CPU Test Problem - Overclocled Phenom II northbridge

[RainbowSlayer]

Okay, I did 4 CPU tests after overclocking my Phenom II x4 955 to 3,9Ghz

I did score every of them to around 4450 points.

Then I went and overclocked NorthBridge from 2220mhz to 2442mhz.
I raised the NB voltage from 1.1V to 1,16V.

I ran prime95 large for 30 minutes without issues or 'core stopped working' problems.

Then I ran CPU tests for 4 times again, but this time, I scored only average of 4150. What can be the issue?

When doing Super PI, my time went down half a second, so overclocking was a success there, but not in Perf Test 7.0.

Thanks for any help..

[David (PassMark)]

There are timing interactions between the bus and the CPU clock speeds. You might find there is a sweet spot where you get the best performance, and other settings where it drops off.

There are some graphs here,
http://www.overclockers.com/the-importance-of-northbridge-overclocking-with-the-phenom-ii/
Showing that increasing bus speed doesn't always increase performance.

[RainbowSlayer]

Yeah, I see. But the differences shouldn't be that huge.

And one thing more, why are my scores so low? I have understood that the PII X4 980 is basically the same processor but higher stock clock. And passmark charts say that it gets nearly 5k score, though my max was only 4500 in this... Also, my friend got 5,1k with 4ghz with 955.

EDIT
And, according to your NB overclocking charts, 2400mhz would be the optimal for 3,8ghz. I have 2442Mhz and 3885mhz, so...

[David (PassMark)]

according to your NB overclocking charts

The chart at overclockers.com is not our chart.

And one thing more, why are my scores so low?

The average AMD Phenom II X4 955 scores 3955 for the CPUMark.
You are saying you got 4450 after over clocking. Which doesn't seem so bad.

But if you think it is slow, then this post covers all the common reasons.
Causes and Solutions for a slow PC

[RainbowSlayer]

Okay, well thanks.