To set up SMP
  
  Configure the kernel and answer Y to CONFIG_SMP.
  
  If you are using LILO, it is handy to have both SMP and non-SMP
  kernel images on hand. Edit /etc/lilo.conf to create an entry
  for another kernel image called "linux-smp" or something.
  
  The next time you compile the kernel, when running a SMP kernel,
  edit linux/Makefile and change "MAKE=make" to "MAKE=make -jN"
  (where N = number of CPU + 1, or if you have tons of memory/swap
   you can just use "-j" without a number). Feel free to experiment
  with this one.
  
  Of course you should time how long each build takes :-)
  Example:
     make config
     time -v sh -c 'make clean install modules modules_install'
  
  If you are using some Compaq MP compliant machines you will need to set
  the operating system in the BIOS settings to "Unixware" - don't ask me
  why Compaqs don't work otherwise.