[jsn]

The original Calxeda reference design from last year was a 2U rack-mounted chassis that crammed 120 processors (and hence server nodes)

also:

HP can cram three rows of these [4 CPU --jsn] ARM boards, with six per row, for a total of 72 server nodes

From that I conclude that in their calculations 1 CPU == 1 server.

[tmurray]

Each CPU is a separate node in this configuration--separate DRAM, IO, etc.