HP xw4400 Workstation - Manual (Page 8)

On most recent 64-bit Linux distributions (including RHEL 5.4, SLED/SLES 10 SP2, SLED/SLES 11, and
updates to those streams), the kernel automatically detects that NUMA is enabled. Certain older 64-bit
Linux distributions such as RHEL 4.7 require the use of the numa=acpi kernel parameter on the Z600
and Z800 Workstations.
4 Chapter 1 Linux on HP Workstations