I recently upgraded to a dual power supply setup which had me researching on how to connect them safely.
I came across posts suggesting powering the riser and PCI-E power connector on the card with the same PSU. Others say the psu that powers the motherboard must also power alll the risers. The slave psu should only power the PCI-E power connector on the card.
https://bitcointalk.org/index.php?topic=1761303.msg17825999#msg17825999
https://bitcointalk.org/index.php?topic=1843586.msg18351224#msg18351224
Ultimately, I did follow the latter suggestion as it seems logical the same power supply that powers the motherboard should also power the risers connected to the PCI-E slots on the motherboard. The second slave power supply only powers the 6 & 8 pin auxiliary power connector on the video cards. According to another post I came across that connecting the PSU's that way ensures they share the same ground, which is important.
https://bitcointalk.org/index.php?topic=443540.msg4878774#msg4878774
I researched for a single 12V rail, dual conversion PSU to use as suggested and went with the EVGA SuperNOVA 850 G2 220-G2-0850-XR 80+ GOLD 850W for $110 after rebate from Newegg:
https://www.newegg.com/Product/Product.aspx?Item=N82E16817438018
It's a dual conversion, single 12V rail PSU. It has 4 PCI-E 8-pin slots, 4 6+2-pin PCI-E cables and two of the cables also have a 6-pin PCI-E splitter cable. They alaso have a 750W model.
To connect the two PSU I went with the Add2PSU unit, but it's just a relay to daisy chains the PSU's so they start at the same time. The same can be done by jump starting the PSU with a piece of thin metal between the green wire and a black wire on the slave PSU and then turning on the switch on the back before starting the computer.
https://forum.overclock3d.net/showpost.php?s=3c0b5ead1c29a7c47c0e8fceb274ecf8&p=3815&postcount=1
Or using an automotive relay:
http://www.jonnyguru.com/modules.php?name=NDArticles&op=Story&ndar_id=27
You could also connect the two green wires on the PSU's and they will both start at the same time as long as they share the same ground.
I came across posts suggesting powering the riser and PCI-E power connector on the card with the same PSU. Others say the psu that powers the motherboard must also power alll the risers. The slave psu should only power the PCI-E power connector on the card.
https://bitcointalk.org/index.php?topic=1761303.msg17825999#msg17825999
https://bitcointalk.org/index.php?topic=1843586.msg18351224#msg18351224
Ultimately, I did follow the latter suggestion as it seems logical the same power supply that powers the motherboard should also power the risers connected to the PCI-E slots on the motherboard. The second slave power supply only powers the 6 & 8 pin auxiliary power connector on the video cards. According to another post I came across that connecting the PSU's that way ensures they share the same ground, which is important.
https://bitcointalk.org/index.php?topic=443540.msg4878774#msg4878774
I researched for a single 12V rail, dual conversion PSU to use as suggested and went with the EVGA SuperNOVA 850 G2 220-G2-0850-XR 80+ GOLD 850W for $110 after rebate from Newegg:
https://www.newegg.com/Product/Product.aspx?Item=N82E16817438018
It's a dual conversion, single 12V rail PSU. It has 4 PCI-E 8-pin slots, 4 6+2-pin PCI-E cables and two of the cables also have a 6-pin PCI-E splitter cable. They alaso have a 750W model.
To connect the two PSU I went with the Add2PSU unit, but it's just a relay to daisy chains the PSU's so they start at the same time. The same can be done by jump starting the PSU with a piece of thin metal between the green wire and a black wire on the slave PSU and then turning on the switch on the back before starting the computer.
https://forum.overclock3d.net/showpost.php?s=3c0b5ead1c29a7c47c0e8fceb274ecf8&p=3815&postcount=1
Or using an automotive relay:
http://www.jonnyguru.com/modules.php?name=NDArticles&op=Story&ndar_id=27
You could also connect the two green wires on the PSU's and they will both start at the same time as long as they share the same ground.
Dont know why you people make it so complicated.
http://www.parallelminer.com/product/hp-1200-watt-power-supply-kit-for-gpu-mining-platinum-94-zec-dash-eth/
Power the PCI-E power connectors this way, hell you can even power the risers with it, it doesn't matter from my testing because the hot of one plug doesnt run into the neutral of another plug. Just turn on the PCI-E/riser power before you turn the mobo power on. It doesnt even matter if you switch them on and keep the mobo off, the GPU gets idle power but generally this is never enough power to even require the fans to turn on (passive cooling will keep the chip below 40).