GA 990 FXA UD7 Only half of the Ram recogniced by Bios

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Bahiga84

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Oct 16, 2014
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Dear PC Gurus of Toms Hardware,

(please excuse my bad english, it`s not my native tongue)

I`m facing a Ram issue known but unsolved. (at least for me^^)
When booting, the post only shows 8GB of installed 16GB DDR3 Ram (4x4GB Corsair Vengeance)
In Windows Resource manager it shows 12GB installed, 4GB reserved for the system , 8 GB usable. You may have heard or read about similar issues, this is my first post :)
Most people have the problem that their Ram don`t run at full speed, i would just be happy if i could use all 16 GB at 1333MHz...

My System:
CPU: AMD Bulldozer FX 8120 (Corsair Watercooling)
MoBo: Gigabite GA 990FXA UD7
Ram: 4x4GB Bundle Corsair Vengeance 1600MHz (CMZ16GX3M4A1600C9) (Run at 1333MHz)
GraKa: 2x EVGA GTX 480 DirectCu II in SLY (watercooled, separate cooling circle 1)
HD1: Corsair F Force SSD 120GB (Sata3)
HD2: 6x Western Digital Caviar Green 1GB (Raid 10, watercooled, separate cooling circle 2)
DVD/Bluray: some DVD Bluray Rewriter from Light-on (sorry, i don`t remember the model)
Windows 7 Ultimate 64bit
1200 Watt Power supply
Sound and LAN is Onboard
(No Overclocking due to the Ram issue)

Bios settings are all on "automatic".

Bios is flashed with the latest version. (F11b ?)
The Ram are listed as supported on AMD and Gigabite.
I checked every module separately with Memtest 86+, no issues found over multiple checks.
CPU cooler is not too tight due to known issues when screwed really tight.
2 modules work fine, 8GB shown and usable, system is stable.
4 modules won`t be recognized by the Bios, i searched many hours over the past few months with no solution. 12GB seen from Windows, only 8GB usable (while 16GB installed, but stable) Bios post shows only 8GB installed.
Windows Ram remapping is turned of.
Windows SWAP file is on SSD drive

I tried different tweaking tips (Ram Voltage, Timings, etc) found in other forums about this problem. Nothing worked.
I had this problem from the start (with the Asus Crosshair V R.O.G.), changed all the 4 Rams to new ones, and also the Mainboard to the Gigabite which i am using now...
Only thing never changed was the Processor, Harddrives and the Graphic cards.

If anyone who encountered said issue and found a way to make it work with all 4 Ram sticks, i would really appreciate the help!

Thanks in advance for reading my long post and for any help that may come!


 
Solution
rolli59
I found out about my channel issue by removing the stick from the working channel and it did not boot at all. I had only 8GB installed in 2 x 4Gb, windows reported 8GB only 4 GB usable. In your case 1 and 3 works as a single channel no problem but nothing is coming from 2 and 4.
Try booting with only 2 and 4 installed.
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Bahiga84

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Oct 16, 2014
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4,510

Thanks for your answer,
I already fear that this is the problem, but i still hope i have missed a Bios related option which i did not test jet...^^
perhaps someone has an idea?
i`m open to any suggestions to test or check...
If i find the solution i will surely post it for everyone facing this issue.
CPU-Z will be installed this evening and then i probably know more...^^

Thanks :)
 
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Bahiga84

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Oct 16, 2014
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4,510
I did some test this weekend,
If i have 2 Ram bricks in slot 1 and 3 i have 8 GB Ram, if i put them in 1 and 2 i have only 4GB while 2GB are reserved for the system?
Thus if i install all 4 modules i have 8 usable and 4 reserved for the system.
CPUz says (while runing 2 bricks in 1,3) i have 8 installed with single chanel mode...
 
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rolli59

rolli59

Titan
Oct 27, 2007
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130,890
I had this issue with a MSI 990FX board and it turned out being a dead channel on the board, I could test the CPU in another working system to eliminate the memory controller. If I read your post right you have had this issue in two boards so it points to bad channel on the CPU unless you are very unlucky with boards.
 
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Bahiga84

Reputable
Oct 16, 2014
5
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4,510


I don`t think its the Channel or the CPU anymore^^
If i put 2 bricks in the slot Nr DDR_1 and DDR_3 it works fine, but if i put them in Slot DDR3_1 and DDR3_2 it shows only 4GB usable and 2 GB reserved for the system.
The channels are (according to the Manual) 1,3,2,4
in 1,3 it works with 2 bricks, in 1,2 it only shows half of the second brick but it isn`t usable.
if i put them 3,4 it shows again only half of the second brick.
so channel:
1: DDR3 correctly seen and usable
3: seen by Bios, usable
2: not seen by Bios but by windows (only half the capacity) but not usable
4: not seen by Bios but by windows (again only half the capacity) but not usable.
sums up to 12GB (2x4 good, 2x4 only half and not usable)
i really don`t have a clue anymore whats wrong with my stuff.
The exact same thing with 2 different Boards and 3 bundles of each time 4x4GB.

Is there anything in the Bios which could work?

Many Thanks Rolli for helping :)
 
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rolli59

rolli59

Titan
Oct 27, 2007
47,790
283
130,890
I found out about my channel issue by removing the stick from the working channel and it did not boot at all. I had only 8GB installed in 2 x 4Gb, windows reported 8GB only 4 GB usable. In your case 1 and 3 works as a single channel no problem but nothing is coming from 2 and 4.
Try booting with only 2 and 4 installed.
 
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