I just purchased an ASUS Radeon HD 4890 1GB. I noticed that there are 2 power inputs on the card. I'm guessing that one is for backup power? The other is an 8 pin slot and an 8-pin to 2x 6 pin converter was included. Does this mean I need 2 dedicated rails to each 6-pin on the converter PLUS another 6 pin on the backup? Sorry if my vocab is a bit off.