The interrrupt 47 shows (with powertop) a curious "Description" :

[@^EM-W] <interrupt>

under a stable Gentoo Linux at a Thinkpad T400  - the BIOS is the latest 
available. FWIW I attached the output of the command  $>cat /proc/interrupts

-- 
MfG/Sincerely
Toralf Förster
pgp finger print: 7B1A 07F4 EC82 0F90 D4C2 8936 872A E508 7DB6 9DA3