Some PC users have an understandable fear about the process of performing a BIOS update. Although it’s rare for a PC to not boot back up after a BIOS update, it does happen, and it’s common to have a little trepidation as you commit to an update.
First, you should know that problems with BIOS updates are much rarer than online forums might lead you to believe. More importantly, they’re often completely recoverable, especially with the powerful built-in recovery tools available with your ASUS motherboard. Some boards are only built for perfect-world updates. We’ve designed our hardware for real-world scenarios. Here’s what you need to know about the process of recovering your hardware in the event of a problem during a BIOS update.
Your first line of defense: clearing the CMOS
To recover your motherboard, the first and easiest thing to try is to clear CMOS. The CMOS is a small chip on your motherboard that stores BIOS settings, like the time, date, and hardware configurations. Sometimes, a BIOS update can leave behind incompatible settings that prevent the system from booting. Clearing the CMOS simply erases these settings and reverts them to the factory defaults.
You can do this in three ways, depending on your motherboard:
- Clear CMOS button: Many ASUS motherboards have a physical Clear CMOS button. Power off your PC, unplug the power cord, and press the Clear CMOS (sometimes labeled “CLR_CMOS”) for roughly 5-10 seconds. Then, plug in your power cord and power on your PC.
- CLRTC Pin: Some ASUS motherboards offer Clear CMOS functionality through a two-pin header marked CLRTC. Power off your PC, unplug the power cord, and place a jumper cap on these pins for about 5-10 seconds. Remove the jumper, plug in your power cord, and turn on your PC. If you don’t have a jumper, you can briefly touch both pins with a metal object like a screwdriver for about 5-10 seconds. (Before doing this, be sure to ground yourself by touching a metal part of your PC case to discharge any static electricity.)
- Remove the CMOS Battery: If you can’t find the jumper, you can achieve the same result by carefully removing the CMOS battery. Power off your PC, unplug the power cord, and find the CMOS battery. It’s a small, silver, coin-like battery from the motherboard. Remove it, wait 2-3 minutes, and then put it back in. Plug in your power cord and turn on your PC.
For many minor issues, this simple reset is all that’s needed. If the CMOS clear was successful, your PC will now boot to a prompt alerting you that the BIOS settings have been reset. We recommend following the prompts, selecting F1 to enter the BIOS setup, then F5 to load optimized defaults. Once you’ve confirmed that your system is now back online and stable, go ahead and apply any further optimizations or tweaks.
When clearing CMOS isn’t enough: understanding your tools
If clearing the CMOS didn’t work, it may mean the BIOS firmware itself is corrupted. This is where the distinction between our recovery tools becomes important.
Comparing Clear CMOS vs BIOS FlashBack™: Clearing the CMOS is like performing a “factory reset” on your TV’s settings. It resets your preferences but doesn’t change the underlying software. ASUS BIOS FlashBack, on the other hand, is like reinstalling the entire operating system on your motherboard. It completely overwrites the old, corrupted firmware with a fresh, updated copy.
If your motherboard won’t POST because of a failed update, and Clear CMOS doesn’t fix the problem, BIOS FlashBack™ may be the answer that you’re looking for.
How to use BIOS FlashBack to restore your firmware
ASUS BIOS FlashBack is a hardware-level feature that lets you re-flash the BIOS with just a power supply and a USB drive. You don’t need a CPU, RAM, or GPU, which makes it perfect for recovering from a state where the PC won’t boot.
Here’s a brief rundown of the process:
- Use a different PC to download the necessary files. Go to the ASUS Support page, search for your specific motherboard model, and download the latest BIOS file.
- Prepare your USB drive. Format a USB drive to FAT32. Unzip the downloaded BIOS file and run the “BIOSRenamer.exe” tool. This will rename the .CAP file correctly. Copy this renamed file to the USB drive.
- Prepare your motherboard. For the highest chance of success, we recommend disconnecting components from your motherboard except for the main 24-pin and 8-pin power connectors. This ensures no other hardware interferes with the process.
- Find the BIOS FlashBack port and button. Plug the USB drive into the USB port on the rear panel of your motherboard specifically marked “BIOS.”
- Start the recovery. With the power supply on, press and hold the BIOS FlashBack button for three seconds. A light will begin to flash, indicating that the recovery process has started.
- Be patient. This will take several minutes. The light will flash, and when it stops, the process is complete. Your BIOS has been restored. You can now reassemble your PC and boot up normally.
More help is always available
This guide should help you recover from most BIOS-related issues. But we want to be clear: you’re never on your own with an ASUS product.
If you have tried these steps and still need help, please visit the ASUS Support page. There you will find a comprehensive library of guides, FAQs, and, most importantly, ways to contact our dedicated support team. They’re ready to help you through any remaining issues.
At ASUS, we believe a great product is one you can count on, especially when things don’t go as planned. Features like BIOS FlashBack™ provide you with peace of mind and a clear path to recovery, ensuring you can build with confidence.