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Re: Fedora 9 32 or 64 Bit - Which One?

Alan Cox wrote:
On Mon, 27 Oct 2008 11:54:47 -0400
Matthew Flaschen <matthew flaschen gatech edu> wrote:

Alan Cox wrote:

The moment you have more than about 900MB of RAM there are big advantages
to running a 64bit kernel as it can keep all of physical and virtual
space mapped at the same time, which is a big performance win.


Wouldn't you need twice as much memory to have the same memory for applications if you are using double the word size?

Or does the OS somehow take that into account and split the 64 bit words into their components to get most efficient use out of them?

To clarify, I have 2 GBytes of memory in a 32 bit OS. If I use a 64 bit OS, isn't that memory now effectively halved? The same as if I use 16 bits to store a character instead of 8 bits. It is my understanding that UTF-8 only uses the second 8 bits if it needs it. So that is like my second question, making sure that there isn't lots of empty memory.

Thanks for any clarification you can offer.

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