You talking about the sense wire on a
PCIe connector?
If so, that's a ground wire that that tells the video card that it has an 8-pin connector plugged in..Without it detecting the extra sense wire on the 8-pin it would think a 6-pin connector is plugged in to an 8-pin socket (which will fit and sometimes work) and might cough up
this on the screen.
Get cables from Cablemod, they'll be fine..If you have any questions you can always contact them.