Multiple PSU power distribution calculations. 7x1070. Z270

Hi guys,

I'm stuck with PSUs while bringing my first rig to life. Begging for help.
I try to reimplement this build by nicahash, but with GTX 1070.

Now I have
- 1x Asus PRIME Z270-A. Up to 7 cards through risers + 1 by M.2 slot. Overall 8 cards max.
- 1x Intel Pentium G4560
7x Palit GeForce GTX 1070 GameRock [NE51070T15P2-1041G]. Samsung memory, good to overclock. One 8-pin connector on each card.

To power this I need about 2 kW PSU to feel safe (am I right?).

Obviously, I will never find such PSU, so I have to make multiPSU build.
So, my question is - how to distribute PSUs power between hardware?

E.g. I have 2 PSU - master and slave.
I figured out that it is mandatory to power motherboard and risers with a single PSU, so
-master powers up motherboard + risers + several cards with 8-pin.
-slave feeds all the other cards through 8-pin.

It is clear that one 8-pin is taking 150W max, how much should I provide for motherboard and risers?

Thanks!

You can assume that motherboard with CPU and SSD consumes 150W, if you will not run anything except miner. In this case CPU will be almost idle.
Regarding GPU consumption, it is little bit tricky.
GPU consume around 150-175W, but it takes 100W through 6- or 8- pins socket, and 40-50W through power connector on riser.
All digits above are approximate, of cause. But you can see proportions.

I have rig with mix of 480 and 570 on two PSU.
PSU1 (850W) provides power for MB+Celeron+SSD+8GB and 3 GPU (risers+main connector).
PSU2 (750W) provides power 4 GPU (risers+main connector).
PSU's are connected by "Dual-PSU ATX adapter".
Works just fine.

For you configuration, you can take 2*850W (at least "80 plus Gold"). If we assume that GPU consumes 175W.
But better option to take two 1kW PSU.
Usually, stronger PSU are equipped with better (thicker) wires. This is really important in case of 4 GPU on one PSU. I mean that you should never connect 4 risers on same PSU's wire with SATA. Not more that two risers on single wire. Perfect option to have separate line to each riser.
Don't forget to check wires after first 30 minutes of work (on very first start), if wires are hot - you have problem with possibility of overheating of wires and connectors. If wires are hot you should split risers. And if you have chip (low power) PSU, you can find that you have no more wires from PSU. That's why it's always better to have PSU with more power. It will be not hot and it will have more wires for risers.

Hey i'm also considering building that 8 GPU rig with A270 based on the nicehash one.

What i'm wondering about is if it will work with 8 times 8gb cards...

And maybe you'd need more system RAM for a setup like this, so 16 instead of 8 GB ? Not sure how much data is being passed around with mining...

Concerning the PSU...

i'm thinking about either a 1500 watt one, the Corsair AX1500i which has 80 PLUS certification with 94% efficiency rating.

Not sure if that would be enough. If you calculate 150 watt x 8 plus 250 watt for system = 1450 watt. Maybe a bit low margin.

Other option are the Antec high current pro's. they go from 750 to 1300 watt and you can link two of them (from 850watt and up), so they start together. (OC Link)

So with those you can have 2x850w = 1700w for a bit more room. or 850w + 1000w or 2x1000w and so on... You can even power 8 1080's with these !

haven't realy thought about how to lay out the connections yet.

@rush thanks, I'm trying to get a pair of Corsair RM1000x. Or Corsair for secondary PSU as it has 8 PCI-E cables and Zalman ZM1000-ARX for primary. Zalman has 8 molex connectors, I guess it can power up all risers.

@free I took a look, Antecs are quite expensive gears, but OC Link seems interesting. Could you please tell me why you think 8*8gb is a problem for RAM? I'm not fully into zcash algo, but I think (from the general noobie point of view) that as zcash can be well mined with 4, even 3 Gb GPUs (and less) - so even 4GB of system RAM won't be the bottleneck.

Maybe buy RM1000i instead. It cost 10$ more and you can monitor your power usage with a program on your PC.