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Mobo won't boot after cpu upgrade

Last response: in CPUs
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February 26, 2009 7:22:59 AM

I have an asus p5b mobo... today i replaced the psu (to an Antec 500w Earthwatts) and the cpu (to a q9650). According to the Asus website the p5b board is compatible with the q9650. Before installing the new cpu I did update the bios successfully. So I hooked everything up, plugged the power cord into the psu and then hit the power button.... nothing, silence. The green LED on the mobo is on so I assume it's getting power. I cleared the CMOS by removing the battery and by moving/moving back the RTC/CMOS jumper. I hit the power button... nothing. I remove all of my RAM except 1 stick... hit the power button... nothing.

Then I install the old cpu and old psu and go through all of the same steps and.... nothing, even though the system was working perfectly earlier today.

What could be the problem? I assume that just because the green LED is on that doesn't mean the mobo is in 'perfect' working order? Are there any other possibilities? Anything else I should try?

Thanks.

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February 26, 2009 8:13:55 AM

try jump starting it using the 2 pins on the mobo that connect to the power switch?
February 26, 2009 8:19:42 AM

calpolyarc said:
I have an asus p5b mobo... today i replaced the psu (to an Antec 500w Earthwatts) and the cpu (to a q9650). According to the Asus website the p5b board is compatible with the q9650. Before installing the new cpu I did update the bios successfully. So I hooked everything up, plugged the power cord into the psu and then hit the power button.... nothing, silence. The green LED on the mobo is on so I assume it's getting power. I cleared the CMOS by removing the battery and by moving/moving back the RTC/CMOS jumper. I hit the power button... nothing. I remove all of my RAM except 1 stick... hit the power button... nothing.

Then I install the old cpu and old psu and go through all of the same steps and.... nothing, even though the system was working perfectly earlier today.

What could be the problem? I assume that just because the green LED is on that doesn't mean the mobo is in 'perfect' working order? Are there any other possibilities? Anything else I should try?

Thanks.


I had the same problem when upgrading the cpu,
are you using bios 1238?,
do you get any beep codes?
why a green led mine is red/purple?
If you are not getting any beeps it sounds like the cpu is not installed correctly
does cpu fan start?
did you connect the extra cpu power supply
try pressing the computer reset button a couple times
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February 26, 2009 4:50:48 PM

The bios update was necessary to support the new cpu and the computer worked fine after the bios update with the old processor.

I'm not getting any beep codes or fans starting, literally NOTHING happens when I press the power button.

I'm using bios 2001.

I'm going to try jump starting it.
February 26, 2009 5:38:39 PM

jump starting didn't work... I can hear a 'click' in the psu telling me that I've made the jumpstart connection but as I hold it there nothing else happens. And this is with the mobo out of the case and only the essentials connected: 4 pin power, 24 pin power, fan power, cpu, fan, video card, 1 stick of ram.
February 26, 2009 5:48:33 PM

CPU fan plugged in, HSF seated right, CPU seated correctly, did you remove the motherboard at all? Just wonderin' :) 
February 26, 2009 5:49:06 PM

Have you tested the system with the old cpu and psu? There's a chance that the new psu is doa.
February 26, 2009 6:06:22 PM

Yes, what I stated above about the jump starting not working is with using the old cpu and psu :-/
February 26, 2009 6:52:03 PM

I think you missed a connection. ie: ATX 12v maybe?
February 26, 2009 7:38:45 PM

Bent pins in the CPU socket maybe?
February 27, 2009 3:59:41 AM

I'm ashamed to even say what the problem was but I will just in case it helps someone in the future...

I had the floppy drive power cable from the PSU plugged into the 'power fan' pins on the mobo :heink:  For some reason I had it stuck in my head that the psu needed to supply power separately to the fan. :pfff: 

Quote:
And this is with the mobo out of the case and only the essentials connected: 4 pin power, 24 pin power, fan power, cpu, fan, video card, 1 stick of ram.

See where it says 'fan power' and also 'fan'... yeah that's the problem, lol. If only I had a floppy drive that cable would've been spoken for!

:fou:  .... deep breath, time to move on...

Thanks everyone for your time and suggestions.
!