Hi, I have the same laptop and i installed openbsd on it a few days ago, i compared the dmesg of bsd.rd and bsd.sp/bsd.mp and i found a workaround:
At boot prompt (disable the piixpm driver): boot> boot -c UKC> disable piixpm UKC> quit I checked piixpm(4) but i'm not 100% sure what this driver do, anyway with this my laptop does not shutdown anymore. Alex
