tuaha khalid

I have a sff hp 800 g1 prebuild with 220/240 watt power supply I have connected the gpu directly to the motherboard it will provide 75 watts to it but i know it isn't enough i have a 420 watt atx power supply lying around. So i want to know that should i connect that one or buy a 150 watt as rx 480 uses 185 watts?

I have a XFX rx480 which i want to power externally it has a 1x8 pin what rating should be of the external psu to give it enough power?

Thanks for the help?

I have i5 4570 and my gpu is rx 480 8gb should i upgrage to i5 4690 or i7 4770

Now i have also connected my gpu directly to the motherboard to test wether the pcie extension cable is causing the problem but still problem remains

Yes tried another vga cable

Yes I have checked my gpu in my friends pc without pcie extention it worked fine He gamed for more than 4 hours

I have a sff desktop Hp 800G1 Spec: i5 4570 ,8gb of ram , 1tb hardI have connected an external gpu XFX RX480 8GB using an external power supply and pcie extention cable Now the problem is when i start gaming all things work fine but suddenly after some time 20-30min later display turn black saying no signal going to power saving mode this same happens every timeI dont know whats the problem and which part is causing it