Overclocking in Maximus x hero

[hirbod2568]

I built my first system.
Mb: Asus Maximus x hero,
CPU:Core i7 8700k,
PSU: EVGA gold 850w
GPU: EVGA 1080 ftw2
MEMORY: Corsair vengeance rgb 3466 ( 2*8)
CPU cooling: corsair h110i
In bios there are three options, Normal, Fast(OC 29%) and Fastest(OC 39%)
I have two questions:
1- should it hit my pc if I put it in fast( OC 29%) always?
2- I can run win 10 without problem with fast mode but I faced blue screen in startup with fastest ( OC 39%). Why?

 

[volkgren]

I wouldn't use the auto-settings for overclocking. Each CPU and system is different and a predetermined overclock/setting won't work for every system.

Do some reading and learn how to manually overclock.

https://www.tomshardware.com/reviews/cpu-overclocking-guide,4593.html
http://www.tomshardware.com/faq/id-2920787/beginner-guide-overclocking-cpu.html

and of course if you have any questions feel free to ask.