Is it safe to use a PSU to power cards from 2 different rigs?

[thehun]

Here is the situation:

I have 2 rigs with 3 7950s on each of them and 2 Corsair CX750 PSUs. The first rig is running perfectly with the first PSU (crashes sometimes but very seldom) but on the second one I can't run more than 2 cards at a time. If I plug in the 3rd one the system crashes after a few minutes of mining (and I can't turn it on again until I have turned off the PSU and waited for some time).

I'm thinking about getting a 3rd CX750 to power one card from each rig to take some work away from the other 2 PSUs, but I'm not sure if this can be done safely. My interpretation is that if I power the risers and the cards with the 3rd PSU (so they don't draw any energy from the other PSUs) there won't be any electrical connection between the two rigs. But of course I might be missing something. I'm using 30cm powered risers for all cards.

[tom_o]

Here is the situation:

I have 2 rigs with 3 7950s on each of them and 2 Corsair CX750 PSUs. The first rig is running perfectly with the first PSU (crashes sometimes but very seldom) but on the second one I can't run more than 2 cards at a time. If I plug in the 3rd one the system crashes after a few minutes of mining (and I can't turn it on again until I have turned off the PSU and waited for some time).

I'm thinking about getting a 3rd CX750 to power one card from each rig to take some work away from the other 2 PSUs, but I'm not sure if this can be done safely. My interpretation is that if I power the risers and the cards with the 3rd PSU (so they don't draw any energy from the other PSUs) there won't be any electrical connection between the two rigs. But of course I might be missing something. I'm using 30cm powered risers for all cards.

Very electrically risky, just get a 1000w PSU.

[thehun]

Here is the situation:

I have 2 rigs with 3 7950s on each of them and 2 Corsair CX750 PSUs. The first rig is running perfectly with the first PSU (crashes sometimes but very seldom) but on the second one I can't run more than 2 cards at a time. If I plug in the 3rd one the system crashes after a few minutes of mining (and I can't turn it on again until I have turned off the PSU and waited for some time).

I'm thinking about getting a 3rd CX750 to power one card from each rig to take some work away from the other 2 PSUs, but I'm not sure if this can be done safely. My interpretation is that if I power the risers and the cards with the 3rd PSU (so they don't draw any energy from the other PSUs) there won't be any electrical connection between the two rigs. But of course I might be missing something. I'm using 30cm powered risers for all cards.

Very electrically risky, just get a 1000w PSU.

Makes sense. But it's not so easy to find a PSU with sufficient PCI-e outputs at a reasonable price (and it's quite hard to get splitters here)