why would you doubt the processor is 128bit? it's CISC, not RISC like a desktop processor (or is it the other way around? i get em confused). in any case, the PS2 has been out for a few years and so have 128 bit CPUs so you're a bit behind the times that's like saying you dont think any airplane is capable of breaking the speed of sound. ok that's probably too extreme of an example. i apologize.
RISC can go through an instruction cycle faster, but need a lot more instructions per program (in a full program anyway) than a CISC processor. The main ideas behind it were more a design philosophy to make simpler processor designs than for real efficiency reasons. And pcs arent CISC cos they need 2 b for legacy apps. When apple made the switch from CISC to RISC design for the mac, it kept about 90% of its legacy code working. Its more cos its how intel and amd etc like 2 design their desktop market chips.
Technically on the outside of the processor we can treat the x86 architecture as a CISC system, but on the inside in newer generations to get more speed it is actually breaking down the macro-operations into micro-ops which are each executed in one CPU cycle. They call this the "EPIC" style architecture, and is essentially a RISC style execution core with a CISC outside wrapper. This allows assemblers to create x86 machine code out of any object code from a programming language compiler and maintain compatibility across the new Pentium 4 line as well as the older CPUs. I believe AMD has a similar but slightly different approach.
Anyway, I'm not an expert but that's what I understood from someone else talking about it...