Just a thought - I don’t have anything really concrete to stand on -
The rank of the memory modules can make a difference. Quad rank is cheapest, then dual rank, then single rank. Intuitively, the memory controller can only drive certain maximum of “total” ranks added together … Maybe your motherboard can only “drive” eight ranks, and maybe the chips you’ve got are quad-rank, so it can only drive two chips total. Check it out, try looking up your DIMM module name on the Kingston site and see what rank they are, and try to find out what rank the G.Skill modules are. This could be the problem.
When I had 16 in, the BIOS would only recognize 4. Go into Linux and type free, and yeah, you’ve got 16. Allocate 14GB of pinned memory, yeah, that works, so…
The motherboard manual for the Destroyer only claims that it supports 8 GB. If nothing else, you should probably warn people on the build-your-own-page that 16 GB of memory is not officially supported in this motherboard.
I don’t know if this has anything to do with it, but when I built my last personal-use computer, the Intel motherboard I used supported up to 8GB of RAM, but only if it was DDR 533 or 667; if I used DDR 800 (I did), then it only supported up to 4GB…I don’t think this was ever fixed either (meaning it may just be a limitation of that particular board).
I wonder if the foxconn has the same issue…it should say in the motherboard manual.
ps: P14 fixes the bug where having four four PCIe slots filled reduces the peak bandwidth to each card by 40% or so, you should definitely be running that BIOS anyway. (didn’t know it was officially out yet)
I did it once… I think I used a NVS 285 or something in the PCIe x1 slot. I seem to recall that I couldn’t get a PCI card to work, but I don’t remember.
It is a hassle because you can only drive one card off of the rail that has the 2 PCIe 6-pin connectors, so you need to take the bizarro 10-pin connector, jam a 6-pin to 8-pin adapter where the keying lines up, and then power the second card. That works fine. (Major props to my coworker for figuring that one out…)
T7400 only has two PCIe 6-pin connectors coming directly from the PSU. I wouldn’t call 2xC1060 on T7400 “supported” unless you get the Dell 10-pin to PCIe 8-pin connector, but it does work. There’s one proprietary ten-pin connector in the T7400 where six of the pins are keyed to a PCIe 6-pin connector, and there is sufficient power to drive 2xC1060s. If you put a 6-to-8 pin adapter on that connector, you can power the second C1060 while the two 6-pins power the first. It should be very straightforward if you have the connector, but I didn’t (apparently whether or not you get it depends on your configuration from Dell).