PSU Corsaire AX1200 power limit

[silenas]

Hi everyone,
Here's the situation:
I have an AX 1200 (corsair). Plugged to a B250 K4.
On this I finally achieved some weeks ago a constant stability with 4 GPUs, and today added the 5th.
- 3 RX580, 1 RX480 and ... 1 R9 390 - which I know count almost for 2 in term of power...
At boot, I got a grey screen with blinking squares like a good'old christmas tree when the final card is plugged. Any of the 4 plugged is fine. So it has to be a lack of power ... right? (that's be my first confirmation if I can get any).

Then comes the question: Is there anything I can do to make this happen, and if not, will a 1300W PSU be sufficient? (Please don't shoot at me not doing the math on power and consumption because obviously, I got it wrong, else I wouldn't have 5 GPU (esp. a R9 390) with this PSU)...

Thank you very much for your time and knowledge

Best Regards
S.

PS: Yeah - I went to the BIOS, disabled anything I could find was not useful to manage a CPU and some GPU and memory + 1 USB port (can't telepath commands to the computer... yet).

 

[mdd1963]

If the 390 counts as adding two (power-wise), then try removing one or two lesser cards, then adding one, then another...

It's also possible the motherboard is simply incapable of supplying all 5 cards with the 60-75 watts each thru the PCI-e slots....

 

[silenas]

If the 390 counts as adding two (power-wise), then try removing one or two lesser cards, then adding one, then another...

It's also possible the motherboard is simply incapable of supplying all 5 cards with the 60-75 watts each thru the PCI-e slots....

Hello
Thank you - yes I pointed at what you said, each 4 cards setup is working fine, so not a card issue. Only adding the 5th (whichever) is causing the problem. But I need to know if this is the motherboard or a PSU issue. I will try to take a closer look at the mobo specs later tonight.

 

[silenas]

Hi All
Ultimately, the answer was in setting the TOLUD in BIOS from Auto to 3.5 Gb.

 

[silenas]

Hi -
Conclusion to the original question:
So the grey screen was solved by setting TOLUD to maximum.
I found this website I wasn't aware about on some forums as well: https://outervision.com/power-supply-calculator
With it, I found out that I was at 94% of the PSU (I did not mod any of the component, so all standard default). The recommandation from this tool, which is also used by coolermaster provider was still a 1200W PSU.

So here we go, started the system, let it run for 18h no problem.
The next evening, after starting the system again, and running it for 3 hours, I smelt an unusual smell - burning.
I checked everywhere. System was not behaving badly, temperatures of CPU at a breezing 35C, GPU all below 80, the highest at 79C which has been the standard temperature of that specific card (the 480) when running on 4 GPU for many weeks. I have no sensor on the PSU, but touching the back of the PSU and sensing the airflow around the PSU wasn't alarming. It was not hot. At least, certainly cooler than the alluminium support where the 480 (79C) is attached.

Unable to spot where this was coming from, I shut the computer since it never happened before.

I saw somewhere that it is preferrable to keep the PSU under 80% usage. That may just be a confirmation.
I have removed the lastest 5th GPU from the system while I consider my options, hoping the PSU did not suffer any specific damage.
If anyone has a comment, let me hear it.

Thx and have a great day all.
S