How to Test Motherboard Without CPU?

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There are many reasons why you would want to test your motherboard without the CPU attached. Essentially, this test would allow you to troubleshoot your motherboard and point to where a certain fault lies.

Testing a motherboard without a CPU is quite simple. You have to make sure that it is connected to the power supply unit and is placed on a safe material. You CAN have the rest of peripherals and components such as RAM and hard disk attached if you wish, but you don’t have to.

You may also have to learn how to jump start your motherboard in the absence of a Power ON switch.

Basically, in the end you should expect to hear beeping sounds or LED flashes from your motherboard.

Below we will talk in detail about how to test motherboard without CPU and also touch base on how to troubleshoot the issues.

Why and Should You Test Your Motherboard without CPU?

There is nothing wrong with testing your motherboard without the CPU, the only thing you have to keep in mind is that the your PC will NOT pass the POST ( Power-On-Self-Test).

You will see nothing displayed on your screen as well because the motherboard does not have an onboard graphics processing unit. If you have a dedicated GPU installed in the PCIe, that too wouldn’t work without the CPU.

The only thing that you may observe are beeping sounds, if your motherboard has a beep code speaker, and LED flashes.

Testing if the Motherboard is Dead or Alive

On many occasions it becomes necessary to test if the motherboard is dead or alive.

Imagine you are building your computer and you have just purchased a new motherboard. If there’s a fault in it and if it came DOA (dead on arrival), it may become more problematic to identify the root cause AFTER you are done building your computer.

Hence, many desktop PC builders and gamers prefer to test their new motherboards BEFORE installing the CPU. This is often called the Pre-build bench test.

This is because as motherboards are sensitive components of the computer, they are prone to damage especially due to mishandling from shipping. There also can be a factory error to provide a non-functional motherboard.

This test may also become necessary if your PC has suddenly stopped working. You may want to perform this test to check if your motherboard is working properly.

Also Read:

How to Test Motherboard without CPU?

motherboard without CPU

Here is how you can test the motherboard without a CPU.

1. Unbox For Bench Testing

Bench test is when you test the PC components outside of the case.

First, unbox your motherboard. Next, remove it and set it on an anti-static foam or material found inside the packaging or on large piece of cardboard. You can even just place the motherboard on the box that it came with.

Do NOT place the motherboard on a bare metallic or conductive surface! Motherboards have a lot of solder points on the bottom. You do not want these points to come in contact with a metallic surface when turned on.

This is the reason why motherboards inside the case sit on standoffs. These lift the motherboard off from the CPU case so that it does not come in contact with the conductive material.

motherboard standoff
Brass Standoffs go into the case and hold the motherboard off from the metallic case surface.

2. Plug in the Power Connectors

You will need to attach 2 power connectors

  • 8 Pin for the CPU power connector on the motherboard
  • 24 Pin for the motherboard power connector
how to test motherboard without CPU 1
Location of the connectors

The layout of your motherboard may differ, but this generally the location of where you can find the motherboard and the CPU power connectors.

how to test motherboard without cpu 2
24 and 8 pin power connectors

Both the 24 Pin and the 8 Pin cables are provided by the Power Supply Unit.

how to test motherboard without cpu 3
Connectors from the PSU attached to the motherboard

Note that my Power Supply Unit also came with a spare 4 pin CPU connector for older motherboards and systems.

These days almost all motherboards come with an 8 pin CPU power connector. The 8 pin provides about 280 watts of power to the CPU, while the 4 pin connector only delivers half as much at about 140 watts.

In the very rare instance that you have a very old system, you would use the 4 pin connector.

3. Installing Other Components (Optional)

You can have the rest of the components such as RAM, hard disks and the graphics card installed if you wish, however, they won’t be of much use here without the CPU.

So whether you have them on or not would not make a difference. Although I would recommend that you at least have the hard disks unattached to save you from the risk of losing data due to any mishap.

4. Connect PSU to the Wall Socket

Go ahead and connect the Power Supply Unit to the wall socket. Make sure the power supply unit is also placed on a non conductive surface and make sure that you are grounded.

It would also be best to wear plastic slippers/shoes and to wear non-conductive electric gloves.

5. Turn the Motherboard On

If Motherboard is INSIDE the Case:

If your motherboard is inside the case then turning on your motherboard is quite easy.

Basically, you need to find the Power Switch Pins on your motherboard. These are often located on the Front Panel Header.

Then you can connect the Power Switch Cable from your Case to these Pins.

You may have to refer to the your motherboards manual to find out the information regarding the exact location of the Power On Switch pins.

