is your os installed with raid5?
if yes install os very basis with one ssd for example.
use bios 1701.

will not post or will not boot up? unsure why you have been told to install windows 7 by an asus tech if it doesn't post, well it wouldn't surprise me at all but let's get things straight 1st 🙂

I have windows 10 installed 2x Titan X working perfectly so it can be done no problem...not an OS thing.

Things to check...

remove anything else from PCIe lanes. Try one card at a time in first red slot. Then try one card at a time in third red slot. If same card fails both slots it's the card. If same slot fails both cards...it may be board or CPU since controller is on CPU.

If both cards work separately try different SLI bridge

What PSU do you have? is GPU EZ plug for additional power plugged in....are you powering cards with separate cable to power inputs or running a ribbon cable to power both inputs on one card? Are 8pin 4pin and 24pin ATX power connections checked and connected. Have you tried reseating CPU?

Are PCIe lane switches "on"...are lights on next to occupied lanes?

Does the board stop at a particular post code

Have you updated board BIOS...tried second BIOS

Have you tried clean OS install?

From what you describe, I'm betting this is almost certainly a result of insufficient power from your PSU.

"From what you describe, I'm betting this is almost certainly a result of insufficient power from your PSU. "

Or insufficient power to the PSU from the wall/power strip. Make sure the computer is not sharing power with other devices like monitor or printer.

"EZ-Plug" happens to be a standard 4-pin molex, the sort used for clunky old floppies and HDDs. ATX specs still require a minimum of one of these output connectors on every PSU - modular PSUs probably include a few adapters in the box.

lol, Asus chose this connector because it is always present and almost everything runs off SATA power these days so it's rarely used.

You could splice any 12V power/ground into the EZ-Plug, but modifying the PSU is serious business and probably voids warranty on everything you plug it into. If you don't have the correct connector then you should purchase a $2 adapter cable or a different PSU.

One thing that's been bugging me about this EZ plug thing is that I've had stability problems (at idle, not load) for quite some time. I picked up an X99-PRO and the PSU, CPU, RAM and even SLI 980's all run just fine in the X99-PRO, but the R5E is freezes randomly over night (though never under heavy load).

Here's where I am really confused: The X99-PRO not only does not have the EZPlug, but it does not have the additional PCIe 4 pin connector. So the SLI 980's get their juice from directly from the PSU.

I realize that this likely means my R5E is just defective, but I am wondering why the R5E is using 2 additional connectors when even overclocked the X99, does not appear to require them? That and this EZ plug is not exactly a high-current connection by the gauge of the wire, so where exactly does this go and what is relying on it?