Sorry on the other points if I misunderstood.


Perrin Harkins wrote:
>> A 32bit Linux kernel can access memory > 4Gb (I think this mechanism is
>> called PAE and was even a feature of older Pentium 3 CPUs).

>
> I've never seen anyone actually use PAE. It may be because of the
> performance hit, or because it requires compiling your own kernel, in
> an age where that's no longer very common. Even getting 4GB of RAM to
> work in 32-bit Linux was fairly tricky until recently.


Take RHEL4 (which must be almost 3 years old by now) the 32bit SMP
kernel supports > 4Gb RAM out of the box.

$ less /boot/config-2.6.9-5.0.3.ELsmp
# CONFIG_NOHIGHMEM is not set
# CONFIG_HIGHMEM4G is not set
CONFIG_HIGHMEM64G=y
CONFIG_HIGHMEM=y
CONFIG_X86_PAE=y
CONFIG_HIGHPTE=y


Yields on SMP 32bit 8Gb machine:

7295MB HIGHMEM available.
896MB LOWMEM available.
found SMP MP-table at 000f4fd0
On node 0 totalpages: 2097151
DMA zone: 4096 pages, LIFO batch:1
Normal zone: 225280 pages, LIFO batch:31
HighMem zone: 1867775 pages, LIFO batch:31
Memory: 7791552k/8388604k available (2006k kernel code, 71388k reserved,
752k data, 228k init, 6946780k highmem)


YMMV between your choice of distribution. I also notice that the
Uni-Processor build does not have PAE enabled.

Darryl