CPU Usage - Internal Audio vs Firewire Interface on Mac

[catalyst]

I have no idea where I got this idea from, but I always assumed that the CPU utilisation on the internal audio in a Mac would be better, or at least the same as when using a Firewire interface.. not so, on mine at least.

Results of Live 8 Performance Test on iMac Core2Duo 2.8 Ghz at 512 latency:

45% M-Audio Firewire Solo

- vs -

55% Internal Audio

Is this pattern typical ? I only use the Firewire Solo as a DAC/Headphone amp, so I was gonna get rid and upgrade to something like a Lavry DA10 connected to the onboard optical out but i'm having second thoughts now and may go for an Apogee Duet instead.

cheers

[8O]

I had similar strange results, see http://forum.ableton.com/viewtopic.php?f=2&t=102164 - couldn't figure it out, so I just forgot about it...

[catalyst]

Thanks for replying mate, it is truly fecking weird that this would be the case