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SubjectRe: 10 GB in Opteron machine
On Fri, Jul 22, 2005 at 11:31:38AM +0200, Christoph Pleger wrote:
> Hello,
> > There is no highmem option for the 64-bit kernel, because it doesn't
> > need one.
> I have two questions:
> 1. Is it possible to compile a 64-bit kernel on a 32-bit machine (or at
> least on a 64-bit machine with 32-bit software) and if yes, how can I do
> that?

Yes. On Debian Sarge, I have a few wrapper scripts to accomplish it -
all attached to this mail - just untar them in /usr/local/bin on a
standard x86 32-bit Sarge distro. Use 'kmake' instead of 'make' when
you are working with your kernel source (eg. 'kmake menuconfig', 'kmake

Sarge comes with all the necessary toolchain support to build a 64-bit

It should be equally possible on most other distros of course, I just
haven't felt the urge to go waste my time with them :)

> 2. All other software on the machine is 32-bit software. Will that
> software work with a 64-bit kernel?

Yes. You tell your 64-bit kernel to enable 'IA32 Emulation' (under
Executable file formats / Emulations).

This is really the clever way to run a 64-bit system - 99% of what is
commonly run on most systems only gains overhead from the 64-bit address
space - tools like postfix, cron, syslog, apache, ... will not gain from
being native 64-bit.

The kernel however will gain from being 64-bit - and it will easily run
your existing 32-bit apps.

Solaris has done this for ages - maintaining a mostly 32-bit user space,
a 64-bit kernel, and then allowing for certain memory intensive
applications to run natively 64-bit.

It's a nice way to run a Linux based system too, IMO.


/ jakob

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