Quick answer please

have a sabertooth 990fx. It has an 8pin power connection on the board.but my PSU only has a six pin and four pin. The manual shows a pic of a four pin in the eight pin. Is that a good I idea to plug the 4 pin in only?

doesn´t your psu has 2x 4 pins?

Please post the model of your PSU as well.  With the power of the internet at our hands, we can tell you how to hook it up without an issue, we just need to know what it is.

This is a double poooooost. 

Its a rosewill 450 model number - cvp450is, I'm ordering another PSU. But I wanna try my new stuff out. That's why I'm trying with this PSU. Its my current psu

And no it doesn't have 2x4 pins

Thnx i allready deleted the second one ;-)

 

well you can run your computer with only one 4 pin connector. but its not something i personaly recommend to do. especialy if you run a FX8350 on it.

i would recommend to buy a new psu someday

Yeah I ordered a new one. But I'm excited. Hana. Well according to this PSU calc. I'll only use about 280 to 400w. My GPU is low end. I'm in the process of building a new PC. But I'm getting piece by piece.