Problems with BCLK overclocking

Hi there,

here I have a Fatal1ty H170 Performance/Hyper with a Celeron G3900. It's stable with stock settings, but when I change the BCLK to 125 MHz so that the CPU is running with 3.5 GHz, Prime95 28.9 will crash after some minutes with the blend test. Yes, crash - it doesn't shows an error, it simply crashes. The cooling is fine, it is a Thermalright Silver Arrow SB-E.

I tried to change the VCore to 1.3 V which doesn't changes anything. The RAM is left on auto which means it is underclocked to DDR4-2000 (it is really DDR4-2800).
This behaviour is the same with BIOS 1.60 and now 7.20.

What can I do to improve the stability?

Also I noticed that the BIOS shows me a cache frequency of 2750 MHz while AIDA64 shows a north bridge clock of 3500 MHz and a system agent clock of 1000 MHz. I assume that cache frequency in the BIOS is north bridge clock in AIDA64, so why do these two don't match?

wardog wrote: Google search using: overclock vccio vccsa

Thank you for the hint, I added +0.05 and later +0.1 V to these voltages, but the problem hasn't changed at all. I also tried to increase the PLL and PCH voltages this way, but it was pointless as well. What else could I be doing wrong?