GA-990fxa-ud3 Rev 4. OS see only 8 Gb RAM

[darkshvein]

Hi. At this moment I have current memory config:
2*4Gb Corsair XMS3
1*4Gb samsung.
 On my previous 970A-DS3 OS see all 12 Gb.
On this board watch only 8Gb . For more precision detail, BIOS  inside menu show all 12 Gb, OS (debian x64) only 8 Gb.

I suppose, problem in dual channel mode or DST mode ganged/unganged, but I cant find settings for disable it. Also I tried clear CMOS setting by reset hardware trigger on the board. Cleared successfully, but again 8 Gb.

Please, suggest anything and sorry for my eglish. Thanks.

[Tiger]

If you like mixing different memory kits, then you must like doing your own compatibility testing. Compatibility isn't guaranteed when mixing kits since your combination has never been tested together by the memory manufacturer.

[darkshvein]

more idea's?

[JGB123]

Exactly which DIMMs do you have?

Corsair XMS Memory — Corsair XMS DDR3 Memory kits and PC memory upgrades are mainstream DRAM solutions that allow users to experience outstanding PC memory performance and stability
http://www.corsair.com/en-ca/memory/xms?memorytype=DDR3|

Computing DRAM Overview | Samsung Semiconductor Global Website
http://www.samsung.com/global/business/semiconductor/product/computing-dram/overview