8GB but just 3.93GB usable

I have that same memory kit. I was able to get 2667 using the stock xmp profile and setting the dram speed to 2666 in the UEFI.

maffle wrote:

Hello,

thanks for helping. I have actually a bunch of questions now, I hope you can help me out resolving them.

At first, the two rams are the kit called "8GB Corsair Vengeance LPX schwarz DDR4-3000 DIMM CL15 Dual Kit"

Corsair

EAN 0843591069663

SKU CMK8GX4M2B3000C15

I am sure those should be compatibly? If not, may you please forward this to Asrock. They totally werent cheap ones.

I'm sorry but this is hard to explain.

Memory compatibility with the Ryzen memory controller is the worst issue it has. Your memory was designed to work with Intel systems:

http://www.corsair.com/en-us/vengeance-lpx-8gb-2x4gb-ddr4-dram-3000mhz-c15-memory-kit-black-cmk8gx4m2b3000c15

Memory compatibility with Ryzen is mainly luck if it works or not. It depends on the memory chips used in the modules. The memory might work at a lower speed like 2133, but won't work at higher speeds, like 3000. That is what happens with this memory, right? Your memory seems to be only partially compatible with Ryzen.

The new BIOS update which has updates from AMD for memory support does not make any DDR4 memory compatible with Ryzen. It improves the performance of memory that is compatible with Ryzen, but it can also make other memory less compatible. AMD is still fixing the memory support of Ryzen. All DDR4 memory cannot be made compatible with Ryzen. AMD's memory controller design determines if the memory is compatible or not, not the mother board or BIOS. The BIOS can help with memory compatibility, but it cannot ignore what the memory controller requires.

maffle wrote:

The problem is, the AMD boxed cooler is blocking slot 1 of the board, so I put them in 2+4. I am totally sure, Windows showed 8GB usable of 8, when i installed everything. After I made the bios update to newest 3.00, the problem started to happen, only 3.93GB usable anymore.

Your memory should be in slots 2 and 4, that is the best location. I understand what your problem is.

maffle wrote:

First question: Why is it single channel, if the RAMs are in slot 2+4? This seems like a bug of the board / bios.

How important is dual channel mode for Ryzen CPUs? I know form the past, it is really important for Intel CPUs, and makes a lot of performance improvements, but is it that important too for Ryzen?

If I leave the RAMs in slot 3+4, would that be a bad idea? Otherwise it wont work any I dont really know why, and when I put them back in 2+4, Windows showing just the 3.93GB of 8GB.

I cannot tell you why one memory channel is not fully recognized, but I know that is a common problem when memory is not completely compatible with the memory controller. That happens on Intel systems too. It is a very common thing to happen when the memory is not completely compatible, or is set to run at a speed that is too high.

Dual channel memory is always better than single channel memory.

maffle wrote:

I also used reset bios settings (load default). So you say the board chose wrong RAM settings? How?

I actually tried to load the MXP 2.0 profile, but afterwards, the PC didnt boot anymore. The monitor went black for at least a minute, until coming back (I guess the board reset bios to default after this), and when I checked with CPUz, the clocks were still at 1064MHz instead of the 1400MHz what the XMP profile said should be.

I dont really know what you meant with "Did you also notice that the JEDEC timings for 2133 have a tRC of 50, yet tRC is set to 51 in the UEFI?", because I did not share an UEFI picture with those settings. The settings which CPUz showed where the default values the Bios choose, because the XMP profile resulted in black screen / no boot. This is actually another issue I would want to have resolved.

The XMP profile does not work because your memory was designed for Intel systems, not Ryzen. The timings were designed for Intel systems. That is not an issue that can be resolved.

Don't worry about the memory timings I mentioned earlier, you have more basic problems than that.

I agree with wardog, that you should insert the memory in the slots again, and be sure they are inserted all the way and correctly. You should also increase the memory voltage, and just use Auto values for the timings.

If your memory worked better with the other BIOS version, then use the older BIOS version.