Dead CPU(s)? Or Mobo? No POST or Beeps!!!

[Contrary]

Hello all, new to the forum and first post here.
I sure hope someone can help me!
Here's my problem... After putting my system together, i get no POST, no beeps, fans stay running and system stays powered on until i shut it off, clear CMOS same thing happens. I take my RAM out, no Beeps. I try a friend's PSU, same thing. Now here's something interesting. I swap in his CPU and clear CMOS, system just reboots every few seconds. I swap my CPU into his system and clear CMOS, also get the reboots. I swap his CPU back and his system works fine. I swap mine back and once again power stays on, no POST, no Beeps.
All was done with integrated graphics. There is no video showing at any point. My conclusion is that i have a dead CPU or a dead Mobo, Can someone please confirm which one it is?

Specs:
MOBO: MSI Z77A-G41.
CPU: Intel Core i5 3450 - Ivy Bridge, Friend's CPU is a 3550.
RAM: Patriot Viper 4GBx2 1600mhz.
PSU: Corsair CX500.
Stock cooler.

 

[patrickthefirst]

I had a no post situation before; I refitted the cpu and it started to work again so I would definitely say that the cpu is the main culprit; however I'm thinking the PSU might be also be suspect as I've had random reboots when my old PSU was dying. You havn't listed your wattage, maybe cross check that you have enough power?

I'm an amateur but thought I'd give my two cents. Good luck!

 

[Contrary]

I had a no post situation before; I refitted the cpu and it started to work again so I would definitely say that the cpu is the main culprit; however I'm thinking the PSU might be also be suspect as I've had random reboots when my old PSU was dying. You havn't listed your wattage, maybe cross check that you have enough power?

I'm an amateur but thought I'd give my two cents. Good luck!

During this process the CPU was removed and replaced several times, so i dont know. PSU is a CX500 (500w). I also forgot to mention that i tried my friend's Antec 650w with the same results.

 

[patrickthefirst]

As a precursor to any further help my two best questions would be. When do the restarts happen exactly with your friends cpu in, and can you enter your bios with his cpu in and look at all your stuff?

 

[Contrary]

As a precursor to any further help my two best questions would be. When do the restarts happen exactly with your friends cpu in, and can you enter your bios with his cpu in and look at all your stuff?

I turn the system on, it powers up for roughly 2-3 seconds, then shuts off. a few seconds later it turns back on for another 2-3 seconds, then shuts off yet again. This process keeps repeating until the PSU is shut off.
As mentioned above, i am getting no POST or video, so entering the BIOS is out of the question, and the restarts are too quick for that anyway.