[Solutions] MSI Z77A-G43 motherboard infinite boot loop

After flashing the Bios through the M-Flash in the Setup (Bios interface), the computer restarts itself with reboots every 4-5 seconds with a black screen and messages at the bottom right of the screen with the codes 99 B4 A0 A2. The Bios has been badly flashed. It is now corrupted.

What are the solutions ?

Standard solutions:

1. Reset the CMOS. Unplug the power, wait 45 seconds, press the power button to empty the power, put the jumper on the CMOS (2 pins) for 15 seconds (if you do not have a jumper on hand, then connect the two pins with a screwdriver or other metal part). Remove the jumper (warning: never leave the jumper with the power connected!). Reconnect the power, restart the computer. The problem: CMOS only resets the current Bios settings. It does not reinstall the original Bios. This motherboard is one of those that don’t have a backup BIOS (a second parallel Bios), also it does not have a Bios Flashback (the possibility of installing a Bios even if the computer does not start; using a button and a dedicated USB port).

You will have then access to a menu offering two possibilities: to go to the Setup (F1), to continue to Windows (F2). If the PC continues to reboot then the Bios settings are not the problem.

2. Remove the battery from the motherboard. Unplug the power supply, wait 45 seconds. Press the power button to empty the energy. Remove the battery from the motherboard for 10 seconds, put it back. Reconnect the power supply. Restart the PC. Equivalent to the CMOS reset.

3. It may be a device recognition error. Disconnect all USB devices and connections. Restart the computer.

4. It may be a memory problem. Change the location of the RAM. Put only one memory module on the first slot. Change it by another one. Test the second slot, etc.

5. It may be a hard disk problem. Unplug the hard drives. Restart.

Advanced solutions:

Meaning of codes at startup:

B4: access to USB peripherals, content verification. If stuck on B4, something is wrong with one of your USB connection.
A0: Access to hard drives, but no hard drives found.
A2: start ok, power transmission to hard drives. If automatic restart, then connection between the BIOS and Windows flawed. Bios is corrupted.

6. Flash AFUDOS with RUFUS on a USB stick. Default partition (MBR for Bios or UEFI), file system: FAT32, 4MB, quick format, boot disk using FREEDos. Press the “start” button of the RUFUS software. Copy the entire Bios folder to the USB key. Start the computer with the key. If Dos starts: enter C: \> AFUD4234 E7693AMS.M40, where E7693AMS.M40 is the name of the Bios you want to flash.

7. Create a bootable key with HP USB Disk Storage Format Tool. In FAT32 with quick formatting. Copy the Bios to the USB key and make 6 copies of it with the following names: AMIBIOS.ROM, AMIBOOT.ROM, E7693AMS.M53, E7693AMS.M53.ROM, E7693AMS.ROM, M53.ROM, SUPER.ROM. Where E7693AMS.M53 is the name of your Bios. Restart with the key.

Universal solution:

8. There is a 80% chance that nothing will work because the Bios is severely corrupted. In this case, we will have to move towards a manual and external reprogramming of the Bios (we have to flash the Bios with external access). This solution should work for everyone. Unless you had a lack of luck and your Bios has burned after M-Flash (which is unlikely). See this guide: Guide to flash a Bios with a SPI CH341A mini programmer. That’s what worked for me. And that was the handling made by MSI to recover bricked motherboards at the time when the motherboards were still under warranty.

Default solutions:

9. Redeem a used MSI Z77A-G43 motherboard (100 dollars on average, not including postage). But with the risk of having anĀ obsolete motherboard or that presents the same risk of corrupted Bios.

10. Buy a recent ASUS ROG MAXIMUS X APEX (which has the Bios Flashback button to avoid the corrupted Bios problem; 300 dollars on average, not including postage), with a recent processor like the Intel Core i7-8700K (315 dollars on average, excluding postage). Your old memory (DDR3) will not be compatible anymore. It will therefore be necessary to add DDR4 memory modules (90 dollars for 8 GB, 180 dollars for 16 GB, not counting postage).


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