Sabertooth 990fx, able to POST but crashes!

[Dem]

Okay so, having some major problems with my Sabertooth 990fx, it started last week when my PC was just completely shutting down even while idling, thought it was PSU problem. Tried with new PSU and my crashes still occur, it's crashes now after about 15 seconds after boot up, but I am able to POST and get into BIOS and change some things but I have to be fast about it. I've done multiple CMOS resets by jumper and battery, it helps a little but still crashes. Yesterday I was playing games all day but I woke up to it shut down and now it just shuts down quite quickly even after a reset. RAM checked out okay and so did CPU and everything else, I haven't tried breadboarding and I don't have a mobo speaker but I do get red LEDs on the mobo before shutting down which don't really help.

I already ordered a new mobo but I'd like to understand the problem of the crashes, if it boots up and gets passed POST and I can get into BIOS, what could be the problem? There hasn't been any new hardware changes and the crashes seemed to come from nowhere, I was running my AMD 8350 overclocked at 4.5Ghz with temps no greater than about 50c and never experienced instability at these speeds with my voltage at v1.5. What happened?

Specs:
Motherboard: Sabertooth 990fx
CPU: AMD 8350
RAM: 8GB DDR3 Corsair Vengeance
GPU: MSI GTX 770
PSU: Corsair Enthusiast 650w
SSD/HDD: Samsung SSD, Seagate SSHD, WD Black HDD
Case: Antec 900

[Geek-9pm]

OK. You already did the things that would have been offered here.
What you need to know.
Beth  the mobo and the PSU are designed to shut down when thee is a sensor that reports a problem.
The most common issue is over heating when a fan stops.
The other most common is over current from a bad electrolytic capacitor.
After those two,  almost anything.
Where do you live? Are power drops common in your area?
Do you run your PC on  120 or 240 volts?
Is your PC connected to a wired network? Dial-up?
Do you have scanners or printer connected when  the failure comes?

[Dem]

I don't have power outages here and no other devices are connected, PC is on normal volts whatever it is for USA. No signs of failed capacitor. Would a bad bios cause it to shut down? I'm thinking maybe of buying a new bios chip and replacing it. Idk what else I could try.

[Geek-9pm]

Please provide make and model of your computer.
Or model of motherboard and CPU.
Some new motherboards do not have BIOS on a replaceable chip.

AS for unpredictable shut downs, here is a scenario.
A common failure is when somebody ttys to upgrade the CPU with a fester chip. But the chip set does not really support the faster CPU. But without details, there is no way of knowing that is what happened in  your case.

[Dem]

It's a Sabertooth 990fx motherboard and AMD 8350, it's "military grade" motherboard and meant to handle extreme overclocking. Well I will see if it works with new motherboard.

[DaveLembke]

Just wondering of the CPU FAN is spinning properly as for if the tach is not reporting movement to the motherboards built in melt down protection circuit, it will shut down to protect itself. If your bios shows fan speed info, I would check as fast as you can to see if it shows the rpms of the CPU fan as for if the CPU FAN is defective and not reporting its speed, the system will shut down exactly as you described.

Sometimes this is caused by failing to plug in the CPU FAN into the jack on the motherboard labelled CPU FAN which is a critical system sense connection for system fan health.

I have seen where a person plugged the CPU FAN into the CASE FAN 3 pin jack on the motherboard and left the CPU FAN 3 pin not plugged into a fan and it causes this same issue. The CPU FAN jack is critical to a operational computer... some systems allow it disabled, but most do not.

[Dem]

Yes I am aware of the CPU FAN connector, I have a liquid cooling radiator, the Corsair H55 with 2 Corsair High Performance Fans in Push/Pull, and the heat distributor is plugged into the primary CPU FAN connection. All fans run everything runs, I boot up fine but shuts downs eventually (in a small time frame). Like I said nothing has changed these past few months, these crashes came out of nowhere, I am out of ideas as to what the problem is. I read on other forums that a few others with the same board have had the same problem, but no fixes.