My video card works when two 6 pins are connected to it but fails when a 8 pin is used

cottoncandy

Reputable
Feb 14, 2016
4
0
4,510
I built a new pc yesterday using these parts
PSU: SeaSonic 650W
Case: NZXT H440
CPU: Intel Core i5-6600k
CPU Cooler: Cooler Master Hyper 212 EVO
GPU: MSI Radeon R9 390
RAM: G. Skill Ripjaws 8GB
HDD: Samsung 850 EVO-Series 250 GB

When I first booted up my PC I used the two 6+2 pins from the PSU but left of the +2 pins and connected it to the GPU. The GPU has a 8 pin slot and a 6 pin slot and I put 6 pins in both. The computer worked fine then (I was able to access the BIOS), then I decided to add the +2 pin to the 8 pin port on the GPU to provide more power. When I did this the video card ran fine, but there was no image on the screen. I am unsure why this is happening and why adding the 2 pins would cause such a change.
 

cottoncandy

Reputable
Feb 14, 2016
4
0
4,510
No I did it after I turned the PC off. When it didn't work I returned to the two 6-pin configuration and it worked again, so it seems that the video card is still functional