HelloWhen i turn on my computer without 4 pin ATX +12 volt power cable my computer starts and everything goes fine but when i connect it to my motherboard my computer does not start.i want to know that is this cables necessary for normal computer operation or i can go without it??I am using ATX 20+4 pin main power cable for my motherboard power.
As far as i know you need both connected. you might have updated your bios that's why your four pin isn't working. Do check the power configurations in your bios. I am definitely sure that's where the problem is. Hope that helps.
The problem is with your SMPS (as much I know about computers). SMPS is Switched Mode Power Supply. It is the thing which supplies different power to different components of a computer. If your computer is not getting any power supply, that simply means your SMPS fails to draw current for your devices. You should either repair it or get a new one....
The 4-pin 12V ATX connector (yellow and black wires) supplies voltage to the Voltage Regulator MOSFETS that power the processor. If not connected, processor does not power up at all. If it is connected and PC does not start, power supply is sensing an overload/short on the VRM circuit, thus enabling PSU overload protection to protect PSU and motherboard as well. I am suspecting that either motherboard (at VRM portion) is grounded to PC case or the cooler is touching a circuit of the VRM. Try remounting motherboard and/or cooler.
