilson
jarod at wilsonet.com
Wed Apr 25 15:04:43 EDT 2007
On Wednesday 25 April 2007 13:56:35 Ben Scott wrote:
> On 4/25/07, Thomas Charron <twaffle at gmail.com> wrote:
> > Yes, this is exactly why I say the differences from a software
> > perspective are debatable.
>
> In the sense of what you have to program to make use of it, yes.
> Either way, you have to worry about shared memory concurrency,
> locking, re-entrance, all that stuff. But the performance
> characteristics are quite different.
>
> Dual core and quad core is just SMP (symmetric multi-processor)
> implemented in a single IC package. It used to be this was done at
> the motherboard level -- two sockets, two IC packages, and special SMP
> chipsets. Dual core just fits everything into a single IC package,
> and makes the SMP chipset standard. A single dual-core processor is
> "exactly" the same thing as a conventional dual processor system.
>
> (I put "exactly" in quotes because there are some differences. For
> example, I understand some cache sharing is possible on some chips.
> But it's really really really close to classic x86 SMP.)
There's another big difference in the AMD64 world that should be noted. Since
the memory controller is on-chip, a multi-socket opteron system winds up
being NUMA-capable (multiple independent memory controllers and banks of
dimms directly accessible by a specific socket), whereas a
single-socket/multi-core opteron/athlon64 isn't NUMA-capable, all cores share
direct access to the same memory.
--
Jarod Wilson
jarod at wilsonet.com
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