Underclocking AMD FX 8120 CPU

[QARTS]

Hello,
So my current PC specs are
AMD FX 8120 Stock
MSI 970A G46
Hyperx fury 8GB 1866
WD 4TB
CM Hyper212X
MSI GTX 750Ti
XPro 550W PSU

I've bought a GTX 780 GPU and after installing it in my PC(Swapped my 750Ti) and started a game suddenly my PC switched off automatically.
I bet its the heating issues,so am thinking of Underclocking my 8120.
IS this a good solution?
My case is well ventilated and good air flow too.
PSU has 2*8Pins and 1 6pin connector.
PS-If you suggest underclocking then please suggest me the optimum freq at which my PC will be stable.
Thanks all.

Edit

Also what if i disable 2cores from msconfig/BIOS?
Will this add to reduce the temps even more.
PS-I wont bother losing bit of performance though my prime concern is heating issues.

 

[sourodip]

Have you tried re-applying Thermal Paste on your 8120? Does the same happens while playing on the 750Ti?
What games are you playing? Does it crash while playing all games? What are temps before crashing?
A 780 requires a minimum of 600W PSU and your PSU is not at all recommended. Change the PSU.

 

[QARTS]

With the 750TI everything was fine played BF 1 with it without any errors!!
With the 780 no matter which game i start-FC 4,BF 1 the problem occurs everytime.
IF incase the game starts then after a couple of minutes it Switches off.
I cant afford to change the PSU as for now thus thought of Underclocking and disabling 2 cores.

 

[sourodip]

No, that won't work. Downclocking won't be that much of a help until and unless you are using a 750Ti instead of a gtx 780. You need to change your PSU ASAP if you want t ouse a gtx780. Otherwise change your GPU with the GTX 750Ti.

 

[QARTS]

Alright,so believe that changing the PSU is more convenient option for me
Can you suggest me a good PSU under 4-4.5k Indian Rupees?

 

[DSzymborski]

The best way to look for overheating is to actually look at the temperatures. That'll tell you right there if you have a heating problem.

My money's on the junky PSU. Sure, it has connectors, but I can wire an electrical outlet to a banana, but it doesn't mean I can plug in a TV and it'll work. It claims 31A combined for +12V rail, which is anemic for a supposed 500W, most likely this is a bad 300W power supply (it won't get the 14A and 17A maxed out on each connector). A 780 can get to 230W on load by itself.

Return this power supply to its natural habit: the local dump.

 

[Roland Of Gilead]

The best way to look for overheating is to actually look at the temperatures. That'll tell you right there if you have a heating problem.

My money's on the junky PSU. Sure, it has connectors, but I can wire an electrical outlet to a banana, but it doesn't mean I can plug in a TV and it'll work. It claims 31A combined for +12V rail, which is anemic for a supposed 500W, most likely this is a bad 300W power supply (it won't get the 14A and 17A maxed out on each connector). A 780 can get to 230W on load by itself.

Return this power supply to its natural habit: the local dump.

Class answer

 

[DSzymborski]

Unfortunately, prices of power supplies are horrible in India. Cheapest I can find a good power supply on India tech sites.

http://hardwire.in/power-supply-units/414-seasonic-s12ii-520-w-.html

In a pinch, you can go for an Antec VP, which is cheaper. I'm not a fan of this low-end implementation, but it's still far better than what you're currently trying to use, mediocre capacitors and all.