Gigabyte 990fxa-ud3 rev4.0 can't do two dual channels?

[AgentFXA]

I am puzzled this board obviously can't do two dual channels - here 4 HyperX ram sticks (16GB/8GB) but only 1 pair is dual channel and the other pair is single according to CPU-Z!?

Anyone got this board running in two dual channels?

I would expect both ram sets to be in dual mode

[Tiger]

Memory manufacturers do not guarantee that mixing together multiple kits will work.

What you are doing can be viewed as an experiment on your part. You obviously expected it to be a sure thing.

Such combinations, 4 HyperX ram sticks (16GB/8GB), were never tested together and carry no guarantee that they will work together. Only single kits are guaranteed to be compatible together.

[AgentFXA]

We're talking here about same ram:

1 set is HX318C10FBK2/16
and
1 set is HX318C10FBK2/8

24 GB total... by all means that should do dual-channel on both sets, no?
..and btw it's switching down to 1600 too instead keeping 1866 speed

[rinkol]

Two sets of memory will load the memory controller more than one set - the bios will usually default to a reduced speed to accommodate this behavior. You might be able to set the higher speed in the bios, but I would run a memory test to be sure.

Does the full memory capacity get recognized? I've seen cases where a memory module didn't work because it wasn't completely seated. As a sanity check, make sure that each pair of memory slots comprising a single physical channel has memory modules of the same type. You could try pairs of memory modules by themselves. Finally, there are bios settings (ganged/unganged and dinterleaved) that might make a difference.

[AgentFXA]

Sorry for the late reply but sometimes the Gigabyte email ends up in my gmail spam folder even I whitelist this forum.

Yes, all 24GB are seen by Win7 but only 16GB are permitted due to Win7 Home ram size limitation. I already have switched ram channels but no matter what there is always just 1 channel (2 same sticks) in dual mode. 

[reeven]

i tested this board with:

2x2gb micron 1600
2x4gb hynix 1600
 2x2+2x4
2x8gb kingston 2400
4x8 corsair ddr1600
i even could put 2x8+8 and it sees them as dual channel. Itws required to tested all slots them it worked.

[AgentFXA]

i tested this board with:

2x2gb micron 1600
2x4gb hynix 1600
 2x2+2x4
2x8gb kingston 2400
4x8 corsair ddr1600
i even could put 2x8+8 and it sees them as dual channel. Itws required to tested all slots them it worked.

You confirm that you see two dual channels hence both ram sets are in dual mode concurrently?
Use CPU-Z/SPD tab and check stick for stick being in dual mode. You'll probably find only 2 sticks (of the 4) are in dual.. the other two sticks are in single mode - IF you see all 4 sticks in dual mode then this is what it should be!

Okay, from later today I am away from home for 1 week hence no Internet

[JGB123]

We're talking here about same ram:

1 set is HX318C10FBK2/16
and
1 set is HX318C10FBK2/8

24 GB total... by all means that should do dual-channel on both sets, no?
..and btw it's switching down to 1600 too instead keeping 1866 speed

OP, have you tried installing the pair of 4GB DIMMs in Channel A (the two slots closest to the CPU, which is counterintuitive to the colour coding) and the two 8GB DIMMs in Channel B?

From page 16 of 104 of your motherboard's manual:

"The four DDR3 memory sockets are divided into two channels and each channel has two memory sockets as
following:
Channel A: DDR3_2, DDR3_4
Channel B: DDR3_1, DDR3_3"

http://download.gigabyte.eu/FileList/Manual/mb_manual_ga-990fxa-ud3_v.4.0_e.pdf




Re your RAM being down-clocked to 1600MHz. This is normal when using 4 DIMMs with an AM3+ CPU:

DDR3 memory frequency guide
http://support.amd.com/en-us/kb-articles/Pages/ddr3memoryfrequencyguide.aspx

There's no practical difference in performance between 1866MHz CL13 and 1600MHz CL11 RAM:

Sep 25, 2013
High Speed RAM - Is it Worth it? DDR3 1333MHz vs 2400MHz Test - YouTube
https://www.youtube.com/watch?v=dWgzA2C61z4