I have a strange thing with my board and wonder if is normal or not?

I can easily multi clock my 965 from stock 133bclk...past 4.2GHz with out any problem with multi x32 but when i try higher bclk as 190 it wont boot at all with mult x16.
I did a test....cleared cmos and set every voltage to auto exept Vcore and Vdimm and my max bclk was ~180...is this normal, maybe a bios thing??
I know my 965 handle 210+ bclk on R2E.

Thanks in advance.