More RAM for buffers?

[Kirk Strauser]

I have an AMD system with 6GB of RAM.  From dmesg:

    usable memory = 6428237824 (6130 MB)
    avail memory  = 6203797504 (5916 MB)

However, most of it is just sitting there when it looks like it could be 
used for buffers or cache:

Mem: 1186M Active, 3902M Inact, 468M Wired, 233M Cache, 214M Buf, 138M Free
Swap: 8192M Total, 900K Used, 8191M Free

Since I've yet to find a great explanation for what the different types of 
memory are, could someone say why all that inactive memory is better than 
using it for cache or buffers?
-- 
Kirk Strauser