# Unknown CPU detected



## Sonali98 (Nov 21, 2008)

I have upgraded my pc with ASUS P5n72-T Premium motherboard and Intel (R) Core (TM) 2 CPU 3.00 GHz E8400 processor. When I boot the pc up I get the following error message:

"Unknown CPU detecetd BIOS Update is required to unleash its full power"

I can't go further than this. If I press F1 it brings me back to the error message. If I press DEL it takes me to BIOS update page.

OS on my pc is : Win XP Pro SP 2

Has anyone had similar problem? 
Can any one assist me in fixing this problem?
How do I update BIOS?

Thank you.


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## Tumbleweed36 (May 14, 2005)

Some boards require a bios update to support the latest CPU. Therefore, at times one has to get a slower CPU and flash the bios before you can use the newer one. I know, it is a PITA, but we see that quite often and I suspect this is where you are with this one.

If a friend or neighbor has an older CPU you can use to flash this bios, then give that a try before you put this one back in.


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## fer (Feb 22, 2009)

Sonali98 said:


> I have upgraded my pc with ASUS P5n72-T Premium motherboard and Intel (R) Core (TM) 2 CPU 3.00 GHz E8400 processor. When I boot the pc up I get the following error message:
> 
> "Unknown CPU detecetd BIOS Update is required to unleash its full power"
> 
> ...


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## Tumbleweed36 (May 14, 2005)

Before we get any further, clear the cmos and see if it recognizes the CPU for what it is. If that doesn't help, then we can move on to look at other things.

Here are instructions:

*Clearing The CMOS *


Clearing RTC (Real Time Clock) RAM: 



Turn OFF the computer and unplug the power cord.


Remove the onboard motherboard battery.


Move the Jumper Cap from pins 1 & 2 (default) to pins 2 & 3. Keep the cap on pins 2 & 3 for ten seconds, then move the cap back to pins 1 & 2.


Reinstall the Battery.


Plug in the power cord and turn on the computer.


Hold down the DEL key and enter the bios setup menu to re-enter data.

*Notes*: Some motherboards use different key combinations to enter the bios setup menu.

There are also some motherboards that you can simply push a button to achieve the same as moving the jumper from pins 1 & 2 to pins 2 & 3 and then moving the jumper back.

In addition, there are some boards that you simply use a screwdriver to short across the two jumper pins (no jumper), but this serves the same a removing the jumper and replacing it to adjacent pins.


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