PC switched off abruptly ASUS M3A78-EM with AMD 9950 Black Edition

I have ASUS M3A78-EM with AMD 9950 Black Edition & 2 x Transcend 2Gb 800 Mhz RAM &
cooler master 600W SMPS.
Whenever I turn ON my PC.It runs for 5-90 seconds & then gets switched off abruptly.
Same problem i faced around 1 month ago so i replaced my CPU.
Currently i am running new CPU from last week.It rans smoothly for week.now same problem again.
I tried RAM into diff slost but stil same.
I removed RAM & HDD and started PC again but still problem persists.
Currently CPU temp is shown as 44 C & sys temp is 30 C in BIOS
let me know problem is with CPU or MOBO or SMPS.

Try other PSU,RAM on ur system ...

Can u update BIOS of mobo ???

Do you get a Bsod than it shut's off. Or just shut's off i think you should check the Psu if it is ok than most probably the mobo.

I'm pretty sure it's the power supply. I ran the same mobo and CPU with a VX450 for 6 months pretty much 24x7, and nothing happened. The same mobo carried a X2 550 and recently a X4 620, and it runs just fine.

I did however put some extra sinks on the MOSFETs just to be sure, the 9950 is on the edge of the board's capabilities. Both the M3N and the M3A overclock the CPU to 3GHz quite easily too, so I would suspect the power supply first.

updating BIOS or increasing voltages will it helps...

I'm 99% sure you are using a CM Extreme series PSU. Extreme series has high failure rates. Change your PSU to Gigabyte Superb 460W which would cost 2.2K if you don't have any GPU. If you have one or plan to have one, you may have to get something better than that.

anyone will easily attracted to ASUS M3A78-EM for it's price. try to look at the bios update history.(i cannot post you the link because of the quality of web service asus offered to us)
actually it is a totally faulty motherboard. it's price should be -5000/-.

just update the bios and ready for another problem.
watch for another bios update in next 1-2 months and again update.
update will continue up to end of life of ASUS M3A78-EM.

update bios ,check psu ,Ram
and check HDD connections

I too have the same problem and strangely, it is even more frequent during winters. Needs the warmth, I guess, but jokes apart, it is to do with the PSU. I changes to a VX450 and it worked flawlessly. Also check the cables connecting your cabinet’s power button to the MoBo.

It's definitely the problem with PSU...I also faced similar problem...