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
– Hans Passant, Commented Jan 7, 2010 at 1:04
I can test it but just on one x64 machine and one x32 machine not on every cpu type...that's the problem — Kai
– Kai, Commented Jan 7, 2010 at 1:05

Michael · Accepted Answer · 2010-01-07 06:48:45Z

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 7, 2010 at 6:48

answered Jan 7, 2010 at 1:13

Michael

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4 Comments

Michael Over a year ago

And that's what this gives you.

Windows programmer Over a year ago

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.

Michael Over a year ago

Tweaked answer again. On an x64-capable CPU running 32-bit OS, this function will return that the system has an x86 system.

Windows programmer Over a year ago

Next you need to tweak MSDN :-)

stuartd · Accepted Answer · 2010-01-07 00:49:41Z

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 7, 2010 at 0:49

stuartd

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5 Comments

mletterle Over a year ago

That won't tell you what the CPU arch is, only what the process itself is running as.

Nathan Osman Over a year ago

Do you need the OS architecture or the actual CPU architecture?

Kai Over a year ago

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 Over a year ago

...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 Over a year ago

@stuart: the intptr size method seems to be simple but will fail on WinNT.

mletterle · Accepted Answer · 2010-01-07 00:56:44Z

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 7, 2010 at 0:56

mletterle

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