rRC timings

[Zatoichi]

I have 2 8gb ram kits in my PC (4 x 4)

Both are Corsair Vengence PC3-12800 (cmz8gx3m2a1600c9)

9-9-9-24

I thought those were the only timings that mattered but my system over clock is unstable with the 2nd kit installed.
I was able to get 4.4 out of my i5 3570k with just a multiplier change.

I guess i should add that this tRC thing is only effecting the XMP profile thing.

In the BIOS I manually raised the trc of the lower one to match the higher which helped a bit but its still not rock solid like it used to be.
I've run hwinfo and checked voltage and temps and it all seems ok. It really does seem to be this tRC timing thing.

Is there anything else I can do to stabilise things?

[kalniel]

Running four dimms is always going to be harder than two to overclock. You will likely need to make sure both sets are set to the worse of the two's values, and even then might need to up the command rate and/or increase the voltage of the memory controller.

[Zatoichi]

10 points!
I just re-read my post and somehow you deciphered my issue!
I didn't clearly state I have trc mismatch timing issues
my
tRRD
tWTP
tFAW

are all a bit different as well as tRC.

If I poke them too much my PC wont post unless I let it power down for 30seconds.
At the moment I've dragged the faster tRC to the lower value and i'm "stable"

By stable I mean one bad boot every month or so. BIOS gets in a tizz but I just tell it the settings are fine and it starts up.

trc is 33 on one pair and 41 on the other. Seems quite a large difference