With a look to the Instruction/Data Cache sizes of the CPUs you can get an
idea why the performance units are like that:
The 989KS/100 has an Instruction Cache size of 2048KB and a Data Cache Size
of 2048KB.
The N4000-100-220 has an I-Cache size of 512KB and a D-Cache size of 1024KB.
I do not know how the HP e3000 performance Units are measured but the
N-Class should be faster regarding I/O activities because of higher PCI BUS
Speed in comparision to HP-PB Bus speed.