Hello Fernando,

thank you very much for your support and support for finding and setting up a suitable SSD and creating a required BIOSmod for my system.
The PC is now ready and running well.

Board: MSI Z77 MPower
M.2 SSD: Samsung NVMe 960 EVO 250
BIOSmod: 17.12 + NVME module 3, uncompressed
Adapter: Aquacomputer kryoM.2 evo PCIe 3.0 x4 Adapter for M.2 NGFF PCIe SSD
The LED lighting integrated into this adapter provides an information at the
Access to the M.2 SSD, since the SATA access LED does not work.

Sorry again for the run-up difficulties with the English language. The Google translator works much better than the previously used Bing translator.

Sincerely
Carnmerioneth

AS SSD Benchmark 5 GB:
Samsung SSD 830 960 EVO
Lesen Schreiben Lesen Schreiben
Seq: 502,69 MB/s 258,55 MB/s 2398,24 MB/s 1580,63 MB/s
4K: 17,94 MB/s 54,59 MB/s 40,29 MB/s 123,61 MB/s
4K-64Thrd: 280,54 MB/s 82,25 MB/s 1754,34 MB/s 816,72 MB/s
Zugriffszeit: 0,156 ms 0,258 ms 0,041 ms 0,159 ms
Score: 349 163 2034 1098
Score gesamt: 683 4129

Hello everyone!
I have ASRock b250m Pro4 motherboard and PLEXTOR 512M8PEGN PCI ssd. If any HDD connected I can setup and load Windows 10 from ssd. If I disconnect HDD (PC has ssd only) system start loading and cycle reboot. This behaviour I see also when load from USB-flash - system load normally only if SATA disk connected. Could you help me? I need PC with nvme ssd bootable disk only. PC has 16GB Samsung DDR4 2400 memory (it tested by memtest - is OK).

Hello Fernando!
1. Due to specification ASRock b250m Pro4 mainboard supports NVMe SSD as boot disks http://www.asrock.com/mb/Intel/B250M%20P...p#Specification.
2. There is only one bootable disk (NVMe SSD) connects to the mainboard.
3. Yes, I looked the "Windows Boot Manager <PLEXTOR>" in the boot section of BIOS.

If PLEXTOR NVMe SSD is connected only the PC cannot boot - it begins booting and reboot, try booting again and reboot one more and so on. In this configuration PC can't boot from USB flash too.
If I connect a SATA HDD (it may be empty - without any volumes) the PC boot from SSD or from USB flash well. I don't know how to get bootable PC with single NVMe SSD. Do you or any other forum participants encounter the same situation?

Using system: MB: ASRock B250m Pro 4, CPU: Intel Pentium G4600, RAM: 16 GB SAMSUNG DDR4 2400, Disk Drive: 512 GB PLEXTOR 512M8PEGN, Graphics: Intel HD Graphics 630, OS: Win10 Pro x64

I tried to boot another system with this SSD (ASRock Z170 Extreme, single PLEXTOR 512M8PEGN). There is no any problem. System started well. But my mainboard has strange behaviour described above. What do you think - this is mainboard defect or specific property? I have no any other problem with this mainboard.

@pVlady
Did you try both M.2 slots? The upper M.2 slot (M.2_1) will share resources with the SATA ports, which will make the M.2 SSD run slower when another drive is present in SATA3_0. Try the lower M.2 slot (M.2_2) as it will not share resources with other ports.
And like Fernando mentioned, check your BIOS settings. Connect only the M.2 SSD in the lower M.2 slot (M.2_2), and in the BIOS check “Advanced/Storage Configuration” to see if your M.2 SSD is detected in “M2_2”. If it is, check “Boot/Boot Options Priorities” to see if your M.2 SSD is selected as the default boot device. Looking at the manual at the link you provided it shows “Boot Options Priorities” but doesn’t show details, so I’m assuming clicking on it will give you options.
Also, check if there are any BIOS updates available for your motherboard. It looks like version 2.10 is the latest available.
There is no reason that I know of that would cause your motherboard to do what you say it's doing, other than the boot priorities. But when installing Windows 10 on this M.2 SSD you should not have any other drives connected in the system, as Fernando's guide says. So, if you initially installed Windows 10 with the SATA drive installed with the M.2 SSD, you need to start over without the SATA drive (or any other drives).

