[LCP]Single threaded programs and 32GB RAM/Quad Opteron question

[Buddy Lumpkin]

Not only can the 64-bit platform running on a 64-bit kernel address the
entire 32GB of physical memory from within the kernel or user address space;
but in addition, you do not need any of the special huge-mem, bigmem, or
large memory kernels since they all imply lots of hacks to a 32-bit kernel
to use larger address spaces.

Just install and go.

--Buddy

-----Original Message-----
From: linuxcprogramming-admin at lists.linux.org.au
[mailto:linuxcprogramming-admin at lists.linux.org.au] On Behalf Of Carlos J.
Cela
Sent: Sunday, September 12, 2004 4:48 PM
To: linuxcprogramming at lists.linux.org.au
Subject: [LCP]Single threaded programs and 32GB RAM/Quad Opteron question

Hi,

I have been working for the last year developing software for a research 
project which involves large simulations. So far we have been using 
Pentium 4 based PC's with 4GB of RAM. As it is getting harder and harder 
to fit our more detailed models in 4GB of memory, we are planning on 
purchasing a quad-Opteron PC with 32GB, running probably Fedora Core 2, 
large mem kernel.

Reading hardware specs, I have noticed that one can only install 32GB 
RAM if there are 4 processors installed in the machine....do you guys 
know if in a 32GB RAM/Quad Opteron system a program running in just one 
of the processors can access the full range of memory?

I mean, if my application is single-threaded...can I use the 32GB od RAM 
or just to 1/4th of it? is all or part of the memory shared? if so, why 
the '4 processors installed' requirement? are there any other specifics 
that I should be aware of when writing software for such system?

Have any of you guys have experience with similar setups? Any 
help/advice will be appreciated.

Thanks,
Carlos-


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