I believe I'm facing a similar issue with the X99E-ITX/ac motherboard. Here is the configuration I've got:

CPU: Intel Xeon E5-2658 v3

RAM: Samsung DDR4 2133MHz 2x16GB ECC Reg

SSD1: Samsung SM951 512GB AHCI

SSD2: Samsung 850 Pro 1TB

Video: ASUS GeForce GTX 970 DirectCU Mini 4GB

ODD: Pioneer BDR-XS06JL

I'm trying to install Windows 10 Pro 64-bit on this system, but keep failing miserably. The installer just keeps hanging at the initial stage when there is the Windows logo on the screen. I've tried virtually everything: setting the UEFI parameters in different ways, installing from the ODD and from a USB drive, physically switching off each of the SSDs, etc. Nothing helps. I'm using the latest BIOS version which is P3.60.

One thing I've noticed is that my processor is not in the list of compatible CPUs - strictly speaking, this model is meant for embedded systems. However, it's the same Xeon E5 CPU in principle, so I cannot see a reason why it shouldn't work.

I've invested quite a bit of cash into this config, so I really want to make it work. Does anyone have an idea?

I'm a bit sad having bought all the parts last week and put everything together to run into this same problem. Same X99E-ITX mobo, same bios version, and same issue with not able to install or boot into any modern OS. I'm using ECC ram as well, but Kingston brand.

Any insight would be greatly appreciated. Thanks!

 

I've submitted my case to the ASRock tech support.

 

Does anyone know what to expect - will the response be quick, soon or any at all?

 

Thanks.

Thanks so much again for your attention.

 

The ASRock X99E-ITX/AC has only 2 memory slots. They were populated with 2x16GB Corsair non ECC ram which worked. When swapped with 2x16GB Samsung ECC ram (which ASRock claimed on the memory support list as supported), Windows failed to boot normally, only in Safe Mode.

 

Next booting Windows x64 installation DVD, connected onto SATA port (not a USB external DVD drive), Windows x64 for Windows 7, Windows 8 and Windows 10 failed to boot. For Windows 7 it froze with Winlogo & "Starting Windows" . For Win8 and 10, those round wheels the spin on bootup, well they stuck/stop spinning :(

 

I tried pulling all HDD and putting just 1 blank HDD (Samsung 250GB drive formatted but empty) and booting the Windows installation medias, still no luck.

 

As far as I know ECC/non-ECC is a hardware mechanism, transparent to the OS. But certain information is forwarded to the OS such that it appears in Device Manager. I suspect something is buggy there. There is no BSOD or Black Screen, just frozen.

 

And the ASUS X99 board, has identical processor and runs Windows 7 x64, just using memory slots A1 and B1, rest are empty. Both Asrock and Asus machines have Win 7 x64 updated to the latest updates (SP1 and Dec 16 rollup from Microsoft).

http://event.asrock.com/tsd.asp

In the mean time, what OS is installed (that works with non-ECC)? 

If you are able to start in safe mode then the issue is almost certainly software. I am guessing you are not using windows 8 or higher as the only way I know of to enter safe mode on those OSes is by using MSconfig.exe from within the OS and flagging it for next boot. 

Would I be correct in guessing the OS on your ASUS board is a higher version? Windows 8 and above handle drivers differently to prior versions and most likely include support for easily interchangeable parts like RAM and CPU.