Windows XP reports four (4) CPUs when I have two (2)

[Acidis]

I have Asus PC-DL Deluxe board with 2 Xeon CPUs. Windows XP reports four CPUs in the Task Manager's Performance tab. Is this normal? Is it due to hyper-threading?

 

[Phantasm66]

Yes.... In Hyperthreading, you have 2 physical CPUs and 4 Logical ones.

At least, that's the story. AFAIK, you strickly need code that's hyperthreading aware in order for this to be the case. What this means is that the application has to be hyperthreading aware. This is what I have been told, anyway. It would make perfect sense from an OS / C++ code, etc point of view.

In any case, its a far cry from actually have 4 CPUs, or having 2 CPUs that have 2 cores each. Multi-cored CPUs from Intel and AMD is comming soon.

 

[agissi]

Multi-cored cpus would need very efficient cooling I would assume.

 

[Phantasm66]

They would almost certainly have different heatsinks, fans etc. How different is probably debateable.

 

[NoisySilence]

I sincerely hope you're using WinXP ( Pro or Home ) with that CPU. HyperThreading doesn't work very well with non-multi-threaded applications in Win2K.

 

[Acidis]

I am using Win XP Pro.

HyperThreading doesn't work very well with non-multi-threaded applications in Win2K

What are the problems with using OSs that don't support hyper-threading?

 

[Didou]

The way I understood it, when you're using an application that's not multi-threaded, the OS will still try to spread the workload on both CPUs which will result in a loss of performance.

MS added a little "trick" to XP where it would disable one of the logical CPUs so the application would run only one of them. But if you're using WinXP or any recent Linux Distro, you won't have any problems.

 

[Phantasm66]

Originally posted by Didou
The way I understood it, when you're using an application that's not multi-threaded, the OS will still try to spread the workload on both CPUs which will result in a loss of performance.

The way I've always understood it, all you will get in a non-multi-threaded app is that one CPU will get its cycles all consumed, and then the OS will start to tap the other, that's all.

I am ALMOST SURE that for both CPUs to work on the same calculation at once, the code has to be written to support this.

HOWEVER, what you may have been saying is does the OS balance tasks evenly between both CPUs, even although both of them are never working on the same calc at the same time.

This may also be true. I don't know but I want to find out.