Can any CPU be used in a multiprocessor system??

[DivineWrath]

Before I begin, keep in mind that I'm not a computer guru. So don't rip into me for trying to learn more.

First of all, am I correct in saying that only programs that are built to use multiprocessors can benefit from a multiprocessor system? If a program can only use one CPU at a time, then if I was running 5 or 6 programs simultaneously, would each program use either CPU or would they all use the same one?

Secondly, can any CPU be used in a multiprocessor system? Is there a big difference between... let's say, the Athlon XP and the Athlon MP? Or could 2 Pentium 4s be used in a multiprocessor system?
Would there be any benefit to using a multiprocessor system as your desktop vs. a single processor system... if in both cases the CPUs were the same speed?

 

[Poof]

To answer:

1.) It depends on the program... It is preferable that you have multi-threadable applications with multiple CPUs as one task in the app can spend time on one processor and another thread on the other - both working simultaneously. Otherwise...
1a.) The apps will spread across all the CPUs (unless your OS or program will allow you to manually set the "affinity" of the app - fixing it to a certain CPU.
2.) No, only specified processors can be used in SMP mode (as they call it). If you want dual Athlons, you'll need the MP version.... For dual Intel - the Xeon is the most widely known, certain PII & PIIIs, the old PPros, and I believe the later, 478-pin P4s. These have special instructions in their microcode that can deal with task-switching, etc.
3.) Personally, I think duallies at home for general desktop use is more for the geek factor than anything else... If the machine is to be used as a personal server and/or for rendering apps, and/or for certain games that can utilize a dual, then fine...
3a.) In almost all cases, both CPUs need to not only be the same speed but same "stepping" (microcode generation). There were some cases in the past where people were able to hack their motherboards to accept different speed processors though...

[EDIT: You building a dually? I'll take it if you don't want it! ]

 

[AndyHui]

Pentium 4s are not capable of dual processing. You need to purchase a XEON, or go with the older Pentium III.