Clock Skew?

[homefry]

CPU Clock Skew
IOH Clock Skew


What are these 2 options for in the bios?

[sn0man]

They allow you to delay or speed up the clock signals. Some use slight delays (200-300ps) and claim enhanced overclocking ability/stability.

Personally I haven't found a need to touch it or any benefit from it.

[Heavybomber]

CPU Clock Skew helped me with my old CPU, it was unable to do 216 BCLK, + 100 ps did the job. But not much than this. Increasing it further gave me instability. I guess these two work with conjunction, and both values must be matched to achieve something better.

[therager]

Exactly:

You have any clock delays set? Either CPU or IOH skew? Setting those to a 'wrong' value can have that effect. I leave those to the defaults as that seems to be the most stable anyways, these settings come into play when you want to push your BCLK hard, which 200 isn't.

OC Gear :
Spread Spectrum ..................: Disabled
CPU Clock Skew ...................: 100ps Really helps over 4.5ghz
IOH Clock Skew ...................: 0ps

3) CPU and IOH skew of 200-400 ps helps me stabilize at over 220 bclock. Also, it is more stable if I make their skews equal to each other, rather than offset at all. Even with P06 BIOS, I got more stable benching above 4.5 GHZ with the skews at 100 ps.
4) Contrary to the P06 BIOS, the G25 seems to like the Aegis Panel more for OS overclocking than setfsb.

this may help some people
set QPI DRIVE strength 10-25 and the QPI latency to 100.
It will help you to get more FSB.

before you ask no i dont know got this from the engineers so give it a try

have fun
thanks

[Mescalamba]

It helps in higher end of OC. I wouldnt be able to reach 4,6 GHz without playing with this..

Downside is, that as efficiency goes, it slows PC down a bit. At least happened to me, so for SuperPI runs and such, not usable. Though QPI drive strength and mild clock skew (100ps) might help.