The dell_rbu driver in this kernel version has a bug that drives the CPU load up to 1. It has already been patched by the author. Details from LKML here: http://lkml.org/lkml/2006/1/13/201
Fixed in gentoo-sources-2.6.15-r3 (genpatches-2.6.15-6)
*** Bug 122398 has been marked as a duplicate of this bug. ***
Also fixed in hardened-sources-2.6.14-r6 (genpatches-2.6.14-11).