[Beowulf] "dual" Quad solution from Tyan

[Mark Hahn]

> See page 2 of ftp://ftp.tyan.com/datasheets/d_s4881_104.pdf

sorry for not rtfm!  I wonder if these express links make 
a measurable difference.  or, conversely, on a machine like
this whether people have noticed a benefit to setting IRQ 
affinity under linux.  it's rather easy to notice benefits
of using numactl, even on a dual, so it's probably rather 
important on a 5-hop fabric like this...