Ok, this was a test i wanted to do on my own also. I have an original Digital Audio 466 and an original Sawtooth 450.
The DA 466 is set to 533 and runs fine in a quicksilver.
The ST 450 is set to 550 and Kernal Paniced once the desktop was shown.
The ST 450 is set to 500 (667 in QS) and runs fine in a quicksilver but is a bit sluggish for video playback.
Here are some shots i took while the cpu's were in my system.
*fyi. it says AGP Graphics but indeed the hard drive was a swap from my Sawtooth into my Quicksilver*Original 733 overclocked to 800733 System Profiler450 clocked to 500450 System Profiler466 clocked to 533466 System Profiler
I hope this helps with your cpu Knowledge