AMD Ryzen ‘Zen 3’ CPU Support Enabled on ASUS 300 Series Motherboards Using BIOS From ASRock’s 400 Series

ASUS ROG forum members have found a bizarre way of enabling support for AMD Ryzen ‘Zen 3’ Desktop CPUs on their ASUS X370 series motherboards using BIOS from ASRock’s B450 boards.

AMD Ryzen ‘Zen 3’ CPU Support Enabled on ASUS X370 Motherboards Using BIOS From ASRock’s B450 Boards

It’s quite mind-boggling to see people going to these extends to enable support for a certain line of processors on their motherboards that aren’t officially supported. The main issue is that AMD itself had blocked motherboard manufacturers from offering Ryzen 5000 ‘Zen 3’ Desktop CPUs support on older X370 motherboards. This meant that users of ASUS motherboards & various other brands were cut off from a generation of processors which they were initially said to get support for.

AMD Ryzen 5000 Desktop CPUs Available At Discounted Prices At Major US Retailers – 12 Core 5900X For $499, 8 Core 5800X For $393, 6 Core 5600X For $272

Now X370 motherboard owners, particularly from the ASUS brand, have found a way to cross flash their X370 & B350 motherboards to their X470 / B450 equivalent. But here’s where things get more interesting. Not only are the older 300-series boards being cross flashed with new 400-series BIOS but the ASUS 300-series motherboards could be cross flashed with ASRock 400-series board BIOS and work like a charm.

Short instruction how to get Zen3 support on this motherboard [ASUS ROG Crosshair VI Hero, X370]

  1. Download archive –
  2. Unpack archive to some folder and create usb bootable flashdrive using rufus-3.13p.exe, copy afudos and bios.rom to bootable usb flashdrive
  3. Boot from USB drive and type in command line: afudos bios.rom /gan
  4. Wait until flashing process come over and reboot the system, install Zen3 CPU

You can always flashback to original bios using flashback button (just make sure that you have some older CPU to boot up)

Note: Bios is from Asrock b450 Pro R2.0 (v 4.50), do not update it to newer agesa if you have Zen3 CPU

If you have Zen2 CPU and want to get SAMResize bar support – update bios to v4.80 Agesa (download bios from Asrock website)

Further information from Forums reveals that ASRock 400-series BIOS works best with ASUS’s 300-series motherboards. Flashing BIOS from Gigabyte and BIOSTAR 400-series line renders the PC unusable since the PC is unable to boot. Flashing the ASRock BIOS though lets you boot through SATA drives and AMD Ryzen 5000 ‘Zen 3’ chips work without any issue though you do lack NVMe support and resizable-BAR.

ASRock also silently released AMD Ryzen 5000 ‘Zen 3’ CPU support for its 300-series lineup and you can see that even their older X370 BIOS can be used to enable support on ASUS’s 300-series boards while retaining NVMe support.

ASRock bioses have no Re-size BAR support, Gigabyte bioses have no POST (even it was reported semi-working before), Biostar Bioses support Re-size BAR and it works, but they have nasty Cold boot bug except X470 GT8. It boots great from cold start, re-size BAR works, Fan works weird for this rom. Windows apps like Fancontrol or Argus Monitor can adjust speeds but fan speed values works opposite. 0% on app makes 100% for fan, %50 and %50+ on app makes 0% for fan. This X470 GT8 bios has a weird bug. PCI Express 3.0 x16 slot works at 3.0 8x. This is the only bios that does PCI-Express speed lowering to half.

via OCN

Well, this is good news for users who have been waiting to find a way to run the brand new AMD Ryzen 5000 ‘Zen 3’ Desktop CPU on their still, highly-capable, ASUS ROG 300-series motherboard. The ASUS ROG Crosshair VI HERO was the first ROG AM4 motherboard and still holds potential so there’s just no excuse to keep it limited to Zen 2 Desktop CPUs. Users can be seen running various Zen 3 CPUs on the motherboard with this cross flashing method and with the CPU lineup available at discount, there’s no stopping users from getting a brand new chip for their old yet still trusty 300 series board.

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