Turning onoff SMP support without rebooting

The distribution does not matter. The only thing that does matter is the way the kernel was compiled. Turning off all but one of the processors can spoil performance if you actually need more than one processor.

I have two dual-processor machines. One has two hyperthreaded XEON processors, so it runs as though it had nearly four processors. The other has two Pentium-III processors, so that one runs as two.

When I run Windows XP Home on there, XP Home is brain damaged more than usual, so it runs only one processor. Pathetic.

Red hat notices whether your machine has one or more processors during installation. If it detects only one, it installs only the UniProcessor version of the kernel. If it detects more than one, it installs both the UP and SMP kernels, and (new versions) set GRUB to prefer the SMP version one at boot time, though at boot time, you get 10 seconds to request the other kernel. Older versions do the same thing, but use LILO instead of GRUB.

It might be that you can use your BIOS to turn of multiprocessing, but you have to reboot to do that too.

Why do you want to waste a processor?

-- .~. Jean-David Beyer Registered Linux User 85642. V PGP-Key: 9A2FC99A Registered Machine 241939. ^^-^^ 07:05:00 up 104 days, 1:03, 3 users, load average: 4.30, 4.29, 4.19