I reply to myself I found a solution in an old bug report: http://www.freebsd.org/cgi/query-pr.cgi?pr=i386/25958 The solution is to disable the MTRR support with this line in /boot/loader.conf: machdep.disable_mtrrs=1 I think that this information should be added in the Handbook or in the FAQs -- http://swpat.ffii.org/ Giuseppe