DDR4 memory slow on linux

[compilatus]

Since years i use to test memory bandwidth on linux with 'hdparm -tT' command
or with memtest86+ from boot loader (lilo, grub). On my new machine
(Intel Core i7-5820K, Asus X99-S, Crucial 4x4Gb DDR4 2133) i get surprisingly
low values of 12-13Gb/s for quad channel configuration.
On my previous computer, 4.5 Years old Core 980X with tripple channel DDR3, measured value are comparable (11Gb/s)
My colleague with recent Haswell CPU and dual channel DDR3 got 16-17Gb/s (both hdparm and memtest86)
Also values do not change if i insert only 1 or 2 memory pieces (instead of 4), as if quad channel mode would not work.
Meanwhile i tried other mainboard (Asrock X99-WS) with same results. (BIOS of Asrock board claims quadruple channel mode)
All tests on openSuSE 13.1 32bit and 13.2 64bit with kernels 3.16.2 and 3.17.2

In contrast, on Windows 8 64bit, SiSoft Sandra's memory bandwidth benchmark delivers expected 42-43Gb/s
(CPU-Z shows quad channel memory operation).

Thank for help

[compilatus]

Since this problem is not solved yet,
could someone post his result of 'hdparm -tT /dev/sda' command on his linux DDR4 quad channel machine?
Thanks.

[Michael]

Have you tried like phoronix-test-suite benchmark ramspeed stream

?

[compilatus]

.. to check for plausible results? You are right, i try this, thanks.

[compilatus]

My results of 'stream' and 'ramspeed' tests doesn't look so bad:

http://openbenchmarking.org/result/1506073-BE-DDR4MEMOR85

http://openbenchmarking.org/result/1506079-BE-DDR4RAMSP48

Thanks again.