# "CPU you selected does not support x86-64 instruction set"

## dilbot

I'm obviously missing something.

Here's my machine:  3.10.25-gentoo #1 SMP i686 Core2 Quad CPU Q8300 @ 2,50 GHz

I used the latest ISO:   install-x86-minimal-20140128.iso

I used the latest stage3:  stage3-i686-20140128.tar.bz2

Then when I try to compile the kernel, I get the "CPU you selected does not support x86-64 instruction set" error.   This happens after selecting either the x86-64 or Core2 options in processors.

The only thing I can think of is that the original ISO is x86 rather than x86-64, but that shouldn't be a factor after loading the i686 stage3.    And anyways, there doesn't seem to be an x86-64 ISO available.

Any ideas?

[edit]  I can get the kernel to compile if I unclick the new 64-bit-kernel option.   But this doesn't really make any sense to me - the CPU is 64-bit.   Everything else compiles fine.  Eh?

----------

## blu3bird

 *dilbot wrote:*   

> The only thing I can think of is that the original ISO is x86 rather than x86-64, but that shouldn't be a factor after loading the i686 stage3.    And anyways, there doesn't seem to be an x86-64 ISO available.

 

It is. You can't compile a 64 bit kernel with a 32 bit system (well, you can but it's complicated).

Best thing would probably be to reinstall using x86-64 iso and stage3. Note that x86_64 is called amd64, because amd invented it: http://distfiles.gentoo.org/releases/amd64/

----------

## dilbot

"Note that x86_64 is called amd64, because amd invented it"

One of those things you have to know because otherwise it wouldn't make much sense on the face of it.

Thanks blu3bird, I'll give that a try.

[edit]   So I've tried the AMD ISO with the i686 intel stage 3.    same problem.   I guess to get 64-bit on intel, you have to use all of the AMD builds (ISO and stage3)?.   I've run out of time to play with this so I'm just going with 32-bit for now.   Hopefully there will be a clearly named path for intel 64-bit in the future.

----------

## szatox

64 bit kernel can run either 32 or 64 bit apps. 32 kernel can only run 32 bit apps.

The easiest way is to download everything you need already compiled for arch you run (amd64 in your case). I've never used gentoo iso image, maybe you can install from this directly without stage tarball? If no, get stage 3 compiled for amd64.

You can also convert your instal to 64 bit. There is howto in gentoo docs how to do that (https://wiki.gentoo.org/wiki/Changing_the_CHOST_variable seems to be fine), just make sure you build new kernel first, you can do that running  genkernel  with --arch-override option. Reboot with new, 64 bit kernel, and THEN follow howto. Otherwise you might find yourself screwed by 32 bit kernel being not able to run your brand new 64 bit userland.

----------

## John R. Graham

 *szatox wrote:*   

> You can also convert your instal to 64 bit. 

 Alas, this is not true. You must start with 64-bit install media and stages if you want a 64-bit install.

- John

----------

