I am trying to install Ubuntu/Fedora 64 bit versions on my machine and they shout back saying my CPU does not support x86_64 bit architecture and forces me to use i686 versions.

I am currently running Windows 7 64 bit version on my laptop. The processor is : Intel Centrino Core 2 Duo CPU T6500 @ 2.10 GHz

I am hoping this is the right place to ask this question. Why is it that even though I have a 64 bit CPU, I am unable to install Linux 64 bit OS?

  • Pretty strange problem. I'd check the BIOS if there are processor capabilities disabled. – fschmitt Oct 20 '10 at 9:24
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    Are you sure you have a 64 bit installation cd? Most linux distros have different images for 64 bit and 32 bit archatectures. – Falmarri Oct 20 '10 at 18:47
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    Please post output of dmesg | grep CPU once you boot to shell from the install disc. – SleighBoy Nov 3 '10 at 4:59
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    or cat /proc/cpuinfo – xenoterracide Nov 6 '10 at 13:20

Either you do not have a 64 bit CPU, or your computer is not properly reporting/presenting itself to the installation disc.

The output of cat /proc/cpuinfo | grep 'model name' should tell you exactly what CPU you have. If it does indeed say its 64 bit and if there aren't any BIOS weird BIOS options disabled, then I would say you either have a corrupt live CD or you downloaded the wrong version.

Here's the output of my cat /proc/cpuinfo | grep 'model name'

max@max-desktop:/dev> cat /proc/cpuinfo | grep 'model name'
model name      : AMD Athlon(tm) 64 X2 Dual Core Processor 6000+
model name      : AMD Athlon(tm) 64 X2 Dual Core Processor 6000+

You can check the CPU flags directly to see if it's 64-bit.

$ awk 'BEGIN {RS=" "} /^[pl]m$/' < /proc/cpuinfo
  • lm stands for long mode and indicates 64-bit.
  • pm stands for protected mode and indicates 32-bit.
  • You should see one or the other.

The lm flag will be present at least if the processor is 64-bit capable and is enabled in the BIOS, whether you're currently running with 64-bit or 32-bit binaries. You should be able to do this from an i686 Live CD and get the information you need.

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