hw RNG support?

Hello,

the (4) random man page describes that kern.random.sys.seeded would not be 
seen if the system has a hardware RNG. Now my chipset (i815) is supposed 
to have one, also I have a box with a HIFN 7951, which, according to man 
(4) hifn, also has a RNG, but I'm seeing the mentioned sysctls.
How can I test if my hw rng is used at all? I'd like to disable 
entropy-harvesting on machines with hw rng.

Thanks,

-Harry