So I just upgraded from 2x4GB of RAM to 4x4GB by adding in another 2 sticks of the same type, which is Corsair Vengeance DDR3 1600MHz CL9 (CMZ8GX3M2A1600C9). I was kind of aware that they might not work well together, but I went ahead and did the purchase anyway, because this way there's no need to bother with selling my the original kit after buying a proper 4x4 one.
Turned out my "old" kit is ver8.22, the "new" one (it was a used item) is ver8.16, so there *is* a difference between them afterall.
The first try quickly ended in a fail, since the computer couldn't boot and the monitor didn't get any signal, but after a few hours of DIMM slot changing, Memtest86 and BIOS settings tinkering I managed to get the two kits work together with the original timings. The method that finally worked was disabling the X.M.P and manually setting the multiplier to x16 to reach 1600MHz, and setting the timings to the advertised 9-9-9-24 (from auto, where they appeared the same, yet the BIOS showed 9-11-11-29 in the info segment).
At this point my system seems to function perfectly fine, so only curiosity is driving me to ask the following questions. Here they go:
In CPU-Z the two kits have different X.M.P SPD extensions, different tRC values (that should be the sum of tRAS and tRP, which are the same on each kit). Can I match these values somehow? Is there a point in matching them? The memory tab says I'm in dual channel mode, can/should I set it to quad channel? Can I try to overclock the memory speed and/or the timings and if so, should I go for 1866MHz with the same CL or lower CL with 1600MHz? What programs to use, other than Memtest86 and CPU-Z, to test and check the memory for further details? Is there any point in overclocking my memory if I only use the computer for gaming, browsing, multimedia and occasionally some video-recording? What are the estimated rough percentage gains?
My specs are
Gigabyte Z97X Gaming 3 (the BIOS allows me to change ridiculous a amount of memory timing details, only touched the main 4 as of yet)
i7-4770 3.4-3.9GHz (yes, the non-K version, unfortunately it wasn't me who did the shopping back then)
Corsair Vengeance DDR3 2x(2x4)GB 1600MHz CL9 (CMZ8GX3M2A1600C9)
XFX 550W 80+ Gold
Asus GeForce GTX 1060 3GB
I'll include some pictures of the BIOS, CPU-Z, and Memtest stats, feel free to ask for more if I left something out.
Any and all input is appreciated!