While I don't think there's a way to make a true apples-to-apples comparison, I was able to dig up this chart:
http://en.wikipedia.org/wiki/Instructio ... per_second
From there, its a matter of looking of the dhrystone mips rating of a given processor and making a comparison.
The MIPS line of processors tend to run about 1.6 D-MIPS per Mhz clock. I remember looking up ratings for other processors but don't have those handy.
*http://www.mips.com/products/processors ... bit-cores/
Again, it's not apples-to-apples since certain architectures lean toward certain types of calculations but it can at least give you a baseline to work with.