need RAM timings help !

sz0ty0l4

Distinguished
Hey all! I'd apperciate a little help!

I have this ram:
http://www.kingston.com/datasheets/KHX18C10_8.pdf
pc components:
i7 4790 3.6ghz
gtx 980 gigabyte stock clock
fsp raider 650
scythe mugen max cooling

with XMP profile disabled i had bad gpu usage drops ( from 98% to 0% so rly bad ones) on 3d applications like games on my gtx 980.
someone adviced me to try enabling an xmp profile because it can happen that this causes the usage dropping and actually it stopped, but i'm still interested to find out which memory timing will give me the best performance and stability for my setup.

as you can see the ram.pdf i have 3 type of XMP profiles.
first one caused terrible performance it was 1600 default.

I enabled the DDR3-1866 10-11-10-30-2n huge performance improvement, 80% of drops disapeard..

the other one is DDR3-1600 9-9-9-27 i tried aswell but didn't notice the change, however i was only looking on msi afterburner in games.

which is the faster, and which will give the better overall stability for gpu and 3d applications??
Thank you for any answers

 
Solution
There's 2 XMP profiles 1 -2, Profile 1 is the best and takes the sticks to spec (1866/10), generally Profile 2 is an enthusiast profile with a tighter CL or CR (1T vs 2T), These drop to 1600/9 (prob due to weaker memory chips. Run them at XMP profile 1 for best performance, might even pick up a bit if you boost DRAM voltage to 1.55

Tradesman1

Legenda in Aeternum
There's 2 XMP profiles 1 -2, Profile 1 is the best and takes the sticks to spec (1866/10), generally Profile 2 is an enthusiast profile with a tighter CL or CR (1T vs 2T), These drop to 1600/9 (prob due to weaker memory chips. Run them at XMP profile 1 for best performance, might even pick up a bit if you boost DRAM voltage to 1.55
 
Solution

sz0ty0l4

Distinguished
Thank you. I'd have 1 more question if you dont mind. I was thinking on getting 8gb more ram. should i go for the same , or it's possible to run 2 rams on different xmp profiles? for example if i pick up a 8gb with higher frequency than 1866mhz?