According to MBM 5.2.0.0 (patched), the 5V line on my BP6 oscillates between 4.22 and 5.16V, while the system is running stable at full load. I get the same readouts when I clock my Celerons to 366 instead of 523 with both CPUs running idle.
Though I only have a standard 250W PSU (about 14A on 3,3V and 20 on 5V), I can´t believe these readouts. 11,37 to 12,89 and 2,93 to 3,33 are the values for the 12 and 3,3V lines.
Is it possible that these values are correct? In that case, I might better get a new PSU