@frogone - You’re welcome! Try it in FAT too. Some are just not compatible no matter what. No, it’s not a security thing, just compatibility with memory chip or controller insider the USB sticks.
No problem to have other USB stuff installed, but do check your manual, some boards have a specific USB port you need to use for Flashback. On these older models, I think it was the one under Ethernet port
So an update (or lack-thereof!) - I’ve now tried several USB sticks ranging from 256MB, 512MB, 2GB, 4GB in FAT and FAT32 and I’m still getting the same result (no where). On pressing the flash button on the back of the PC the blue light flashes 2-3 times and then goes steady blue. When it goes steady blue the light (if installed) on the USB key extinguishes.
I’ve done a full format on each key and only have the .cap file on it. I’m truly stumped as I have successfully flashed the board in the past using a USB stick…
I’m wondering should I just try and flash the board only with all components disconnected, it’s a fair bit of hassle and really shouldn’t be required in theory. If anyone could suggest a make/model of USB key that they’ve used to successfully flash this board please let me know, thank you!
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Could you elaborate?
read back starting with page 1
Are you referring to the Compatibility Support Mode feature to be disabled?
Well if know the procedure and have done it already before…i suggest u do a hard reset to the motherboard and disconnect devices/gadjets.
And the rest u already know… different USB sticks (smaller as possible), correct USB port, power in stand-by mode, FAT16/32, correct.cap name.
Other from this…hw failure in BiosFlashBack fucntion? Everything is brand new once in a lifetime…
Well I thought I’d send another (embarrassing) update. In my haste to get my NVMe drive up and running I missed out two letters and I was using the wrong BIOS update. My board is the P9x79 WS. Hence all along the board wouldn’t accept the BIOS I was trying to install. I found the correct BIOS and it’s working like a charm booting from Windows 10.
I was running Windows 7 but I was getting a BSOD due to some hardware it didn’t like so I’ve installed Win 10 on the NVMe drive. I was getting a 0xc000000e error on boot-up with Windows 10 but peculiarly if I went into the BIOS and then started the computer from there (exiting the BIOS) the PC would boot fine. I turned off Fast Boot and the PC boots with no issue, so if anyone runs into that issue that might be a work around.
Thanks, it works. Few bumps on the road but it works. I’m writing this just as ADD-ON from guys that made it work 
I can say there are lot of “variables” that can delay you from making nvme bootable device trought PCIe for MBO ASUS P9X79
Step 1: Check your bios version (while booting press Delete or F2 button to get into BIOS)
"*If your BIOS version is 1203 or older, please install the BIOS Converter and then the converter will update BIOS"
You can do that from official Asus site asus.com
Step 2: Quick format some USB to FAT32 (right click on it then format)
Step 3: Copy it on USB drive and try flashing BIOS with EZ FLASH using Asus Utility or by Inserting USB in White USB connector near Bios flash button (for both you have youtube tutorial)
Step 4: Use that P9X79.CAP from Page#1 post#2, In my case I got error trying to flash it trough Asus Utility so go for step 3 Bios flash button option
Step 5: Turn off that CSM
If you get Graphic card error like some users:
1. Install GPU-z and extract your Graphic card bios (if UEFI box is blank) change bios using some other tutorials to enable that UEFI on your card or replace graphic card for newer.
Step 6: Make correct boot order and install Windows 10 or desired using instructions given on page one
quote:"Make sure to convert all your drives from MBR (Master Boot Record) to GPT (GUI Partition Table) or the UEFI enabled OS won’t ‘see’ the MBR partitions."
Enjoy.
Hi Guys, long time lurker, first time posted, is there any chance someone still have th 4701 version with nvme suypport? the DL link is dead.
Lost_N-BIOS, you are amazing.
Hi guys,
I also got a P9X79 plain and I’m gonna try my first modded bios flashing.
@Lost_N_BIOS Is there any version including the pci express bifurcation and NVMe support for the P9X79 plain ?
EDIT : found it in the post #98, you provided a link with bifurcation included. My mistake
With an ASUS m2 hyper adapter (4 NVMe maximum) is it possible to make a Windows RAID with the NVMe installed on the Adapter ?
Regards,
Chris
Hi, unable to flash with the file from post#2 p9x79.zip–>p9x79.cap, using Asus EZ Flash utility from the bios. When it read the file, it reject with "security verification failed" error. I tried flashing from bios 4701 and 4801, same result. I try pushing the bios ( the .cap file on a usb stick - either fat32 or ntfs) with the flash botton being the mobo, on flash then it stall, no update at all. Please share a new file or tell new guideline to install the bios to support booting with NVMe SSD on a Pcie x4 raiser. Thanks for you help
The use of CAP MOD bios files always fails under EZ due to to be a mod and the original bios was modified.
The easiest and most secure to flash the MOD is by the Asus USB BFB feature, so get a working USB drive, sometimes is needed to do a full CMOS reset and/or disconnect additional devices.
Test with the original CAP until u get a working USB, then flash the mod.
Just read previous post and ull find that ur not the only one that encountered this issue and as u can see no miracle was provided, so take the guidance from past users experiences.
@Lost_N_BIOS : The Link of the Bios 4701 for p9x79 nvme boot support in #98 is broken. Can you re-upload it? Vielen Dank 
@mikehue
Lost has been away since January, his private links cant be recovered.
Latest bios is 4801 beta, witch version u want the mod?
EDIT: Ok then 4701… ill post it in a while.
EDIT: Here u go, 4701 NVMe mod.
EDIT: Use Tor browser or VPN, its ur country restrictions.
Hi friend, MeatWar wrote there , to download it two options , but i write 3th Opera browser with VPN Activated …
Here is the MeatWar (thanks to him) file :
https://www.mediafire.com/file/ucdd4b6pz…-2021).zip/file
Regards
Thank you very much Hancor!
I’ve bought a new NVME SSD and thanks to your BIOS, it works like a charm! 
