Connecting GPU's with and w/o Risers

[Apostlekin$$$]

If you aren't using a motherboard that have enough space for up to 6 PCIe x16 slots it's better to buy risers to connect your graphic cards, I'm talking about motherboards like in the picture below, if this is what you own then you have no need to buy risers




With this motherboard I can fix up to 4 graphics card without need for risers as there will be good air flow between the cards

[mantonio333]

This might be a dumb question but...any issues connecting some GPU's directly on the motherboard and some using risers?

Most mining rigs I see in the internet either have all their gpu's connected on the motherboard or all via risers.

I'm planning to use Asus Z370-E for my rig.

You have to understand how a GPU is powered.
Some power come from the PCI-E slot (75W max on PCI-E 16x slot) and some power come from the 6/8 pins PCI-E connector(s) of the GPU.

The motherboard is compatible with SLI/Crossfire, so at least using 2 PCI-E slots directly is totally fine. Because it's design to give power simulteously to 2 GPU from the PCI-E slots.
If you want to use more GPU, you have to use powered risers (like USB risers) so the power draw that the GPU expect from the slot will not come through the motherboard (and it's a good thing, because it will not be able to safely provide so much power to 4-6 GPU on the slots).
The power will come from the risers with the molex or sata power cable directly from the PSU.

Do not use to much risers on 1 PSU cable.
For exemple, if you have 1 SATA cable from the PSU with 5 SATA plugs ... do not plug 5 risers, be cause it could stress this cable.
I prefer to have max 2 risers per cable on the PSU

Okay I see. I will have two separate 850w PSU's to power eight 3070. I'll make sure to distribute powering the risers between the two psu's. Thanks!

If you are planning to power 8x RTX3070 it will be wiser to buy power supplies with 1200watt capability because a single RTX3070 draws up to 117-120watts per gpu now do the math, that's 960 watts and motherboard and CPU will need some power too

I got two 850w psu's for a total of 1750w. That should be enough?

[CashbackLover]

I don't like the idea of using two power supply in a single mining rig, I'd rather go with big power supply or split the graphic cards and build two mining rigs instead of one, I just feel like it's more safer this way than using two power supply

[mantonio333]

I don't like the idea of using two power supply in a single mining rig, I'd rather go with big power supply or split the graphic cards and build two mining rigs instead of one, I just feel like it's more safer this way than using two power supply

Besides the phase issue, what else don't you like when using 2 psu's?

[th00ber]

Technically, 2 PSU will probably be safer.
Because you will have a lot of connector and you will be able to balanced the power on each cable

[miner29]

2 or even 3 psu is no big deal.

mobo all power from same psu
any gpus plugged directly into mobo all on same psu as mobo

any gpu on a riser should get all power to gpu and riser from same psu.....dont mix streams..

sync your psus either through 24pin Y or W cables or through mini 4pin if using server psus and breakout board.

And again respect the wattage limits for chains and connectors off psus.