I don't think any CPUs depend on data crossing them in a clock cycle, though? The reason to clock lower is so you can do powerful arithmetic in a cycle or two.

I don't think any CPUs depend on data crossing them in a clock cycle, though? The reason to clock lower is so you can do powerful arithmetic in a cycle or two. If you have to build math units out of 4LUTs or 6LUTs your latency is going to suck and your space efficiency won't be very good either.