I was given an HP Z420 workstation for free and was hoping to make it into a second gaming workstation since I have a spare Geforce GTX1060. The downside is I noticed the Z420's power supply only has two 6 pin PCI-E power connectors and not the single 8 pin I need for the card. It's a 600 Watt power supply so it's pretty beefy but would a 6 pin to 8 pin converter really work? It would be nice to just get a converter and not buy a new power supply for it especially as I would have to do some customizing to make it fit properly.
Check your 6 pin connectors for three yellow wires. If it does, it is safe to use a 6 to 8 pin converter. The three holes on opposite side of the retention clip would be the 12v lines. Technically the middle hole could be not filled. Always is though.
Just check how much power is allowed on the 12v rail(s). There should be a sticker on side of power supply. While you have a 600 Watt, it may be a weird one that has a ton of that 600W for the 3v/5v rails for a storage heavy workstation instead of majority for 12v rail(s). So add your CPU + GPU power usage and make sure its under that number. However, the GTX 1060 power usage should be well within not even bothering to check.
It's been a while since i created my own power cables(never had to replace them so far ¯\_(ツ)_/¯), but ask if you have questions.