Good evening,
I was trying to update the bios of this Asus https://dlcdnets.asus.com/pub/ASUS/Deskt...6630-8-1204.zip

and I tried two ways of updating:
1. ASUS Update https://photos.app.goo.gl/MBvdhs29swBkG6nd9
2. ASUS EZ Flash 2 Utility v01.04 https://photos.app.goo.gl/SQWV5fGtKALEZY2N9

they both seem to not accept the .CAP file
do I need to convert to some other format?

please write down your motherboard model (BM6630?)
well,some bios files are in rom format and some are in cap on that list.
try using ASUS EasyUpdate application from there first
https://www.asus.com/supportonly/BM6630/HelpDesk_BIOS/
you can also try updating your way up,from old to new one by one,or take the risk and use asus biosrenamer and change cap file to rom

the bios image does not match. Is very strange!
https://photos.app.goo.gl/bacfCEKp9SJNR1WS9

indeed,different types of files,its own app is not working, seems like asus does even care,no surprise
start trying them out one by one then,from old to new

@nicovon

There is some notes in bios files from regarding systems Windows 8 ready...the latest bios bios can be only for some revisions of the product, or u can try increased version update as onuracengiz stated.
Do it in built-in bios EZ update...not in OS environment. If it fails in EZ then could be a security warning due to the revision of the hardware, better contact Asus with product information to obtain a new file...

he did try EZ,its not compatible yet,
i have downloaded few of them,some are in cap,and some in rom form,version numbers giving some clue but not enough
disable user account check,disable antivirus and move your way up one at a time

He has to try EZ with incremental version update NOT to the latest 2104...further than that, its for sure a mess from ASUS, as the file serves varies models, the 6630, 6330 and 6230.
His version is 0701 and if the same as the one we can download, its a CAP, so the system has securities/Capsuled.
Do to this, almost sure that the system will not update any ROM file, just CAPSULE files.
Trying ASUS to respond... maybe.
Other possibility...a CH programmer to do a backup and try flash the SPI with higher versions and see how the system responds...or not, his own risk only.

he is already using 0703 (rom) dated 2012/01/06 actually yet there is version 0701 (cap) dated 2013/03/01,that was a part of my point while saying not a good clue
you are right though
although,version 4301 is a rom and dated 2012/12/07 seems like the most recent (cant say if its for you before dissecting it even it says BM6630,cause well, asus /facepalm )