Dual CPUs

I know that only certain OSs such as Win2K and Linux can use dual CPUs. If I were to have a machine with 2 CPUs and Win2K, would the programs I downloaded from the Net be able to take advantage of the extra CPU, or do the programs themselves have to be encoded to use 2 CPUs?

 

A month ago I researched this same question. I wanted to build a machine for running "Maya ", a graphics design program. I found out the following THREE requirements.
1) OS must be dual processor capable.
2) Mobo must be dual processor capable.
3) Software applications MUST be written to manage dual processor systems.
Getting the first 2 requirements is easy, finding applications you want to run, written for dual processor systems is the challange. I decided (when I upgrade my box) to concentrate on all levels of the puter for speed... hardrive, video card, fast memory along with a fast SINGLE processor mobo. I really wanted the dual processor mobo, just would not work for the applications I wanted to run.

 

I just wanna say that Item 3 in Dennis' list could be misunderstood, either that or Dennis has been misled.

Applications not specifically written for Dual Processors (or Quad Processors for that matter) will work perfectly fine on a multi processor system. However, they will not utilize the second processor, but put their entire workload on one processor, which means you will not get any real increase in speed with these applications.

There are only a handful of applications today that support Dual processors - and most of these are at the extreme end of the price scale.

 

That's sorta what I thought. So maybe it's not worth getting dual CPUs unless you're running a network server or something.

Quad CPUs?!!! Are you in ernest? I've never heard of such a thing in my life!!!!

 

I'm very serious, however, the Quad CPU motherboards seem to be server systems only.

I thought Dell had the Quad CPU option in their Precision 530 Workstations, but upon double checking I saw that it was "only" Dual CPU.

The Windows 2000 DataCenter Server supports up to 32 processors, and Windows 2000 Advanced Server supports 8.

 

I want a PC with 32 CPUs and 10 GB RAM. You'd never have to worry about a crash or running out of resources with a monster like that. Well guess I'll start saving my pennies now and maybe in 20 years...

 

I alwas wanted a dualie, i have it and love it. Intel mobo with P4 2 giggers Zeon's with 1 gig rdram.
I can throw anything at it and it flies......i be happy.

 

When you use dual CPUs, do they both have to be the same speed?

 

Yes and they have to be processors specifically for duals.

Xeon and coppermine are multi processors.

Before P4s came out I had a Tyan board (socket 370) and 2 PIII 933 coppermines. It would rock.


FYI. If you have a PIV with Hyper threading do a Ctrl Alt Del and look at task manager / performance tab. You will see 2 processors

Now go look at a twin Xeon machine. You will see 4

 

Sorry, I forgot I was in an old post when I replied.

 

but all the OS will run on the 2nth cpu so you will have some improvement, more noticeable in nt kernels, and also not optimized progs almost always use more than one unique thread, es. in virtual dub you have the editing thread, the status window and the video preview, and a dual system will span them on 2 cpus.

OS based on nt kernel runs better on dual systems, for this AMD has anticipated their dual core project from 65 to 90 nm cpus

 

Win9x operating systems will run on a dual CPU machine, but the OS won't recognise the second processor and therefore it won't get used.

My understanding is that for programs to get the most out of dual processors they need to be optimised for this environment. However, Dual Processor aware operating systems are inteligent enough use both processors. In a simplistic way this means that if you are running Word, and then open up Mozilla the OS will use one processor to work on Word, the other Mozilla. That's not how it actually works, but it gives you an idea of the way it works.

If memory servers me right - and I am moving out of the shallow end of my ignorance here - the important processes are threads. As I understand it threads are process streams. A simple DOS process will have a single thread. A sophisticated Windows process may have many threads. You cannot split a thread over multiple processors. When a new thread is started the OS will look for the CPU with the least load and pass the thread to that CPU for processing. So if you run a single thread program on a dual cpu system it will run at the same speed as on a single CPU system (it may even run slower as you've added a "which CPU will I use" step to the process). If two single thread programs run on a dual CPU system (with an appropriate OS), one thread will go to one CPU, the other to the second CPU. The two processes will run at the same speeds as the would on a single CPU system, but because they are both being worked on at the same time the overal effect is that the two processes are completed sooner than they would on a single CPU system. If a single program utilises multiple threads it should run faster than on a single CPU system. You also have to remember that there are OS threads being processed along with application threads, which complicates the picture.

Last point: two CPUs does not mean twice as fast. I would think 30% faster is more realistic. Don't forget that there is more to the speed of your PC than the CPU. Other key factors are disk access speeds (often the main bottle neck), RAM access speeds, efficiency of chip set, and video card performance (for graphic intensive applications). As for reliability - you've added more complication to the system which is bad for reliability.

 

The easiest way to make this evaluation for yourself is to use a built in system tool called Perfmon. There is a counter in there under System called Processor Queue length. This counter will measure the number of threads that are READY to run, but are waiting for time on the CPU. If, in your standard operations, you find that your queue length is consistantly/regularly higher than 2, a dual processor can add some performance.

This will not help you for surfing the web faster. It will help you on heavily intensive operations, like rendering complex graphics, disk intensive operations like databases, audio/video editing etc..

The other interesting thing about dual procs is how interrupts are serviced. If you have something that exercises a piece of your hardware (like regular high load networking, massive disk IO, etc) this can have some dramatic improvements in perceived responsiveness.

My work machines where i crank on code are dual procs, because compiling large programs are heavy on the CPU. My home machine for msmoney, web surfing and some video games are single procc'd.

 

They have a program on Tom's hardware for dual CPU machines. It sets afinity for the various running programs. They claim it helps the system run better and smoother. I just sold my dual system, two 700 PIII on a abit VP-6 MB, so i can't test it. maybe some dualie owner can try it and report back to the board for others thinking of taking the dual CPU plunge. I am looking for another dual system, but it will have to wait until after My HTPC is built and working great.

Craig