Not having CPU information on Forum Nokia device specification pages has been a source of complaints... well, at least source of frequent queries from developers. This situation is getting corrected as of this writing. S60 3rd Edition Feature Pack 1 devices (like N95 and 6290) already have this information.  Look for the CPU section on the left-hand side column.

Other device specification pages will get this information added during the coming weeks. I hope you will find this information useful.

Of course, there are some non-Nokia sources for the CPU information, like for example this one.