Right way to detect cpu architecture?

Question

I'm attempting to detect the right cpu architecture for installing either a x86 msi or x64 msi file.

If I'm right, for the msi I need the os cpu architecture

I'm not totally sure if my way is right because I can't test it. What do you think?

private static string GetOSArchitecture()
    {
        string arch = System.Environment.GetEnvironmentVariable("PROCESSOR_ARCHITECTURE");
        string archWOW = System.Environment.GetEnvironmentVariable("PROCESSOR_ARCHITEW6432");
        if(archWOW != null && archWOW != "" && archWOW.Contains("64"))
            return "x64";
        if(arch.Contains("86"))
            return "x86";
        if (arch.Contains("64"))
            return "x64";
        return "";
    }

Are you really going to ship an installer without testing it first? That's courageous. — Hans Passant, Jan 07 '10 at 01:04
I can test it but just on one x64 machine and one x32 machine not on every cpu type...that's the problem — Kai, Jan 07 '10 at 01:05

Michael · Answer 1 · 2010-01-07T06:48:45.197

3

You could P/Invoke to GetNativeSystemInfo, which will give the CPU architecture of the OS, even from within a 32-bit process on a 64-bit OS.

edited Jan 07 '10 at 06:48

answered Jan 07 '10 at 01:13

Michael

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And that's what this gives you. – Michael Jan 07 '10 at 01:44
A 32-bit Windows system can be installed on a 64-bit CPU. Both MSDN and your answer "the actual CPU architecture" tell me that GetNativeSystemInfo reports x64, but Kai needs to be told x86 in this case. – Windows programmer Jan 07 '10 at 06:38
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Tweaked answer again. On an x64-capable CPU running 32-bit OS, this function will return that the system has an x86 system. – Michael Jan 07 '10 at 06:49
Next you need to tweak MSDN :-) – Windows programmer Jan 08 '10 at 04:14

score 0 · Answer 2 · answered Jan 07 '10 at 00:49

0

The right way is to call IsWow64Process. This API "Requires Windows XP SP2, Windows Vista, Windows Server 2003 SP1 or Windows Server 2008" though. This method is even easier.

answered Jan 07 '10 at 00:49

stuartd

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That won't tell you what the CPU arch is, only what the process itself is running as. – mletterle Jan 07 '10 at 00:51
Do you need the OS architecture or the actual CPU architecture? – Nathan Osman Jan 07 '10 at 00:54
I need that architecture which is important for running the right msi. the code is part of an updater that downloads the msi and executes it. – Kai Jan 07 '10 at 00:58
...as you might know there's no msi that runs on 32bit and 64bit cpus. due to that I need to choose the right one which i'm providing on the server. – Kai Jan 07 '10 at 00:59
@stuart: the intptr size method seems to be simple but will fail on WinNT. – Kai Jan 07 '10 at 01:06

score 0 · Answer 3 · answered Jan 07 '10 at 00:56

0

Simple, try executing a 64bit application. If it fails you're on a 32bit platform.

Edited to add, based on what you're trying to do, if you make sure your msi runner application is a 32bit app then use Stuart's method.

answered Jan 07 '10 at 00:56

mletterle

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Right way to detect cpu architecture?

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