System only sees 2 of 3 GPU's (1070GTX)

[SidETH]

Ok I'm officially stuck

I'm running 2 1070GTX without any problems, but when adding the thirds the system simply doesn't see the 3rd GPU card.
- Tried updating the BIOS of the motherboard (Biostar TB250-BTC), but no change.
- Tried updating the Nvidia drivers (now 382.33), but no change.
- Tried switching rizers, no change.

Rest of the system:
4gb ddram
120gb SSD
Intel pentium
Windows 10

[Vann]

Did you change the 1x PCI-E slots to PCI-E v1.0 in the Bios? Did you install Windows 10 in UEFI mode?

[SidETH]

I now have them on Gen 2 because of this video: https://www.youtube.com/watch?v=Wlxxzax7MgY
Windows UEFI... let me Google it Edit: don't think so. Just a regular install.

[Vann]

I now have them on Gen 2 because of this video: https://www.youtube.com/watch?v=Wlxxzax7MgY
Windows UEFI... let me Google it Edit: don't think so. Just a regular install.

Apparently you didn't RTFM either. The motherboard specifications say you should use PCI-E 1.0 in the Bios.

http://www.biostar-usa.com/app/en-us/mb/introduction.php?S_ID=865#specification

5 x PCI-E x1 3.0 Slot(using for bitcoin mining, it is suggested to change to PCI-E 1.0 via BIOS)

You also need to plug in the two Molex connectors on the motherboard.

2 x PCI-E 12V 4Pin Connector(Must be installed when using for bitcoin mining.)

How to test whether Windows 10 was installed with UEFI?

https://superuser.com/questions/946868/how-to-test-whether-windows-10-was-installed-with-uefi

[SidETH]

You also need to plug in the two Molex connectors on the motherboard.

2 x PCI-E 12V 4Pin Connector(Must be installed when using for bitcoin mining.)

This fixed it. It's now detecting 3 and 4 cards. Thanks!

Only now the mining is highly unstable (speeds from 5 Mh/s to 110 Mh/s).
Cards are stock (not overclocked yet).

When running 3 cards it's working fine at a stable 75 Mh/s.

[SidETH]

Up and running, 5x 1070. I changed the risers for another (6-pin) model and now all is fine.
With a little clocking just a bit under 150 mh/s avarage. I think it's OK like this
Thanks again for the help.

[Vann]

Up and running, 5x 1070.
With a little clocking just a bit under 150 mh/s avarage. I think it's OK like this
Thanks again for the help.

30 MH/s for a 1070 is very good. Congrats!

[SidETH]

Thanks.

How about the 800W power consumption?
The GPU's get around 65 degrees Celcius. Any ideas on this number?

[Vann]

Thanks.

How about the 800W power consumption?
The GPU's get around 65 degrees Celcius. Any ideas on this number?

Try lowering TDP to 70% in afterburner. That should drop the power quite a bit. You also may need to drop the core for it to be stable.

[SidETH]

I lowered it a bit now without dropping the core (will first have to update my very limited (!) knowledge on that), not a huge different but it's still stable so I'm happy. Temperature is stable in the 61-63 degrees celcius range.
Power costs here is ±0,16 euro per kwh. So it costs about 100 euros per month now if I'm correct to run it 24/7.
Will try to bring that a bit further down next week after running is stable for some time.

[SidETH]

Now at a steady 149.5mh/s and 650W power drain.
Thanks Vann.

[Vaccinus]

maybe the third gpu is faulty? did you try to switch the gpu also to see if this is not the case? another thing could be the psu, what psu do you have? maybe it can't handle all 3 gpu