@Paulos7
Thanks for you answer.
1. Now ssd is connected to M.2_2 for the same reasons that you pointed out. But I trtied both slots (M.2_1 and M.2_2) and result was the same.
2. The NVMe ssd is single disk in the PC. I see that SSD is detected in M2_2 on the Advanced/Storage Configuration tab. I see "not detected" for all SATA ports.
3. I see "Windows Boot Manager <PLEXTOR...>" in Boot/Boot Option Priorities and PLEXTOR as default boot device. There is no other device in the system.
4. Then motherboard UEFI BIOS has 2.10 version. (I don't try 2.11 because it is beta and updates Hyper-Threading only. A tried to disable Hyper-Threading but has no success).

In the configuration mentioned above the PC does not boot. If I install SATA HDD (simply connected to SATA without any volumes on it) the PC boots nomally.
Also the PC does not boot from USB flash with Windows ISO if there are no SATA connected (if system has NVMe ssd only). In this sitiation I NEED connect empty SATA HDD to install witdows on SSD. Of course, HDD was visible during windows installation (when I choose disks) but I don't use it. All partitions (efi, resore, system) was created on SSD. The HDD remains empty and has now volimes.

P.S. The changing of CSM settings on Boot/CSM tab or setting CSM to disable does not solve the problem.
P.S.2 If I remove ALL ssd and HDD than the PC boot from USB flash with Windows ISO and I get a message that system has no ane disks and proposal set drives. The system doesn't boot from THIS USB flash if SSD connesned in any M2 slot (cycle reboot after 1-2 second when "Stating Windows" is displayed).

Is there defect of motherboard or specific property?

@Fernando
Thank you for you opinion.
I wrote a letter to ASRock Technical Support and waiting answer now. I'll write about ASRock expert report when get one.

@pVlady
The initial Windows 10 installation needs to be done without any other drives connected, or boot configuration files will possibly be written to the SATA drive, making it necessary to have that drive connected for Windows 10 to boot correctly. If the USB with the Windows 10 ISO is not prepared correctly, it will not work.
Did you use Rufus to create the Windows 10 USB install media formatted as GPT/UEFI and FAT32? If so, try putting it in a USB3.0 port (with only the Plextor SSD connected) and press F11 while booting to bring up the ASRock boot manager, and select the USB drive in UEFI mode. It should boot into Windows setup normally.

My ASRock motherboard is older than yours, but though my BIOS shows “Samsung SSD 960 EVO 250GB” in Boot Options Priorities, I have to select “Windows Boot Manager” as the first bootable device for Windows to boot successfully. If I select “Samsung SSD 960 EVO 250GB” my PC will not boot. “Windows Boot Manager” will only show up in the BIOS boot section after Windows has been installed on the SSD (obviously).
If you installed Windows 10 to the Plextor SSD without a drive in the SATA port (and the USB formatted as GPT/UEFI and FAT32), try changing the 1st bootable device to “Windows Boot Manager”, not PLEXTOR.
I personally don’t think there is a problem with your motherboard. I think it has to do with the way Windows was installed, or a BIOS setting, or both.

Hi... i have a problem. I have buyed an Asus Hyper M.2 x4 Mini card, for place the ssd samsung 960 PRO 1TB on the pcie x16_4 instead of the native slot on my ASUS Z97-WS. I have the necessity to place the ssd on the PCIE slot, because if i use the M.2 disk, i can't use the SATA6G_5, SATA6G_6, SATA6GE_1 and SATA6GE_2 slots of the motherboard, because they share the same bandwith of the M.2 slot, and enabling the M.2 slot automatically disable the sata slots. Now the question is:

I see that the z97 chipset is supported by the m.2 hyper card and the Asus support, confirm this, but when i insert the M.2 in the pci express card and in the slot the M.2 card is not visible and i can't install the OS on this M.2. The problem isn't on the slot, because with other cards works well. When i turn on the pc with the card inserter, appear a green led on the card. The card work. I think is a problem of settings, but i have tried various settings, but the SSD M.2 is invisible. If i use the SSD in the native M.2 slot, works well. How i can solve this?

Hi... thanks for the reply. I have contacted Asus and the guys from the supports tell me that the the Z97-WS fully support the Hyper M.2 Card, without any mod to the bios. The 960 PRO on M.2 slot works well but for the problem that i mentioned early, i cannot use the M.2 slot. Now tell me if i have to mod the bios. I have tried to unplug all the discs from the motherboard, but the ssd pcie isn't visible. I know how to create the bootable pen drive in UEFI mode with rufus, because it isn't the first time that i have to install an UEFI OS.

I have tried with WIN10 and it's the same. I have integrated PCIE drivers on WIN7 ISO for install PCIE SSD.