Maximum Memory in Linux

Is there a theoretical or functional maximum memory you can put in a
Linux machine? I have a server with 2GB installed but the free command
stubbornly says:

# free
             total       used       free     shared    buffers
cached
Mem:        902768     672416     230352          0      45820
193564
-/+ buffers/cache:     433032     469736
Swap:       522216      25124     497092

This is Red Hat Linux 9 machine with a stock kernel. Am I missing some
crucial point? Has anyone else dealt with a lower than expected
reported memory?

Thanks,

Brian