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).

Thanks for help