Re: single core high performance computing/max memory?
- From: Aragorn <aragorn@xxxxxxxxxxxxxxxxxxx>
- Date: Tue, 01 Jul 2008 03:08:55 +0200
On Monday 30 June 2008 12:35, someone who identifies as *Chris* wrote
I'm looking for a high performance computing environment for genetic
analysis. As far as I understood, as well Opterons as Xeons can only
address 4GB of main memory per core. Is this right?
Opterons are 64-bit processors with an on-chip memory controller, common to
all cores on the chip. It's got 40 bits for RAM, so you do the math
yourself. ;-) When multiple Opterons are installed on a motherboard, then
each Opteron has its dedicated memory controller and dedicated memory. All
processors can see all memory in the machine, but will tend to use the
memory that's "closer" to the processor. It's called ccNUMA
(cache-coherent Non-Uniform Memory Addressing). ;-)
I have a dual-Opteron machine with two dualcore Opterons. It's got 32 GB of
ECC registered DDR-2 memory installed, and all is recognized.
Xeons come in two variants: 32-bit and 64-bit. Both use a memory controller
on the motherboard for all cores and all processor sockets in the machine,
so it's actually an SMP machine and not a NUMA. 32-bit machines are
limited to 4 GB - or 64 GB in paged mode if PAE is enabled in the kernel,
which does however require that the kernel be compiled for i686 at the
least, because i586 (i.e. Intel Pentium and Pentium MMX, AMD
K5/K6/K6-II/K6-III) does not have PAE yet - but the 64-bit Intels have the
same RAM and virtual memory capacity as their AMD counterparts.
(registered GNU/Linux user #223157)
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