MSI X99S GAMING 9 AC - Manual (Page 46)

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BIOS1: Multi-BIOS Switch
This motherboard has two built-in BIOS ROMs (Labeled A and B, default BIOS ROM
is A). If one is crashed, you can shift to the other for booting by sliding the switch.
BIOS A
Green LED Blue LED
BIOS B
BIOS recovery with AFUDOS command
When BIOS updating fails or causes the computer non-bootable, you can recover the
failed BIOS by the steps below.
Preparation:
1. Prepare a bootable USB flash drive.
2. Download the latest BIOS file from the MSI official website at www.msi.com, and
then decompress the file.
3. Copy the AFUDE238.exe and the BIOS file to the bootable USB flash drive
BIOS recovery steps:
1. Power off the computer.
2. Set the Multi-BIOS switch to the functional BIOS ROM.
3. Insert the bootable USB flash drive you have made to the USB port.
4. Boot the computer into the bootable USB flash drive.
5. Set the Multi-BIOS switch to the failed BIOS ROM.
6. Execute the below command to flash the BIOS:
For example: AFUDE238 EXXXXIMS.XXX
7. Restart the computer after the BIOS flashing is complete.
Important
Do not use the Multi-BIOS switch when system is booting up.