I suggest you try running three cards - since two is ok, and four is not ok, how about three? This should all run ok from the one 1000W power supply. My 3x7950 takes about 850W from one 1200W psu. If this is ok, try the third card in the other slot - you may have a slot problem, not unknown.
Also as mentioned, power supplies often have multiple 12V rails - try to spread the load across the rails. If you have some of the newer psu's - they are quite often single rail, so easy to work with. In any case, using two psu's should be good.
Topic: Help me configure a 4 HD7950 Rig (Read 611 times)
I had a very similar issue and couldn't figure it out for the life of me for the longest time. I am running 4 cards also with 2 PS, but they are 290's and 7970's.
What fixed my issue was plugging the modular PCIe power connectors into different slots on the power supply. All the pci-e ports on my PS are powered from the same 12V rail so it really doesn't make any sense that would fix the issue, but it did.
Are you running 2 cards off each PS? Can you take pictures of your setup to verify everything is hooked up properly? Do you have a device to measure the power being pulled from the wall?
What fixed my issue was plugging the modular PCIe power connectors into different slots on the power supply. All the pci-e ports on my PS are powered from the same 12V rail so it really doesn't make any sense that would fix the issue, but it did.
Are you running 2 cards off each PS? Can you take pictures of your setup to verify everything is hooked up properly? Do you have a device to measure the power being pulled from the wall?
I'm not using molex to pci only using cable who comes with the psu , my riser seems to work good.
The second psu is a Coolermaster V850, the cards are all Sapphire HD7950 Dual-x 3Gb Vram and all looks the same, yes i'm powering gpu and risers with the same psu, sorry but it didn't help
The second psu is a Coolermaster V850, the cards are all Sapphire HD7950 Dual-x 3Gb Vram and all looks the same, yes i'm powering gpu and risers with the same psu, sorry but it didn't help
are your risers connected to the same power supply as the mobo?
What is the second PSU ?
Is the cards compleatly identical?
Do you power the risers only from the psus to which the videocards is conected? For example, you connect two first cards to one psu and power risers for those two from first PSU, that would be the right order. Also those powered cabled to motherboard should go only from primary PSU. So that secondary PSU would power only two cards and risers to those two cards. If my advice helped, write me
Is the cards compleatly identical?
Do you power the risers only from the psus to which the videocards is conected? For example, you connect two first cards to one psu and power risers for those two from first PSU, that would be the right order. Also those powered cabled to motherboard should go only from primary PSU. So that secondary PSU would power only two cards and risers to those two cards. If my advice helped, write me
check cables. in my case, I had some melted molex-pci-e connectors. one of the yellow wires melted as well.
check the powered riser cables are good. i had 1 brand new one defective
check intensity of all the cards in your miner, may have to set each one individually.
check the powered riser cables are good. i had 1 brand new one defective
check intensity of all the cards in your miner, may have to set each one individually.
Just a guess, but I think you're pushing the primary PSU to the limit. Try running a 3rd card off the secondary PSU and if that's stable then that's an indication that it's the 1000 watt psu being pushed too hard from the 3rd card.
People with killawatts have measured 3 7950s from the wall anywhere between 700ish (heavily undervolted) to over 1100 (heavily overclocked) I would guess you're between 900 and 1000 for your system not knowing your cpu specs running the 3 cards at max.....
That cooler master V1000 psu is rated at 996 watt on the 12v rail with 87% efficiency for 80 plus gold rating at 100% load is 866.xx watts....
You can try undervolting the cards as well if you determine it's the psu limit being reached.
People with killawatts have measured 3 7950s from the wall anywhere between 700ish (heavily undervolted) to over 1100 (heavily overclocked) I would guess you're between 900 and 1000 for your system not knowing your cpu specs running the 3 cards at max.....
That cooler master V1000 psu is rated at 996 watt on the 12v rail with 87% efficiency for 80 plus gold rating at 100% load is 866.xx watts....
You can try undervolting the cards as well if you determine it's the psu limit being reached.
Hi i get some problems with my mining rig
Since i added 2 gpu (Sapphire hd7950) my rig became unstable.
When i launch cg miner it work well but after a few minutes 2 of my gpu start to fail, khash are changing constantly between 450 and 510khash, the 2 others card are working great btw but after a random time i always get a bsod
I'm running these gpu on a Asrock h61 btc pro mobo with 2X2 go of ram, i got one cooler master V1000 psu for 3 gpu and a cooler master V850 psu for 1 gpu and i'm using powered risers.
I also plugged the 2 SLIpower molex on the mobo
When i disconnect 2 gpu it's working well, it's really when i start mining with 3 gpu that problems occurs.
I'm not overclocking the gpu, running them at stock clock, Engine at 925 and Mem at 1250mHz.
My .bat is the following :
cgminer.exe --scrypt -o stratum+tcp://freedom.wemineltc.com:3334 -u kewomot.amd -p t --thread-concurrency 21712 --gpu-engine 925,925,925,925 -I 17,17,17,17 -w 256 -g 1 --gpu-fan 75,75,75,75
Thank you
Since i added 2 gpu (Sapphire hd7950) my rig became unstable.
When i launch cg miner it work well but after a few minutes 2 of my gpu start to fail, khash are changing constantly between 450 and 510khash, the 2 others card are working great btw but after a random time i always get a bsod
I'm running these gpu on a Asrock h61 btc pro mobo with 2X2 go of ram, i got one cooler master V1000 psu for 3 gpu and a cooler master V850 psu for 1 gpu and i'm using powered risers.
I also plugged the 2 SLIpower molex on the mobo
When i disconnect 2 gpu it's working well, it's really when i start mining with 3 gpu that problems occurs.
I'm not overclocking the gpu, running them at stock clock, Engine at 925 and Mem at 1250mHz.
My .bat is the following :
cgminer.exe --scrypt -o stratum+tcp://freedom.wemineltc.com:3334 -u kewomot.amd -p t --thread-concurrency 21712 --gpu-engine 925,925,925,925 -I 17,17,17,17 -w 256 -g 1 --gpu-fan 75,75,75,75
Thank you
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