The following shows the Power On Switch pins’ location for my motherboard:

power swtich front panel header

Motherboard-manual-power-switch w
Location of Power Switch Pins on Gigabyte GA-P67A-UD3
power switch connector
Power Switch Jumper from the CASE goes into the motherboard Power Switch Pins

Once everything is connected, hit the on button on the Case, and you should be good to go.

Also Read:

If Motherboard is OUTSIDE the Case:

Many newer and higher end motherboards have a manual turn on power button located on them. However, if you have an older or a budget motherboard, then you will have to manually turn the motherboard on.

There are two ways you can go about this:

  1. Using the Case Power On Switch cables
  2. Manually jump start the motherboard
Using the Case Power On Switch Cables

This is similar to the process we highlighted above.

Here, you will need to keep your CPU Case close to the motherboard so that the POWER ON SWITCH cables from the Case can reach the pins on the motherboard. Then you can go ahead and simply press the turn on button on the case as you would normally.

Manually Jump Starting the Motherboard

The second option is to manually jump start the motherboard. You will need a screw driver for this.

Basically you take the screw driver and with it touch the 2 Power Switch pins on the Front Panel Header.

jump start motherboard
Use a small precise screw driver to jump the pins of the Power On Switch

It would be wise to make sure that the screw drive does not touch any other pins here. Hence it is advisable to use a precision or a small flat screw driver.

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What To Expect? – Beeping Sounds and Flashing LEDs

If you test motherboard without CPU, then the first outcome to expect is that NOTHING will be displayed on your screen.

The other two outcomes to expect is that your motherboard will perhaps flash LEDs, make beeping sounds or both, or even nothing at all.

These are essentially codes indicating where the problem lies.

Beeping Sound Codes

If your motherboard does have a speaker, it will make beeping sounds codes to indicate the issue.

The amount of beeps it makes basically would tell your where the problem lies.

For instance:

  • 1 Beep – issues with the memory
  • 2 Beeps – issues with the motherboard
  • 5 Beeps – issues with the CPU

There is a whole list of beep sound codes. You can learn more about them here. If you start the motherboard without a CPU but with RAM and other other components installed, you may potentially hear a 5 beep sound code.

If your motherboard DOES not have a built in beep code speaker, then you can invest in a very cheap one and install it yourself.

motherboard speaker
A beep code speaker that you can buy
beep code speaker w front panel header
Pins where you would install the beep code speaker

LED Flashes

motherboard flashing leds
Your motherboard may flash LEDs to indicate what is wrong with it.

You may also see certain LEDs on your motherboard flash indicating where the problem lies. To understand this further, you may have to refer to your motherboard’s manual.

Also Read: How to Reset Motherboard?

No Beep Sounds & No LED Light Flash

The final outcome that you may see is literally nothing.

If you hear no beep sounds and no LED flash lights, then do not fret. This still does not indicate that your motherboard is damaged.

Motherboards Without LED or Speaker

Some motherboard do not come with either of the two i.e beep sound code speaker and the LED lights for indicating where the problem lies.

In this situation, I would advice testing the motherboard through fans. There are two ways you can go about this:

  1. Connect the Cooler Fan to the CPU_FAN header.
  2. OR connect the Case Fans to the 3 Pin FAN headers located on the motherboard which are often labelled as SYS_FAN (Note not all motherboard have FAN headers).

In the second method, you are essentially powering the Case Fans through the motherboard instead of the Power Supply Unit. You will obviously need a Case FAN that has the three Pin connector

case fans
Case Fan with three pin connector

If the CPU or System Fans turn on, then you can be certain that the motherboard is receiving the power. This can POTENTIALLY indicate that the motherboard is OKAY, unless, of course, if an essential IC or controller is damaged. In that case the motherboard will still be receiving the power but may not start.

In the end if you have made sure that the motherboard is receiving the power, the last thing to do is to actually attach the CPU and test your system.

Also Read:

Conclusion

In this article, we talked in depth about how to test motherboard without CPU. This is an essential step for many PC builders who want to test the components before installing them into the Case.

This test would highlight if and where the problem lies. Testing the motherboard without CPU is a great way of checking if the motherboard is alive or dead particularly when its brand new and you want to check if it came DOA (dead on arrival).

While we reiterate that the procedure is fairly safe, we advise that you exercise caution especially if you are a PC builder or seeking to be one. This is because any mishandling or error on your side can also damage the motherboard.

Also, when in doubt, it is best to refer to an expert technician instead of fiddling around with the delicate components yourself.

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Author:

Atif Qazi
Atif Qazi is the founder of PCGuide101. He is a digital nomad who loves everything PC. He is a PC builder, tech enthusiast, engineer, and a lover of single player lore-rich RPG games.

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