I was wondering how does a modern ARM chip based on ARM Cortex A8 compare, in clock-for-clock performance and capability, to a modern x86 chip such as a Core 2 Duo or Core i5?

I realise due to the different instruction sets it'll depend heavily on what you're doing.

To put it another way, rendering a web page in webkit on a 1GHz ARM Cortex A8 based chip should be about equivalent to doing in on a Core i5 at __ MHz?

Update October 2013:

Since I asked this question years ago it's become a lot more common, when reading about mobile devices, to see architecture-agnostic benchmarks that you can compare across platforms - for example, in-browser benchmarks like Sunspider in Webkit will run on just about anything and you see these in reviews all the time now. And there's things like Geekbench now.