Disabling APIC on FreeBSD

A friend who is an avid Linux user, and a prolific programmer, specializing in graphics effects, tried installing FreeBSD in what he describes as “a machine conjured from parts found in my closet” :-)

Surprisingly enough, it worked! FreeBSD managed to come up, but then he asked me about disabling APIC on FreeBSD. IIRC, having APIC enabled caused interrupt assignment problems on his laptop, so here’s a step-by-step guide for disabling APIC on FreeBSD:

  • Stop the boot process at the boot-loader prompt, “OK”.
  • At the loader prompt, type:
    set hint.apic.0.disabled="1"
  • Boot in “verbose” mode:
    boot -v

Then, you can save the “/var/run/dmesg.boot” file, and if anything seems odd or out of the ordinary, you will have enough debugging info to post to FreeBSD developers, to troubleshoot any remaining issues further :-)