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How do I know that my CPU supports 64bit operating systems under Linux?

I am running Debian Squeeze, how can I determine whether my processor is 64 or 32-bit? I'm thinking of downloading a 64-bit OS because it's said to perform better.

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marked as duplicate by Michael Mrozek May 12 '12 at 18:26

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

up vote 12 down vote accepted

Type grep lm /proc/cpuinfo (lm stands for long mode)

Or just try booting with a 64-bit OS: if you do not have 64-bit support, it will say so and not boot.

lm: Long Mode (x86-64: amd64, also known as Intel 64, i.e. 64-bit capable)
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look what happen when i've used this comand – Zignd May 11 '12 at 12:34
The lm flag is there, that means your system supports 64-bit. – Renan May 11 '12 at 12:37
it's not true i tried uname -m and it show me i686 exactly as @cjc said – Zignd May 11 '12 at 12:41
uname -m refers to the architecture of the currently running kernel, if you'rre running a 32-bits kernel it will show i686 even if you CPU supports 64-bit. – Renan May 11 '12 at 12:45
@Zignd uname -m can even show i686 to a process on an x86_64 processor running an x86_64 kernel, if the process (or an ancestor) called setpersonality. – Gilles May 11 '12 at 23:11

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