I recently upgraded some components of my desktop PC. I was suprised to discover that RAM doesn't work with declared speed of 3000 MHz. Here is the solution I've found to this problem.
Back in the days of DOS I can remember having to set up everything manually, like selecting IRQ number and DMA channel to make sound working in games. But today, in the era of Plug&Play, assembling a computer is easy and everything works automatically. Almost everything...
Although I found that both my new motherboard (Gigabyte GA-Z170-HD3P) and RAM modules (Corsair Vengeance LPX DDR4, 32GB(2x16GB), 3000MHz, CL15 (CMK32GX4M2B3000C15)) support 3000 MHz frequency, it worked on 2133 MHz. Motherboard specification says: "Support for DDR4 3466(O.C.) /3400(O.C.) /3333(O.C.) /3300(O.C.) /3200(O.C.) /3000(O.C.) /2800(O.C.) /2666(O.C.) /2400(O.C.) /2133 MHz memory modules", while specification of the memory has "3000MHz" even in its title. What happened? Motherboard spec calling all the frequencies higher than 2133 "OC" (like in "overclocking") gave me some clue that it is not standard.
After few minutes of searching on Google, I've learn about a thing called XMP (Extreme Memory Profile). It's an extension to SPD (Serial Presence Detect) - a protocol used by RAM modules to report to the motherboard what parameters do they support. I then checked in the specs that my motherboard, as well as my memory support XMP 2.0.
So what I finally did was:
That's all! Fortunately I didn't need to manually set any frequency, timings or voltage of my Skylake processor, memory or any other components, like overclockers do. With all the other settings left to default "Auto", the computer still works stable and RAM now runs with 3000 MHz frequency.
By the way: Please don't be worried when you see only half of this frequency in HWiNFO64 tool as "Memory - Current Memory Clock". All in all we are talking about DDR here, which means "Double Data Rate", so the real frequency is just that, but data is transferred on both rising and falling edge of the clock signal.
Warning! It turned out that enabling XMP on my machine makes it working very unstable. Firefox, The Witcher 3 and basically all memory-intensive applications crashed randomly. So if you experience similar issues, you better disable XMP or, if you know any better solution, please post a comment about it.