Powering Asus B250 Mining Expert from 3 phases

Denis Črnič · 21 Apr 2021 at 15:42

I've obtained Asus B250 mining expert MoBo, which has 3x 24 pin ATX power connectors on board. For powering it I'll be using 3x Power CXT 2000 W PSU which on max. load would be pulling about 25 A, which would be on a limit of a 25 A breaker (230 V) if I were to use all 3 PSUs on a single phase.

I'm considering using each PSU on one of three phases (8 A per phase). That shouldn't be the problem for my electrical installation, but 2 new problems arose.

In order not to fry MoBo or graphic cards I'm pretty sure I shouldn't let only 1 phase get cut off (which happens from time to time, due to maintenance on grid). For that case I'm willing to setup my own electrical panel which would cut off all 3 phases in case one goes off.
Is there any chance for any interference (any kind of problems which could arise between phases) and am I risking to fry anything if I connect 3 different phases to 1 MoBo?

Also I'll try to get to work 18x Asus Strix 3090 rtx on that one single MoBo. I'd be glad if anyone could point out any problems that could arise during installation of rig (pins/cables/risers getting fried ... ).

For powering 2 risers I'll be using 1x 6 pin -> 2x 6 pin Y splitter

For powering 3090 I'll be using 2x 8 pin (+ riser). I was wondering if is it necesarry to plug all 3 8 pins to the graphics card? I'll limit the power draw to 320 W/card. As far as I know it's safe to draw 75 W through riser + 285 W through 1x 8 pin cable, but I was just wondering what you guys think. Trying to keep it safe, don't wanna cause any damage to the setup

Cyber-Mav · 22 Apr 2021 at 11:57

three-phase voltage 415v, i dont see why you need 3 phase power for home computer.

Denis Črnič · 22 Apr 2021 at 12:01

It's not a home computer at all, it's an "industrial" mining rig with 3x 2000 W PSU (3x ATX connector, picture below), which in total would exceed power draw on single phase.

Thekwango · 22 Apr 2021 at 12:04

You’ve 18 3090’s?

Denis Črnič · 22 Apr 2021 at 12:06

Not yet, but am planning on getting them if the setup with this MoBo would work with 18x 3090s, that's why I'm asking first, before doing anything stupid

.

Disco_P · 22 Apr 2021 at 14:55

Well in that case, buying 18 3090s would be stupid.

Denis Črnič · 22 Apr 2021 at 15:00

Explain why you think buying 18 3090s would be stupid?

Disco_P · 22 Apr 2021 at 15:37

Denis Črnič said:
Explain why you think buying 18 3090s would be stupid?

What is your return on investment period and what assumptions are you making to get to that number?

Denis Črnič · 22 Apr 2021 at 15:47

My numbers are 1800 MH/s at 6000 W of power usage, 0.18$/kWh.

I return my investment in 250 days by current mining rates.

Armageus · 22 Apr 2021 at 15:58

Not sure why that board has 3x ATX connectors, or why you need 3x 2000W PSUs to power it.

Even with 18x PCI-E slots, the most they could draw is 25 W each = 450W?

And even then, risers typically supply power separately (i.e. 75 Watts from a 16x Slot).

Joxeon · 22 Apr 2021 at 16:47

Denis Črnič said:
Explain why you think buying 18 3090s would be stupid?

Assuming you have easy access to cards if you managed to get 18 of them then surely it would be better buying 36 3060tis as these would give a better hash rate while using less power and being half the price of the 18 3090s. So ROI would be halved.

Denis Črnič · 22 Apr 2021 at 17:19

You don't need 3 PSU-s to power it, it also works with only one 300 W PSU plugged into ATX A section and CPU pins, but it has a capability to power 3x 6 PCIe through those 3x ATX pins as far as I "think" (don't know for sure, that's why I'm asking, if there's anyone who has any experience with this MoBo).

Risers are powered through 6 pin directly from PSU (through Y splitter, so 1 PSU 6-pin cable splits into 2x 6-pin to power 2 risers.), so I'm pretty sure each card can pull 75 W through it's riser., each GPU is also powered through 2x 8-pin directly from PSU.

Schematics of my setup:
https://prnt.sc/11vofjo

Purple: 24-pin ATX
Blue: USB 3.0
Brown: Molex
Green: 6-pin
Red: 8-pin

https://1.bp.blogspot.com/-vAhFuH5G...T8zkhyNbae69o5MjJtC89QCLcBGAs/s1600/PCIe2.png
According to this image I should have no problems if I limit GPU's to run on about 300 - 320 W/GPU.

Let's just say that I can get 3090s easier and earlier for exactly twice the price of 3060s. But then again for 3060s I'd need twice as much hardware (MoBo, CPU, SSD, stand, fans ... ), twice as much space, not to mention that 2 rigs with 18x 3060s would probably draw more power than 1 with 18x 3090s.