Core 2 Duo perhaps not recognized as x86_64?

Asked by David Kaplan

Hi,

I installed Edgy Eft on my new laptop that has a Core 2 Duo T7200 CPU. Correct me if I am wrong, but the Core 2 Duo are x86_64 I think. But when I do uname -a, I get:

Linux jaiba 2.6.17-11-generic #2 SMP Thu Feb 1 19:52:28 UTC 2007 i686 GNU/Linux

This looks to me like it is not recognizing the processor as x86_64 despite the fact that I am using the generic kernel. Is this correct? Am I misunderstanding something? In /proc/cpuinfo, I see that both processors are recognized, but there is nothing obvious that indicates 64 bit capabilities.

When I originally installed, I believe I selected the generic desktop ISO, but I thought that changing to the generic kernel would allow me to get the x86_64 stuff out of my CPU. Perhaps I need to reinstall using the 64Bit version of the ubuntu ISO?

Thanks for the help.

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Best lol (azdruid-deactivatedaccount) said :
#1

The Core 2 Duo processor does indeed support EM64T (Intel's implementation of AMD64). One of the nifty things about x86-64 chips is that they can also be used in 32-bit mode (i686), transparent to the operating system. When you installed Ubuntu, you probably downloaded the Standard ISO, which is built for 32-bit.

You can check in /proc/cpuinfo, even; in the bit where it says capabilities, look for "lm", which means Long Mode (AMD64). This doesn't necessarily mean that the processor is running in Long Mode, just that it supports it.

Unfortunately, you <i>will</i> need to reinstall Ubuntu using a 64-bit ISO, as currently, to the best of my knowledge, you can't arbitrarily switch architectures like that.

Good luck in your future endeavours.
Andrew

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David Kaplan (dmkaplan) said :
#2

Thanks Andrew - this makes things much clearer. /proc/cpuinfo does indeed show lm (too bad they didn't pick a more obvious name).

One more question - is there any downside to installing 64bit? For example, are there programs or devices that won't work? I also use ndiswrapper to drive my wireless card and have heard that 64-bit occasionally has problems with that. Should I worry? Is there any way other than having a completely separate Ubuntu 64 install (i.e., dual boot 32 and 64) to have a fallback if things stop working?

Thanks again.

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Bruce Cowan (bruce89-deactivatedaccount) said :
#3

Most things work on the AMD64 version apart from the absence of a Java Mozilla plugin and no Adobe Flash (Gnash is your only option). Another downside is that most 3rd party packages are only made for i386.

Device-wise, it should be the same.

You can install a minimal 32 bit installation within a 64 bit one, but I don't think it's worth it.

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David Kaplan (dmkaplan) said :
#4

Thanks Andrew Wilchak, that solved my question.

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William Bailhache (wobwill) said :
#5

Hi,

I am new to Ubuntu. I have not yet installed it. I have an Intel core 2 system. Which ISO should I install? I am planning to do a duel install of windows and Ubuntu at first then if all goes well maybe transfer over completely.

Will

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David Kaplan (dmkaplan) said :
#6

Hi,

You can either install the standard x86 Ubuntu (32 bit) or the 64 bit version. If you install the standard x86 version, then you will probably want to install linux-image-generic afterwards so you can make use of both processors.

If you install the 64 bit version, I imagine that it comes with a kernel that already supports multiple processors. Have a look at /proc/cpuinfo to check. Note that if you install this version, then there might be some limitations mentioned by Bruce Cowan above.

David

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Lenry (lancecharles) said :
#7

I have an I-Mac with an intel Core2duo 2.4ghz processor. However, when I attempt to run the 64 bit version of Ubuntu that I downloaded on 9/5/2008, it says I don't have a 64bit processor.

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marcobra (Marco Braida) (marcobra) said :
#8

@lenry
Please don't append a new question on a marked as solved question.
Please make new question from here: https://answers.launchpad.net/ubuntu/+addquestion
you will get better chance to get right answer on a fresh tagged "open" question.
Solved question are usually not read from answering people.

Thank you