No POST with 16GB of RAM, only 8GB

[MarkusL90]

Hello everyone! To start off, here are my specs:

AMD FX-8120
Asrock 990FX Extreme3 (brand new)
Kingston HyperX 2x4GB DDR3 1866MHz (and a second, exact same kit)
ASUS Stryx R9 380 OC
XFX Pro 750W PSU
SanDisk Ultra II 240GB SSD
WD HDD 400GB

I recently got a new motherboard (Extreme3) to replace my dead Gigabyte GA-990XA-UD3. Here's what happens. Everything works perfectly with 8GB of RAM (only one 2x4GB kit) but when I stick in the second, exactly the same kit, I get no POST. I also get no POST if I put one stick in 1st and another one in the 2nd slot, if I put one stick in 1st and 3rd slot, everything works just fine and BIOS reports 1866MHz as it should. If I try with 3 sticks, no POST. If I put a stick in the 2nd and 4th slot, things work just fine. I also tried with my old 4x2GB Corsair 1600MHz. I put 4 sticks in all 4 slots and things work fine, except BIOS is reporting my RAM is at 1333MHz instead of 1600MHz.

Tried flashing BIOS, no joy. Tested each slot and each stick of RAM separately and everything is perfectly fine (lot of restarting...). Also, note that these 2 kits worked perfectly fine on my old motherboard.

I'm guessing this has something to do with voltages, but since I've never done any overclocking, I have no clue what I'm supposed to do. NB voltage is 1.145V and DRAM voltage is at 1.585V.

Thank you for reading.

 

[BadAsAl]

I've been trying to help a user with a similar problem here: http://www.tomshardware.co.uk/answers/id-3242358/boot-adding-ram.html#xtor=EPR-8809

My running theory is that the FX doesn't support 1866Mhz in all 4 slots but the computer is still trying to do that. I have suggested that the user manually set all RAM slots to lower frequency and then installing all 4 DIMMS again and seeing if it boots. You should have preset timings in your BIOS for the RAM and can set it to a lower speed profile for each slot.

 

[MarkusL90]

I've been trying to help a user with a similar problem here: http://www.tomshardware.co.uk/answers/id-3242358/boot-adding-ram.html#xtor=EPR-8809

My running theory is that the FX doesn't support 1866Mhz in all 4 slots but the computer is still trying to do that. I have suggested that the user manually set all RAM slots to lower frequency and then installing all 4 DIMMS again and seeing if it boots. You should have preset timings in your BIOS for the RAM and can set it to a lower speed profile for each slot.

Seems like your theory is true. I did as you said and it works. Now it runs at 1600MHz instead of 1866, but it runs full 16GB! Thank you so much, I owe you, big time!

 

[BadAsAl]

Great to hear, and glad to help! And thanks for trying this so I can let others know it worked for you.

 

[BadAsAl]

BTW running at 1600 versus 1866 will not affect performance enough to notice so I wouldn't worry about getting it to run at 1866.

 

[MarkusL90]

BTW running at 1600 versus 1866 will not affect performance enough to notice so I wouldn't worry about getting it to run at 1866.

Hey thanks for the additional info! I was about to ask about that as well since I'm using my PC more for Photoshop (I'm a concept artist/designer) than gaming. Awesome, I really couldn't be happier!