HW problem. Windows boots up with 3 cards, not with 4

[zeezoo]

Hello,

I've got 2x R9 290 4GB, 1x 470 4GB, 1x 570 4GB. 750W 80GOLD PSU
I've mined for about 1 month with these 4 AMD GPU's without any trouble.
HW set up was my personal PC: HP Pro 3500 MT with i7 CPU 3370 and 16GB DDR3 on Windows10.

I thought that would be a waste of HW and bought ASUS P5W DH on i975x with Core2Duo E8400, installed Windows 7 SP1 as Win10 reboots by itself after updates.
PC boots normally with 3 cards attached, but with 4 freezes on "Starting Windows", keyboard light goes off and screen freezes. Safe mode is also unable to boot.
I've tried to remove each and every card, as well as use different PCIE ports but it always boots up with 3 cards, freezes with 4.

Would that be an issue with PCIE lanes provided by CPU?
I've read that 4 GPU's are possible to work on i975x chipset.

Drivers are up to date - I installed INF_allOS_9.1.2.1008_PV.exe

Any advise? Maybe BIOS settings?

Regards,
zeezoo

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[tg88]

Have you tried other risers? sometimes the problems are in the adapters.

[adaseb]

Yes like the above poster says.

You most likely got a bad riser somewhere. The other rare issue can be is that one of the GPUs is starting to die.

I had that happen but that was mostly with very old and tired GPUs.

[zeezoo]

Basically I swapped risers around and they all seem to work fine separately... but not together...

I just moved it back to previous machine and it seems to work fine...

[EDIT]

I realised that if I wait 3-4 mins to boot up the machine it actually boots up but it's super slow... CPU usage at 100% all the time.
Tried to install ubuntu on 1 card and then with 4 cards it also hangs before grub...

Must be an issue with pcie lanes... Maybe E8400 won't provide enough.

I even connected another PSU to power up Mobo and risers as well as 2x 6pin pcie connectors but the problem is still the same... Well I guess I would need another motherboard for this project...

I've connected RX570 on one riser and mined for 1 hour, then swapped to another riser normally connected to R9 290, mined for 1 hour.
Then swapped 570 with 290 mined again for 1 hour on 1 riser and 1 hour on the other and it seems to work just fine, hence I don't think it's a riser problem.

Regards,
zeezoo