Now this is just for information. Yesterday I an into a problem with a new install of Debian, motherboard being a Gigabyte X79-ud5 (this is significant). Debain 7.0 was installed from DVD's then upgraded from the net to 7.1. This worked OK for a number of days then the follwing error came up in the kernel log (it did not appear in dmesg). "kernel BUG at /build/linux-s5x2oE/linux-3.2.46/mm/slab.c:514! invalid opcode: 0000 [#1] SMP CPU 4" This was followed by a register dump and a call trace and another message.. "BUG: unable to handle kernel paging request at fffffffffffffff8" an another register dump and call trace follwed by the message.... "Fixing recursive fault but reboot is needed" Follwed by........ "INFO rcu_sched detected stalls on CPUs/tasks: { 4} (detected by 1, t=15002 jiffies)" This was followed by an NMI backtrace....... After reboot system started giving regular bug reports stating a CPU had hard locked and the system was for all purposes unusable. After anothe reboot I mamaged to get it in a lucid state for enough time to compile my own kernel (3.7.9). System has worked OK since the custom kernel was installed. A glance through the logs showed the debian kernel was having problems with the APIC. The previous version of debian testing obtained around 2 months before the releae of 7.0 would not boot at all on theis motherboard due to APIC problems. It seems the current Debian kernel does not like a Gigabyte GA-X79 ud5 mother board. System is working no problems on the custom kernel. Its probably worth sending Debian a bug on this................... Using linux for 20 years, Lindsay