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

[Craig White]

On Wed, 2008-10-01 at 13:56 -0400, Linuxguy123 wrote:
> Dennis Gilmore suggested that I boot a 64 bit Live CD to see what it
> said about memory usage.  So I did:
> 
> [fedora at 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.
----
sorry - reinstall is your only option

Craig