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64 Bit Linux shows 4GB... was Using all of 4GB RAM...



Dennis Gilmore suggested that I boot a 64 bit Live CD to see what it
said about memory usage.  So I did:

[fedora localhost ~]$ free -m
             total       used       free     shared    buffers
cached
Mem:          3969       1286       2682          0        143
827
-/+ buffers/cache:        315       3654
Swap:         1992          0       1992

Here is what it looks like under my 32 bit installation:

$ free -m
             total       used       free     shared    buffers
cached
Mem:          3034        978       2055          0         33
619
-/+ buffers/cache:        326       2708
Swap:         1992          0       1992

I appear to gain 935MB of RAM running the 64 bit version.  This is in
spite of the spec sheet on my laptop saying:

"Memory 4096 MB Memory Max Up to 4GB DDR2 (Up to 1 GB may not be
available due to 32-bit operating system resource requirements)"

This message probably means to say that the memory is available above
the 4GB address limit of 32 bit programs and that 32 bit applications
can't access it.  But its there for 64bit applications to use because it
probably gets remapped above the 4GB boundary and 64 bit applications
can address it there.

The only difference between the two tests is that with the 32bit
installation I am running 2 1680x1050 monitors side by side, whereas
with the 64 bit test both monitors were running but they were displaying
the same thing.  I don't think this makes a difference in the amount of
memory available because I ran it earlier in the week without the 2nd
monitor and it still showed it was only using 3GB.

It looks like the 64bit version of Linux makes use of all the available
RAM, whereas the 32bit version only uses the first 3GB.

So... what is the easiest way to convert my 32 bit installation to 64
bits ?  Please don't tell me to reinstall because I just did that
earlier this week to go from F9 back to F8.

Thanks


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