As you may or may not be aware - there appears to be an issue in 3ds max r7 and r8 where certain components leave the 3ds max state set incorrectly - causing one or more of the CPUs in a machine to fluctuate in performance.
This tends to affect elements of 3ds max and third party plugins which are highly threaded; Brazil r/s is such a third party plugin - and the effect of the issue is essentially that a dual (or higher) processor machine - such as AMD Opterons - may render at a lower performance than it's capable of.
Although this issue has been confirmed by many users of the 3ds max software - a fix for this issue has not yet been provided.
A laborious fix exists by manually setting the processor affinity mask for the 3ds max process to include all processors - after 3ds max has finished starting up. As mentioned - this is rather laborious - and also infeasible on network renders.
With the help of a few Splutterfish forum members and betatesters - we (I) have written a solution to this problem by automatically re-setting the affinity after 3ds max starts up. Essentially this is done through a MaxScript which is run after 3ds max starts up - which in turn calls a third party MaxScript extension (by Larry Minton of Avguard Animations) which contains the affinity mask modification capabilities required.