Bus speeds, quad pumping and all that...

[digikid]

We're buying a new dual machine to be used mainly for scientific calculations, as well as being the server for some 10 odd X-terminals running Linux. We're aiming for a dual P4-2.0 Xeon with 2GB dual channel RDRAM on a FSB400 MB.

My question (and confusion) is concerning the FSB speed: P4 MBs are running at 400MHz, or is it "quad pumped 100MHz"? What exactly does this mean? The RDRAM is running at 800MHz, right? or 8*100MHz, or...? I don't get it. Is the FSB speed the reason why AMD seem to perform better per clock cycle these days? The XPs run at 2*133MHz?

Finally, I understand that the FSB533 is coming sometime soon, May is it? Will this be a huge performance increase in the P4-systems? Is it worth waiting for? I know that our 2 dual PIII-800's, one with a FSB100 and the other with a FSB133 certainly benefit from the faster FSB.

Thanks for your time.

 

[Crashman]

Yes. Intel uses a QDR bus, transferring 4 bits per trace per cycle, instead of one. The main reason the P4 sucks is not its bandwidth (it has much more than the Athlon), but its design. The QDR533 bus is at 133 actual MHz, which helps some also. Right now I think the Athlon would benefit more from the added bandwidth than the P4.

What's the frequency, Kenneth?