BClock limitations: IOH V, PLL V? QPI?

[tomb18]

HI,
I was wondering where the limitations for the BClk on the X58 platform come in. On my system I see a maximum of 205 whereas others can get this higher. Is this directly related to the CPU or isd it related to the QPI frequency? If it is related to the QPI frequency then wouldn't increasing the IOH voltage a notch help?
ANy ideas where the limitation comes in? Is it the clock itself?

[FabricioGS]

I wonder the same. My max bclk is 207. Besides QPI voltage (wich I have tried very high), I'd like to know if ICH or NB voltages could help my with that.

[hicookie]

2 possible, cpu side, the other side its IOH
due to the QPI bus on each side limits the Bclk
around 220MHz is IOH bettleneck, i saw some could reach over 230Mhz
but very few, hope new stepping IOH could improve this (QPI Bus 8GT/s)