How do I tell if the machine my program is running on uses hyperthreading? (C#)

Question

I have some code that needs to know how many actual cores are available on my particular machine, and whether or not Hyperthreading is enabled.

Is there a way to do this in C#?

Update: The machines are a mix of XP and Vista

Update: Accessing 'Win32_Processor.NumberOfCores' or 'Win32_Processor.NumberOfLogicalProcessors' throws an exception (a ManagmentException with the message "Not Found") on one of the machines (but not all of them)

Andrew Grant · Accepted Answer · 2009-02-12T20:30:41.237

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On Vista and higher you can use GetLogicalProcessorInformation via PInvoke to get the number of logical processor units.

On Windows XP there's no way via C# to reliably differentiate hyper-threading from other multi-processor/core configurations. The WMI solution that someone posted will class multi-core processors as hyper-threaded.

Prior to Vista the only reliable means is to check the CPUID of the processor. To use this you could create a native DLL that can be called from your managed code. The following Intel code sample would be a good starting point.

edited Feb 12 '09 at 20:30

answered Feb 12 '09 at 20:22

Andrew Grant

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The link appears to be broken – Anton Feb 12 '09 at 20:29
I thought HT would be 2 logical processor, 1 physical and a dual core would show 2 logical and 2 physical processors. – Szymon Rozga Feb 12 '09 at 20:32

Noldorin · Answer 2 · 2009-02-12T20:34:39.493

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Simple answer to the first question at least: Environment.ProcessorCount should return the number of cores on the machine.

Edit: Here's a non-WMI-based method of checking for whether Hyperthreading is enabled (not that it's any nicer necessarily). Also see this article.

edited Feb 12 '09 at 20:34

answered Feb 12 '09 at 20:20

Noldorin

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score 1 · Answer 3 · answered Feb 12 '09 at 20:18

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System.Environment.ProcessorCount will tell you how many cores exist on the machine the code is running on.

answered Feb 12 '09 at 20:18

GWLlosa

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score 1 · Answer 4 · answered Feb 12 '09 at 20:19

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Check the Environment.ProcessorCount property, it will return an integer, as far as HyperThreading, I'm not sure.

answered Feb 12 '09 at 20:19

Steven DeWitt

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score 0 · Answer 5 · edited May 23 '17 at 12:01

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StackOverflow question 188503 has the information you need ...

Quoting the top answer on that question:

System.Environment.ProcessorCount

returns the number of logical processors (see MSDN)

To distinguish between Hyperthreaded and separate cores, sounds as though you need a bit of WMI.

edited May 23 '17 at 12:01

Community

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answered Feb 12 '09 at 20:24

Bevan

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score 0 · Answer 6 · answered Feb 12 '09 at 20:49

GetLogicalProcessorInformation is sufficient for the HT aspect but sadly it is only available in XP SP3, 64bit XP/Vista/Server 2003 (and I believe is is slightly broken pre vista)

Joe Duffy wrapped this in c# but has not yet released the source, though Mark Russinovich has released the tool (Coreinfo) he created with it, likely you can decompile that to see the code.

How do I tell if the machine my program is running on uses hyperthreading? (C#)

6 Answers6