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Can 1 processor access all 16 gigs of memory on server MB? - Printable Version

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Can 1 processor access all 16 gigs of memory on server MB? - jbl5764801 - 05-29-2014 09:26 AM

I have an application which requires large amounts of memory, so I am considering buying a server motherboard with support for up to 16 or maybe 32 gigs of ram. Almost all server motherboards have a dual CPU configuration, but I want to keep the system as cheap as possible. Hence, I only want to buy 1 CPU. Will that 1 CPU be able to access all the memory on the machine, or just half?

Suppose I buy a cheap 2nd processor. Will a single threaded program be able to access all the memory? Will the program context temporarily change to the other processor when requesting certain memory addresses? What sort of performance hit is usually observed with such a scenario? Thanks!


- Charlie - 05-29-2014 09:29 AM

ay.. u worry too much... use one processor and put a ram as big as u can . 32gigs and when u get more pocket mula, get a second processor if u think u need it.
if all works and ur happy with it, what do u care about the so called 'performance hit'.


- Brian F - 05-29-2014 09:38 AM

The number of processors has nothing to do with how much memory the system can access.

To access more than 4GB of ram, the processor must be 64 bit (ALL Intel and AMD "PC" CPU's from the last 2 years are...), AND the operating system must be a 64 bit operating system, AND the program you are running must be compiled as a 64 bit program.

If you are running windows, a 32 bit program or driver at any point in the chain, will limit that program to 3-3.5 GB of ram. For example, you have a 64 bit CPU, running 64 bit windows, but your program is 32 bit (almost all of them). Your operating system could access 16GB of ram, but the program (let's say a graphics processing program) would STILL be limited to less tha 4GB of ram available to the program itself.

If you are running linux/bsd etc. This isn't a problem, just install the 64 bit version of the linux distro you choose, install the 64 bit version of the program you want to run, or compile it on the 64 bit system, and you will be able to access as much memory as your server can accept. (Actually more memory that you can afford to buy, there are NO motherboards that can accept as much memory as a 64 bit CPU/OS combo can physically access... not even close... It will be a LONG LONG time (if ever) before a system comes along that can accept enough memory in it to necessitate a 128 bit cpu.