A Guide to Dual-Core and SMP(from http://www.pcmech.com/forum)

posted in 2006,so something may be out of date.Copied here as a backup.

What is Symmetric Multi-Processing (SMP)?
SMP allows you to run two or more identical processors on one motherboard. An SMP motherboard will have two, four, eight, or sometimes even more slots or sockets. It’s very popular for high-end workstations and for servers. The AMD Opteron uses an alternative to SMP, called NUMA (see Kram's comment later in the thread).
What are some problems with SMP?
First of all, you need a special motherboard with two or more sockets on it. These are often quite expensive, and most of the time they are not standard ATX form-factor, so you need a special case, too. Also, you can’t use standard Pentium 4s or Athlon 64s. On the Intel side, you have to buy Xeon processors, and on the AMD side, you have to buy Opterons. These sometimes also impose memory requirements and the like (i.e. you have to use registered RAM). So in other words, if you want to go SMP, it’s gonna cost you.
What is dual-core?
Dual-core puts two processor cores (essentially, two entire Pentium 4s or Athlon 64s) on one chip package. So you can put in one chip and have most of the benefits of SMP. The Intel Pentium D and Core Duo/Core 2 Duo and the AMD Athlon 64 x2 series are all dual-core.
What are some benefits of dual-core over SMP?
Besides the fact that dual-core costs a lot less (you can use standard motherboards and RAM), the cores are usually tied together more closely. AMD dual-cores use a special dedicated HyperTransport link to tie the cores together; the Intel Core Duo laptop chips are even more closely linked, even sharing an L2 cache. This closer integration means better performance.

Do dual-core and SMP double the speed?
No. If you have two 2.4 GHz cores or processors, you do not have a 4.8 GHz computer. You have a computer that can process two threads at a time at 2.4 GHz each. This will benefit applications (such as Adobe Photoshop and Premiere) that are multithreaded, and it will allow you to run two processor intensive programs at once without lag. That leads me to the next point…
Will dual-core or SMP chips make my games run faster?
Not at the moment. Games right now are single-threaded, so they’ll only use one of the cores. However, if you are, for example, gaming and ripping MP3s at the same time, it will mean your game won’t lag. Also, games will start to take advantage of dual-core, so dual-core is probably the way to go if you are building for the future.
Can you have dual-core and SMP at the same time?
Yes! There are dual-core Xeons and Opterons available, so you can pop two dual-core Opterons or Xeons into an appropriate motherboard and have four cores of processing power goodness. (Needless to say, this is expensive.) The Apple Mac Pro actually has two dual-core Xeons.
Will all motherboards that run single-core ships with the same socket (e.g. LGA775 for Intel or Socket 939 or AM2 for AMD) run dual-core chips?
No. Check on the particular motherboard model’s support site for compatibility. Intel dual-cores in particular require 945 series or above chipsets.
If I want to run a quad-processor system, can I use any Xeon or Opteron?
No! Xeons come in two varieties – Xeon DP (dual processor) and Xeon MP (multi-processor, as in four or eight processors). Likewise, Opterons come in four varieties – Opteron 1xx, 2xx, and 8xx (where xx are two more numbers). The first number indicates the number of that type of processor that can be run in the same motherboard, so you’d need the 2xx series (and not the 1xx series) for a dual-processor system, and the 8xx series for a 4 or 8-processor system.
If I can run four processors in a motherboard, are there any four-core chips?
Yes, but they are extremely expensive and run very hot. Both AMD and Intel are putting two dual-core processor dies on one chip and connecting them via their respective bus standards.
Which manufacturer makes the better dual-core processors?
At this point, Core 2 Duo is the performance leader, but if you are on a budget the AMD chips and Intel Pentium D are still very fast and likely won't disappoint.

 

PS:It seems that Intel has just switched to NUMA in 2009,while AMD has already develop NUMA since 2006 or even earlier.