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Dual core x Dual procesor - What does it mean?

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June 21, 2005 3:37:27 AM

I was reading some explanations about dual processor and dual core and I found myself a little confused about this topic....

I have been a little difficulty to understand what is the real difference between them.
I know that Athlon has your memory controller on die and it has a better performance. But what about the Xeon and P4-D? The only way to increase the perfomance is just through their L2? Look at the simple example below:

Intel Xeon Dual Core: they use just one FSB. Two processor Xeons are conected in only one FSB 800 MHz.

Intel Petium D Dual Core will be share the same FSB 800/1066 Mhz and can use non-buffered and unregistered memory. May I consider it as an advantage under Xeon?

AMD Opteron Dual Processor: they use the HT (Hyper Transport) with high speedy to access the RAM and the chipset. It is an unquestionable fact that can make all the difference.

AMD Athlon 64 Dual Core: they will use the same memory controller. We can have the same performance when they will use the same FSB?

Well, it is confused.... somebody could help me to understand all this complete process?
Thanks
June 21, 2005 4:10:03 AM

Dual Processor - two physical processors are plugged into your motherboard

Dual Core - one physical processor is plugged into your motherboard. But this one physical processor is actually two processors in a single piece of silicon

On Cache and Bandwidth:
You do mean cash, and fan width goes to Intel right? - endyen 05
June 21, 2005 6:59:42 AM

Pentium D == 2xXeon/1Mb in a single package.

There is no difference, other than the fact Pentium D requires only a single socket:

- cache to cache and cpu to cpu communications go over the FSB .
- single 800MT FSB shared by 2 cores (yes, also 2xXeon uses a single FSB)
- single dual channel memory controller

There is no benefit or disadvantage performance wise for one over the other. Not even the (un)registered RAM, since that is a chipset issue, and AFAIK both chips can work with either registered or unregistered RAM.

NOw for Athlon X2 versus 2xOpteron, there are some differences:
-cache2cache and cpu2cpu communication does not go off silicon, it goes over the internal cross bar (which is way faster than over the 'fsb')
- Only one (DC) memory controller for 2 cores. Athlon X2 looses an advantage Opteron has over Xeon (memory bandwith scaling with more cpu's)

In practice, dual core Athlon (or DC opteron) seems to perform generally on par, or even slightly faster than 2x Opteron at same clock, in spite of half the bandwith per core, and because of the significantly faster core2core communication. For some apps 2xopteron should be even faster though.

Look ahead to dual core Xeon, it doesn't look good for Intel compared to dual core opteron. DC Xeon will have dual FSB ('twincastlle'), so maintaining its current Xeon 800MT per 2 cores bandwith, but it will still only have a single memory controller, this time for 4 cores, and it will gain nothing from faster cpu2cpu communication. Opteron gains memory bandwith as you add cpu's (and therefore, memory controllers), and has plenty of bandwith (HT links) to communicate between cpu's, and has the crossbar advantage. If you think this will be ugly for 2 socket DC Xeons versus 2 socket DC Opterons, just think what bloodbath will occur in the (admittedly, small) 4+ socket market.

= The views stated herein are my personal views, and not necessarily the views of my wife. =
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