Re: 32-bit vs AMD64 on Opteron for LAMP server
On 07/07/07 07:36:26PM -0400, Roberto C. Sánchez wrote:
> On Sat, Jul 07, 2007 at 05:39:54PM -0400, Jim Crilly wrote:
> > On 07/07/07 04:45:57PM -0400, Roberto C. Sánchez wrote:
> > > >
> > > The stock Debian kernels are configured like this:
> > >
> > > CONFIG_HIGHMEM4G=y
> > > # CONFIG_HIGHMEM64G is not set
> > > CONFIG_HIGHMEM=y
> > >
> > > So, if you have a machine with 4-64 GB RAM, then a custom kernel is in
> > > order. Of course, as far as the BIOS goes, if the machine supports more
> > > than 4 GB RAM, then the BIOS should as well. After all, why would
> > > someone manufacture a machine that can handle more than 4 GB RAM and
> > > then put in a BIOS that cannot?
> > >
> >
> > No, even with just 4G you need CONFIG_HIGHMEM64G because to access the
> > memory from ~3.5G-4G you need to remap it above the 4G mark since those
> > addresses were "stolen" by the various hardware components in your system
> > so you need a kernel able to address >4G.
> >
> Please read again my first sentence. You and I are in agreement on
> this, just saying it in different ways.
>
Whoops, yea I did misread that. But a custom kernel shouldn't be necessary
because on 32-bit systems the 686-bigmem kernel has CONFIG_HIGHMEM64G and
on 64-bit systems there's nothing special needed.
> Regards,
>
> -Roberto
>
Jim.
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