Problem with CPU, PSU or MoBo. Help please?


I'm not sure which action to take, so please read this series of events and let me know what you think.

Here is my PC specs:

Hard Drive: Seagate Barracuda 7200.7 ST3160023AS 160GB 7200 RPM
Processor : AMD Phenom II X4 940 Deneb 3.0GHz Socket AM2+ 125W Quad-Core Black Edition
Video Card: BFG Tech BFGR88640GTSOC2E GeForce 8800 GTS 640MB 320-bit GDDR3 PCI Express x16
Ram: CORSAIR XMS2 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 675 (PC2 5400) Dual Channel
MOBO: ASUS M3A79-T Deluxe AM2+/AM2 AMD 790FX ATX AMD Motherboard

I have just installed a new CPU in m y computer. Previously I was using AMD Athlon 64 X2 6000+ Windsor 3.0GHz Socket AM2 processor. My old processor was over heating and giving me issues after I reinstalled it on a new mobo (the one listed above). I would get shut down, freeze mid game or get other errors. A lot of the time it would reboot and I would get a CPU overheating error.

So I replaced the CPU with a new AMD Phenom II X4 940 Deneb 3.0GHz Socket AM2+ quad core processor. The mobo its on is fairly new (ASUS M3A79-T Deluxe AM2+/AM2 AMD 790FX ATX AMD Motherboard). It was running fine for a few days after I changed the processor, but then out of no where the computer shut off.

Since then my computer will not stay on for more than a minute.

At that point I thought that the power supply died. Once it would shut down abruptly, I would not be able to turn it on again unless i switched the PSU off then on. Once it is restarted again it will turn off within 10-15 seconds.

After reading online I decided to test each component out on the computer using the PSU. Apparently if I plug the 20+4pin connector into the mobo all of the components plugged in will power up. Once I Plug the 8 pin EPS connector into the EPS elot on the mobo, the problem happens again. Shut down within a few seconds.

Once that didnt work I decided to take my MOBO battery out so the mobo would power down. I replaced the battery and ultimately the same problem happened. Shut down 10 secs.

I took out a crappy 500 watt PSU that I had lying around and tried my best to hook it up. There was only a 4 pin connector for the EPS even though my mobo has a 8 pin slot. I plugged in the 4 pin in the 8 pin slot and plugged in the 20+4 pin in the slot. The computer will now turn on, but will not find the hard drive or cd drive. I can load the bios menu but it is extremely slow. As if no other components of the computer are loaded besides the mobo.

Any ideas? I'm out of things to try and patience is running low. Please help.
4 answers Last reply
More about problem mobo please
  1. Sounds like your first problem is your PSU. The fact that the pc runs for a few seconds sounds like the PC doesnt have enough power.

    Newer CPU's require more power than older single core chips hence the 8 pin slot. Im guessing by using the older connector your pc is being starved of power.

    Best bet is to replace the CPU with a newer one and see if it cures your problems - if you dont want to fork out the cash for the PSU you could buy a PSU tester.
  2. thanks. I assumed it would be the psu. Ill check if I still have the warranty on the psu. if not what do you think i should buy?
  3. Seasonic, Corsair, and PC Power & Cooling are all high quality psu's that earn high marks in technical reviews and comparisons. They are very reliable and stable. They're also the brands most often recommended by veterans at this forum.
  4. ^+1 for the brands listed.
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