[dvlug] 64 vs. 32 bit

[Grant Bowman]

Thanks for those important distinctions, Rick. Any thoughts as to why
the 64 bit transition hasn't completed yet?  For Linux compatibility
with proprietary Adobe Flash has been a problem in the past but to my
knowledge this and other similar 64 bit compatibility issues seem to
be resolved now for end users.

Grant


On Tue, May 3, 2011 at 2:50 PM, Rick Moen <rick at linuxmafia.com> wrote:
> Quoting Grant Bowman (grantbow at ubuntu.com):
>
>> A question came up the other day about 32 vs. 64 bit computers. To
>> check you can either cat /proc/cpuinfo or just try booting a 64 bit
>> image on your eee Intel Atom.
>
> Specifically, /proc/cpuinfo's 'flags' record should include the 'lm'
> field, which stands for 'long mode', which is a kernel signifer for
> either AMD's AMD64 extensions or Intel's EM64T ones.[1]  Support for
> this has been in Linux kernels since the 2.4 series in 2001 (and indeed
> was already supported when AMD64 existed only in simulators).
>
> Here's an example on a dual-core machine:
>
> ~$ cat /proc/cpuinfo | grep ^flags
> flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pebs bts pni monitor ds_cpl est cid cx16 xtpr
> flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pebs bts pni monitor ds_cpl est cid cx16 xtpr
>
>
> A similar question that sometimes arises is whether one's CPU includes
> the necessary hardware instructions to support hardware virtualisation
> (as opposed to paravirtualisation):  VT-x (aka Vanderpool) processor
> instructions on Intel, or AMD-V (aka SVM) instructions on AMD Opteron.
> Full hardware virtualisation lets you run completely unmodified guest
> OSes in the virtual machine.  You can tell by looking at the "flags"
> listing in /proc/cpuinfo:
>
> Intel:  "vmx" flag (requires kernel 2.6.15 or later)
> AMD:    "svm" flag (requires kernel 2.6.16 or later)
>
>
> [1] Quibble:  You don't mean 64 versus 32-bit in the general sense, just
> x86 vs x86_64.  E.g., 'lm' wouldn't be present on a SPARC64.
>
>
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