The attached BIOS is the latest version (1902) for the ASUS X299 Prime Deluxe I (not II) mobo.
The attached, modified BIOS uses the image below as a replacement for the ASUS stock image. I've been using this modified BIOS for a few weeks and it works well and is completely stable (unlike earlier BIOS releases for this mobo).
(In fact, I'd about given up on this mobo, but decided to give it one more go before moving on; this new BIOS was the ticket.)
I prepared the BIOS following the instructions laid out by KGP on the first post of his massive thread (I didn't quite like his image, nor that version of the BIOS). I re-sized the chosen image in an iterative process to maximize the size in order to fit in place of the stock ASUS image. I believe the image was created by someone known as Howiedi2.
This BIOS is flashed as per the ASUS manual. Before flashing, please duplicate (to keep a copy) and then rename the duplicate file to
X299D.CAP prior to use.
Of course, after flashing, you'll need to either re-enter proper BIOS settings (if upgrading from an earlier BIOS), or, re-load previously saved settings (if re-flashing the same version), before booting into the Mac OS.
Again, the attached BIOS is ONLY for the ASUS X299 Prime Deluxe version I mobo. As with all posts regarding BIOS, use at your own risk.
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EDITED 23 Sept 2019 (last updated: 23 Sept 2019)
added more modified BIOS (latest versions) for various X299 mobos. Listing to date:
ASUS X299 Prime Deluxe (I)
ASUS X299 Prime Deluxe II
ASUS X299 Sage/10G
ASUS X299 ROG Rampage VI
ASRock X299 ITX/ac
ASRock X299 Extreme 4
ASRock Fatalty i9 XE
Gigabyte X299 Designare EX
This may not work for any GB mobo: I only have a GB Z390 Designare to test. I tried various image sizes, including the exact same size as the GB logo. Each time when I tried to flash the BIOS, I got "Invalid BIOS Image" error, and wouldn't flash. This may be due to an internal "Security Flash Check", which may prevent a successful flashing of any modded BIOS.
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I downloaded the latest version of each BIOS from the their respective manufacturer's web site, and then substituted the image below for the stock image.
Remember to re-name each BIOS as per the manual for the respective mobo prior to flashing.
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