tightly-coupled Grid

Hello,

Could anyone explain why you guys call 9grid as
tightly-coupled grid on
http://public.lanl.gov/cluster/projects/index.html#9grid?
I read the paper on 9grid website, but I'm not quite
sure about it. Does the "tightly-coupled" Grid means a
Grid which doesn't need add-ons of OS?

Thanks,
-Bo


		
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