Topic: i7 920 - fireface800 - windows 7x64 high cpu on 1 core

i7 920 - fireface800 - windows 7x64 just open a any application that use rme driver(wdm or asio)
(CPU core #5 bounces from 0-35-70%)even if parked.

changing to TI 1394 (Legacy) driver fixed it (less cpu usage and,steady)!
but should it be this way?

can anyone confirm?