Why is my 8GB 2666mhz DDR3 slower than my old 16GB 1333mhz ram?

[user_friendly]

Question in the topic.

16GB 1333mhz ram: Benchmarked Metro Last Light avg 37.7777 FPS with every setting on ultra(turned off SSAA)

8GB 2666mhz ram: Benchmarked Metro Last Light avg 33.3333 FPS with every setting on ultra(turned off SSAA)

16GB CAS of 9, Team Vulcan mixed with G.Skill

8GB CAS of 11, Gskill trident X only

Running
Windows 7 Ultimate X64
i7 3770k @ 4.4
MSI gd65 MOBO
EVGA SC 660ti

CAS timings are a little different granted. But 8% decrease in frames? Im tempted to buy more ram to match the 16GB.

I might do some tests with the other ram first to see if it truly is CAS timings or if its the 16 GB

ran memtest multiple times everything ok with all sticks of ram

 

[X79]

Did you remember to actually set the 2666Mhz RAM to 2666 in the BIOS?

 

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Yes XMP enabled and tried also disabled for some reason.

Yes all diff ram speeds show up correctly.

I have 3 different sets of mem that i benchmarked all seperately and also on different games, specifically Starcraft HoTS, Tomb Raider, and Metro LL.

Im not sure how i achieved that 37.7 frame avg, i haven't been able to do it again with any ram-set or config. Im marking it off as a fluke.

I admit when im wrong; HOWEVER, i found interesting results in testing the difference between 1600 and 2666 and 2800(OC).

To recap i have 4 sticks 1600(total 16GB) and 2 sticks of 2666(total 8GB)

I tested only with 2 sticks(8GB) of 1600 and found NOT 1 FRAME DIFFERENCE between any other ram i own and tried.

That's right when i OC;d my 8GB 2666 to 2800 and compared the results to that of 1600(both 8GB and 16GB) I found no avg framerate difference. So this test also concluded that 16GB is still not really needed for gaming these days.

I dont know why but i feel like sticking with the 2800 anyways, at least i have about 21 days to make a decision.

I can only hope my mistrials help someone.