3DMark11 - Confusing memory performance

[zaniro]

I have been testing my Sapphire 7950 Vapor-X memory overclock on 3DMark11 and came up with some odd graphic score results:

1.22v:
1200 - 1250 = 10688
1200 - 1275 = 10505
1200 - 1300 = Unstable
1.23v:
1200 - 1300 = 10601
1200 - 1350 = 10676
1200 - 1400 = 10762
1200 - 1450 = 10809
1200 - 1500 = 10880
1200 - 1525 = Light Blue Screen Lock-out

I have only previously overclocked a 7850 and the memory performance increased from 1200 to 1250 (score increased by 84) and anything above resulted in a performance decrease. I tried searching to see if anyone else had a similiar 7950 experience with memory performance but had no luck. Is it normal to see a dip in performance then a increase at higher memory clocks? Should a memory increase of 250MHz result in a score increase of around 192?

 

[manofchalk]

I found the same with my 7870, beyond a certain point pushing the memory clock degrades performance.
Don't know the reason behind it, but just what I observed when I overclocked my card.

 

[zaniro]

I found the same with my 7870, beyond a certain point pushing the memory clock degrades performance.
Don't know the reason behind it, but just what I observed when I overclocked my card.

It is supposed to be an indicator of memory instability. It just puzzles me why performance decreases from the memory clock range of 1251 - 1399 then after 1400 increases until 1500. This indicates memory instability within this range (1251-1399) but I have not come across memory performance decrease followed by performance increase at higher clocks. Maybe this is a sign of malfunctioning hardware - RMA candidate possibly.