I'm running NW65SP6 on the above hardware and have recently started
having severe performance issues. I can't see any problems on the
server console, but users complain that reading files from the server is
extremely slow. Rebooting the server helps for a while.

Reading TID 10089301 led me to believe that the problem might be caused
by processor hyperthreading. When I go into the BIOS configuration,
though, I see no option to disable hyperthreading. Is it now called
something else?