Fix: CPU Not Detected

Will your computer not start up because the CPU can't be detected? Here's a short guide that explains how you can fix the CPU not detected issue.

You’ve probably heard that building a computer is easy or simple. And sure, it is, but mistakes are always possible, especially if you don’t have any experience in the field.

One of the worst things that can pop up on your screen after building your PC is “CPU not detected”. Your computer won’t POST if you don’t fix this issue.

Don’t worry. This error message does not mean that you’ve broken your CPU. Instead, here are a couple of solutions you can try before replacing the processor.

Let’s fix that CPU!

Related:How To Upgrade A CPUFix: CPU OverheatingWhat Is CPU Bottlenecking?

Table of ContentsShow

Fix 1: Reset BIOS

Whenever a CPU cannot be detected, there are only a couple of causes. Either there’s something wrong with the BIOS, the motherboard, or the CPU itself.

But, usually, it is the BIOS. Fortunately, this is the easiest thing you can test and fix, so we recommend trying this fix first.

Here’s what you can do to reset the BIOS:

  1. Completely turn off your PC and turn the PSU off too.
  2. Remove the case side panel.
  3. Now, start looking for the CMOS BIOS battery. It’s a circular-silver battery, so you should be able to spot it quickly. If not, it may be hidden behind the GPU, so you’ll have to remove that too.
    CMOS BIOS battery
  4. To remove it, press the metal tab on the side, and it will pop out. Again, use MSI’s B550 image above as a guide.
  5. Leave the battery out for a couple of minutes to ensure any power in the motherboard is completely drained. After that, put the battery back, and the BIOS will be reset.

This should fix the CPU detection issue. If not, try the next fix.

Fix 2: Reseat CPU

The CPU can fit into its socket only in one way, so it won’t be detected if it isn’t properly seated. You will need to reseat the CPU to resolve that.

  1. Unplug the CPU cooler.
  2. Unscrew the cooler and remove it.
  3. Slightly press on the metal handle on the socket and then pull it upwards. This will release the CPU.
    releasing CPU
  4. Check if any pins on the socket (Intel) or CPU (AMD Ryzen) are bent. If they aren’t, look for a small golden triangle on the CPU’s corner and align it with the triangle on the socket.
    AMD Ryzen CPU golden triangle
  5. Once the CPU is in place, push the metal handle back into place.

With this done, try booting up your computer to see whether the processor will be detected.

Fix 3: Update BIOS

Unlike Intel, AMD used one platform (AM4) to support several generations of Ryzen processors. However, to make this possible, the motherboard needs to have the appropriate BIOS to detect newer or older CPUs.

Fortunately, some motherboards have BIOS Flashback, which allows the BIOS to be updated through USB without a CPU installed.

With BIOS Flashback

If your motherboard does support such a feature, you’ll need another computer, and then here’s what you will need to do:

  1. Go to the motherboard’s official support site and download the right BIOS files (the version that supports your CPU).
    downloading BIOS files
  2. After downloading the file, grab an empty USB flash drive and format it into FAT32. You can do that by heading into This PC, right-click the USB, select format, and then under file system, select FAT32.
    formatting USB flash drive into FAT32
  3. Now extract the files you downloaded and add them to the USB Flash drive.
    extracting downloaded files
  4. Add the USB into the PC’s USB Flashback port (it should be marked).
  5. Ensure the PC is shut down, and then hold the BIOS Flashback button for about three seconds.

After a few minutes, the BIOS update should be finished, so boot up the PC and check if the CPU is detected.

Without BIOS Flashback

For the people without the BIOS Flashback feature on their motherboard, it’s going to be a bit more complicated.

You will need to find an older processor that the motherboard supports to access the BIOS. For example, if you want to use a Ryzen 3000 series CPU on a B450 motherboard that doesn’t have the latest BIOS, you’ll need to add a Ryzen 1000 or 2000 CPU into its socket.

After that, you can flash the BIOS to the appropriate version.

Fix 4: Replace The CPU

If the CPU or motherboard socket pins have been bent or damaged, you won’t be able to boot your PC. In that case, you could try fixing the bent pins by yourself, which is a daunting task. Or, replace the CPU (or motherboard) altogether.

This replacement can be costly, but it is also possible that it is covered by warranty if you didn’t damage the CPU yourself.

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Branko Gapo
Branko Gapo

Keeping up with the incredibly fast evolution of computer technology is almost impossible. That's why Branko will be using his knowledge on this matter to share news and information on all the latest essential technological innovations and advancements related to CPUs.