Dual PSU Woes - 3GH/s w/ 3x5970 + 2x5870 - page 2.

JWU42

legendary

Activity: 1666

Merit: 1000

It is an issue with BAMT...

Nope on the powered extenders...

Have gone to 2x5970 and 3x5870 for now = 7 GPUs. Working fine at 2.8 GH/s Grin

check_status

full member

Activity: 196

Merit: 100

Web Dev, Db Admin, Computer Technician

Are you using any PCIe extender cables?

JWU42

legendary

Activity: 1666

Merit: 1000

I am running the x64 version - should have mentioned that...

Code:

root@kong:/opt/bamt# uname -a
Linux kong 2.6.32-5-amd64 #1 SMP Mon Jan 16 16:22:28 UTC 2012 x86_64 GNU/Linux

Didn't realize the X64 didn't fix the 7 GPU max limit though...

AniceInovation

donator

Activity: 446

Merit: 262

Interesting.

BAMT only takes 7 GPUs, lodcrappo thought on moving BAMT to x64 and so support 8, but it's showing as problematic for some beta testers, and he is giving up on the idea.

JWU42

legendary

Activity: 1666

Merit: 1000

UPDATE...

Have moved the main PSU to a Corsair 950 and the secondary as Seasonic Gold 750.

Good news - all 5 cards show up - with a minor caveat...

The 5970 on the secondary PSU only has 1 core showing active -- so 7 GPUs total.

Any bright ideas?

Code:

root@kong:~# aticonfig --lsa
* 0. 03:00.0 ATI Radeon HD 5900 Series
  1. 04:00.0 ATI Radeon HD 5900 Series
  2. 07:00.0 ATI Radeon HD 5900 Series
  3. 0b:00.0 ATI Radeon HD 5900 Series
  4. 0c:00.0 ATI Radeon HD 5900 Series
  5. 10:00.0 ATI Radeon HD 5800 Series
  6. 11:00.0 ATI Radeon HD 5800 Series

* - Default adapter

JWU42

legendary

Activity: 1666

Merit: 1000

Thanks guys - 2 things I should have made clear earlier (hastily posting earlier).

1. Total watts should be 1250 at the wall. Assuming 88% efficiency the PSU is providing ~1100 watts or roughly 73.33%.

2. I am struggling to get it to properly load all 3 5970's even without the last 5870 thrown in. It seems that the 2 x 5970 on one 750 is causing problems but believe I have seen others using this combination of PSUs w/ 4x5970.

rjk

sr. member

Activity: 448

Merit: 250

1ngldh

Quote from: BkkCoins on February 08, 2012, 07:17:44 PM

The only thing that comes to mind here is DON'T split a card between two PSU. I've never tried that but I'm pretty sure that would cause problems. Each PSU has potentially slightly different voltage outputs and this would cause some cross currents between the supplies as they try to "merge". Depending on how the board power connectors actually hook together and what components run off each one there could be various other effects.

I'm not a 5970 user so I don't know what they draw. I would think that 2x5970+MB on one 950W PSU should work and 1x5970+2x5870 on the other one. Definitely don't split a GPU between 2 PSU.

From a strictly engineering perspective, this would usually be true, but according to the PCIe spec it should work fine. ArtForz has posted on this issue several times with links to the technical documents explaining why.

However, I do think you could be underpowered still, OP. I never run my PSUs beyond 50-60% load, and with that hardware combo you might be pushing it over 80-90% load which might have stability issues.

BkkCoins

hero member

Activity: 784

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firstbits:1MinerQ

The only thing that comes to mind here is DON'T split a card between two PSU. I've never tried that but I'm pretty sure that would cause problems. Each PSU has potentially slightly different voltage outputs and this would cause some cross currents between the supplies as they try to "merge". Depending on how the board power connectors actually hook together and what components run off each one there could be various other effects.

I'm not a 5970 user so I don't know what they draw. I would think that 2x5970+MB on one 950W PSU should work and 1x5970+2x5870 on the other one. Definitely don't split a GPU between 2 PSU.

JWU42

legendary

Activity: 1666

Merit: 1000

Been trying to achieve a 3 GH/s box. Specs below:

AsRock 970 Extreme 4MB
1 x 2GB ram
Sempron 145
2 x 750 Seasonic Gold (usign Add2PSU adapter)
Running BAMT (USB Key)

I have had it running 2x5970 and 2x5870 and 1x5770 for a day or two. Added a 3rd 5970 with just one 5870 and it booted and mined OK. Then went for the final 5870 and it all fell apart. Now I am unable to get even a single 5970 working off the secondary PSU.

My plan was:

Main PSU
- MB
- 1 x 5970
- 1 x 5870

Second PSU
- 2 x 5970
- 2x10W Delta screamer fans (someone mentioned putting some 5v load on a secondary PSU).

The last 5870 was being powered via dual 4pin molex to 6pin PCI-e with each PSU pushing one of the 6pin plugs (2x4pin molex).

Any words of wisdom here? Maybe use a 950 as the secondary PSU (gives it more headroom with 2x5970). Put the 2x5970's on the main PSU?

Yes, I understand that a 1500W PSU would be simpler Roll Eyes

So all you folks running 1200W+ rigs what have you learned with respect to what cards where on multi-psu setups.

I am planning to mess with it some more this evening but would love some pointers if I am missing something simple.

Thanks in Advance!

EDIT -- Yes, the 5970's are in the x16 slots and the 5870's are in x1

Topic: Dual PSU Woes - 3GH/s w/ 3x5970 + 2x5870 - page 2. (Read 7778 times)