On Thursday 09 September 2004 20:42, Karl Hegbloom wrote: > On Thu, 2004-09-09 at 11:25 +0200, Frederik Schueler wrote: > > This indeed changes quiet a few things. > > Yes, but the 1.8 GHz Opteron is apparently still faster than the 2.8 GHz > Nocona. Rather than a 'my cpu is faster than yours' "pissing contest", > I'd like to see a WHY one cpu is faster than the other discussion. > > It must be mainly due to the thing about how the Nocona isn't really > fully 64 bits wide all the way through the chip... IIRC...? Is that > correct? What other factors are there in this sort of comparison? (I'm > a sophmore CS student.)
- Pipeline length (amd is shorter) - Number of parallel execution units (amd generally has more, I think) - Memory latency (amd has lower latency) - Memory bandwidth - Cache size and structure and latency - Which operations are provided natively, ie. how different x86 instructions are broken down into micro-ops. - How good gcc is at optimizing for that CPU. - System topology. Intel uses a shared Front-Side Bus with memory and IO hubs. AMD uses point-point HyperTransport links and on-cpu memory controller. I'm sure there are others. Which factors are important depend on the code being run. Paul
