I personally have never used a dual-proc machine myself, but if it's merely recompiling your kernel that it takes, it shouldn't be too much work. Slackware 10.1 comes with the linux-2.4.29 kernel (at least mine did) so you have two options. Either recompile your current kernel, or download a newer one from www.kernel.org
and recompile that one with SMP support added. I'm going to guess it'd be easier to just recompile the one you have currently, but I'm not 100% of the process as I've only updated mine.
I don't know how familiar you are with Linux, so if anything needs to be explained in greater detail, let me know.
Alright, first things first, mosey on over to /usr/src/linux (this is where the source of your kernel is stored, it's just a symlink btw) and copy the .config file somewhere safe, like ~. Those are the current configurations for your kernel, and while we aren't doing anything hardcore, if something goes wrong, it'd be nice to have a backup lying around. Head over to /usr/src/linux as root and:
This will open up a menu, and it allows you to change the options of the current kernel .config file. Head over to Processor type and features ---> and scroll down. You should see [ ] Symmetric multi-processing support or SMP support. Highlight it and press Y (a little * should appear where there wasn't anything, this means you're going to build it directly into the kernel, rather than as a module, for future reference). Exit out of menuconfig, and be sure to save your configuration (it'll prompt you when you try and exit).
After that you're going to have to run these commands from within /usr/src/linux to build the kernel:
$ make dep
$ make bzImage
(normally you would have to run $ make modules && make modules_install to make/install any modules, but since we only changed the kernel, it isn't necessary. If you added modules as well, you have to do this step too)
$ cp arch/i386/boot/bzImage /boot/vmlinuz-2.4.29-smp (this copies the new kernel into your /boot directory, I added -smp so you could differentiate between the two)
$ cp System.map /boot/System.map-2.4.29-smp
$ ln -sf /boot/System.map-2.4.29-smp /boot/System.map
Huzzah, you just rebuilt your kernel. Exciting.
Now, depending on if you use LILO or GRUB (probably LILO if you're using slack) open up /etc/lilo.conf in your favorite editor, and we need to add a new entry for your new kernel (if something goes wrong, you can always go back to your old one and try again). Keep scrolling down until you see something like
image = /boot/vmlinuz.old
root = /dev/hda6
label = Linux_2.4.29
Or something like that (yours will be different, that's a snippet from mine). Add this to it:
image = /boot/vmlinuz-2.4.29-smp (says which kernel to use)
root = (whatever your / partition is on, mine is /dev/hda6 yours is probably different, check $ df to see which partition / is mounted on)
label = Linux-SMP (so you know which one has SMP support)
Save your additions, and run the command
And after that, reboot and see if you can boot from the new kernel and see if it detects your other proc. To check, do
$ cat /proc/cpuinfo
And both processors should show up.
Here are some links that might help you out, but I think that should do it for you. gl hf