Doesnt it depend on what your doing, Im considering going for a dual processor system cause I do alot of dvd video re-encoding using Cinema Craft Encoder and from what ive read its suppose to use both processors and give a big performance boost
Dual Cpu's are a benifit depending on what you do with your computer. I do 3D aniamtion and most of my apps are optimized for dual cpu's so I see a major benifit. Unless your doing video, graphics, CAD or running a server I doubt you could justifiy the extra cost. However, I got my last Dual for $2000 CDN so that was only $600 more that the last computer I bought. This one is a dual AMD 1800+ system. There is a lot of heat issues, so get good CPU coolers and a good case with lots of fans if you go dual AMD. Dual Xeon is not really worth the price IMHO. Twice the price for similar performance makes the AMD solutions a better deal.
dealer, to answer your question dual motherboard with CPUs come in Intel & AMD flavors. Usually the AMD route is less expensive. The motherboard is what makes it a 'dual' or 'quad' machine. You just plug the CPUs into the sockets.
I have a dual PIII 1gig (each) on an ABIT VP-6 RAID with XP Professional...........I love it, both processors are used, XP (as 2k) sets the affinity according to load, so both are used as required, and equally. With duals, you have double the CPU cache and double the instruction set. Multitasking is far faster and far more powerfull. This is especially noticable when running disk intensive apps like video encoders. I have yet to slow it down, I can encode, surf, download, watch TV (I have an All-in-Woder Radeon), burn CD's, read and send mail, and play mp3's all at once witjh never any slowdowns...................
If you are gaming, and playing a game that does not use the Quake 3 engine (that is the only gaming engine that is SMP, right?) then when you game, you will only be using one CPU.
However, the load of the OS will equally distributed (most of the time) across both CPUs, therefore, XP uses ~50% of the CPU on a single system or ~25% of each CPU on a dual system.
(Those percentages are presented for illustrative purposes and are not intended to be accurate except when relative to each other)
So, even if the program you choose to use is not SMP, you still might see a benefit in a dual rig. The non-SMP program will not run faster, but you will be able to multi-task much better with a decreased chance of over tasking your CPU.
Besides, Photoshop, Premiere and other programs like that are already SMP enabled.
If you are penny pinching when building a machine, then you should probably opt for a high-end single CPU. But if a few hundred extra (yes, one extra chip and about $100 extra for a dual board) won't break you, then definately consider it.
Also, some people use Durons because some of them are stable in dual rigs and they are cheaper. However, most people just opt for the MP line from AMD.