Ubuntu :: Karmic (amd64) - Memory Usage Never Exceeds 1gb?

Currently I have one instance of Avidemux indexing a 16GB mpeg2 file, another instance of Avidemux transcoding a 4.7GB mpeg2 file into an 860MB mpeg4 (by two pass encoding with fully exhaustive motion detection, extra quality filters, and a wide VBR range), vlc playing a DVD-quality avi, totem playing a DVD-quality ogm, and I'm capturing video from a pvr card.. With compiz managing the desktop (with all the most disgusting eyecandy on: wobbly windows, Atlantis, desktop sphere, experimental plugins from git, etc).My processor (3GHz Athlon x2) is completely maxed out of course... but I can't seem to raise the memory usage over "1.2GiB (16%) of 7.8 GiB"Is that normal? Is there something else I could do to test my memory capacity? (as in really usefulapplications, not just benchmarks)?Alternatively, if karmic is never going to use the rest of that memory, I might opt to run some parts of the desktop environment and/or kernel from a ramdisk.