A Guide to Dual Core & SMP

[Raj]

Dual-core is a hot subject at this point; this guide is meant to answer the most common questions about dual-core and its close relative, multi-processing. For a more in-depth look at dual cores, HyperThreading and multiprocessing, you can read kram's article on the subject:


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 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?

No. Games 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. So if you’re going to be using a computer mostly for gaming, get a faster single-core chip over a dual-core one.

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.)

Will all motherboards that run single-core ships with the same socket (e.g. LGA775 for Intel or Socket 939 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?

Not yet, but they are in development on both the Intel and AMD sides.

Which manufacturer makes the better dual-core processors?

I hate to stir up an Intel/AMD debate, but the general consensus, based on benchmarks from the hardware-review sites, is that the AMD dual-cores have better performance. However, many of the Intel dual-cores are much cheaper, and the performance difference isn’t that substantial. So choose Intel if you’re on a budget and AMD for cost-is-no-object performance.

[fireshark]

Remember kids, when buying Opterons, the first number is how many procs in the mobo its designed for.

So the 146 and 148 are only 1 processor opterons
250 is a two processor board maximum opteron
I dont know aboutt hr 8xx series