I first read your post in my email client and it really had me scratching my head as to how, apparently, I could get it so wrong in detailing the motherboard and BIOS I had. When I came to the forum I was relieved to see your 'strike-outs'. (Boy that was confusing for a while.)
To clear misunderstanding the motherboard I have is definitely "GA-H61M-DS2 DVI". The motherboard manual can be seen here: https://a248.e.akama...m-ds2-dvi_e.pdf
With respect to memory and Dual Channel Mode this is mentioned on pages 5 (schematic diagram), 7 (under the "Memory" title) and 9 (under the title "Dual Channel Memory Configuration"). Needless to say when it comes to the "BIOS Setup" pages nowhere is Dual Channel Memory mentioned anywhere at all. (Manual is a dead loss in that respect.)
With respect to the BIOS I've gone into the BIOS again and checked the information there, which is as follows:
Customer Code: UM
BIOS Date: 05/05/2014
If I go to the Gigabyte site for this motherboard and click for the BIOS information page then I get the following: http://uk.gigabyte.c...dl=1&RWD=0#bios
Strange thing is that on that webpage it only offers "F3c" BIOS as being the latest for this motherboard (and at that it's a beta). My BIOS "F3g" is fairly well above "F3c" and isn't even mentioned at that webpage - go figure.
With respect to the number of DIMM sockets, there are only two on the motherboard - so there is no way I can be putting the memory in the wrong sockets.
Here is a screenshot of what CPU-Z says of the memory installed on this machine:
CPU-Z Screenshot.png 12.65KB
I'm not sure how to interpret that. It says "Channel #" is "Dual". But "DC Mode" (I assume that means "Dual Channel Mode") is blanked out - so what does that mean?
IOW, you want 1+3 and/or 2+4. Dual-Channel doesn't work otherwise.
Could someone explain what "IOW" means, I don't understand.
In any case, today I managed to complete a web-form with Gigabyte about this so maybe I'll get a response from there. If I do I'll post up the inf here.