CraptacularOne

Have you tried each card individually to verify they all work by themselves without issue?

Dirky

CraptacularOne

Have you tried each card individually to verify they all work by themselves without issue?

No I haven't as I have no issues with any 2 cards. It only crashes with 3 cards. It does no hardlocks or bluescreens, it just completely shuts off and reboots. All clocks are at factory, all I've done is enable XMP in the bios.

littleoldme

Probably not a problem with your power supply but it sounds like an issue with the cards drawing too many amps from the PCIe slots. When benching in sli mode keep an eye on your 12 volt voltage, if you see dips bellow 11.80 you must supplement your power going to the 12 line either with a mod to your 24 pin or perhaps get yourself an EVGA Power boost.

Dirky

Look for the green wire on the AX1200 or the backup PSU? What's making me think it's the power supply is that when it does it, it's just like hitting the reset button on the front panel, you can hear the psu switch off and then cycle up again to start running. I also had a 4 pin molex plugged into the board itself where the molex plug is for extra power for the pcie slots should you need it. 

CraptacularOne

littleoldme

Probably not a problem with your power supply but it sounds like an issue with the cards drawing too many amps from the PCIe slots. When benching in sli mode keep an eye on your 12 volt voltage, if you see dips bellow 11.80 you must supplement your power going to the 12 line either with a mod to your 24 pin or perhaps get yourself an EVGA Power boost.

Absolutely false. Even at 11.8 it's still well within ATX specifications. ATX specs for voltage regulation allow for a +/- of 5% so on a 12v rail that's either 12.6 or higher or 11.6 or lower. Furthermore, monitoring voltages from software apps is just a sad joke. They really shouldn't even include voltage monitoring in software because it's horribly inaccurate. You need a multi meter to properly test and diagnose voltages.

As for the OP, I'm beginning to think you have a faulty PSU. It's not out of the realm of possibility to get a defective unit. One way to test is that if you have a back up PSU that has 2 6pin PCI-E connectors that you can test with. I'll explain: All you need is a paperclip and the 2nd PSU. Then on that PSU look at the 24pin ATX connector and locate the green wire. There will only be one. And then take the paper clip and use it to connect the green wire to any of the black wires. . Now your 2nd PSU can be manually turned off and on by simply flipping the "on/off" switch on the unit itself. Use it to power the 3rd GTX570 and see if you still get a restart under stressing your system. If not, you've isolated the PSU as the culprit, if you still get a reset, the problem may be deeper and lie in software or perhaps the motherboard itself.

CraptacularOne

littleoldme

CraptacularOne

littleoldme

Probably not a problem with your power supply but it sounds like an issue with the cards drawing too many amps from the PCIe slots. When benching in sli mode keep an eye on your 12 volt voltage, if you see dips bellow 11.80 you must supplement your power going to the 12 line either with a mod to your 24 pin or perhaps get yourself an EVGA Power boost.

Absolutely false. Even at 11.8 it's still well within ATX specifications. ATX specs for voltage regulation allow for a +/- of 5% so on a 12v rail that's either 12.6 or higher or 11.6 or lower. Furthermore, monitoring voltages from software apps is just a sad joke. They really shouldn't even include voltage monitoring in software because it's horribly inaccurate. You need a multi meter to properly test and diagnose voltages.

As for the OP, I'm beginning to think you have a faulty PSU. It's not out of the realm of possibility to get a defective unit. One way to test is that if you have a back up PSU that has 2 6pin PCI-E connectors that you can test with. I'll explain: All you need is a paperclip and the 2nd PSU. Then on that PSU look at the 24pin ATX connector and locate the green wire. There will only be one. And then take the paper clip and use it to connect the green wire to any of the black wires. . Now your 2nd PSU can be manually turned off and on by simply flipping the "on/off" switch on the unit itself. Use it to power the 3rd GTX570 and see if you still get a restart under stressing your system. If not, you've isolated the PSU as the culprit, if you still get a reset, the problem may be deeper and lie in software or perhaps the motherboard itself.

Well these cards happen to pull over 50 amps and thats not within the spec either. 11.8 might happen to be within the spec but pulling that low causes problems downstream, 11.8 is right on the edge. Would you rather him burn up the 12 volt traces, or just simply supplement the voltage before it becomes a issue and have to do an RMA with ASUS, they aren't the most responsive company. There are only 2 12 volt pins on the 24 pin connector with very little surface area to play with.

False.....and actually not even in the same ballpark. Lets do some simple math shall we? 50 amps you say by one card? Not even on their best day could they even remotely get near that. Lets start by looking at the cards rated power draw which is 219w and honestly typically they don't even draw that much during normal games or daily use. But for the example we'll assume they are drawing 219w. The way you derive amperage is by dividing wattage by voltage. We know the card draws it's power from the 12v rail to that's 219w / 12v = 18.25 amps is what's drawn by the card if you stressed it 100%. If a card were to draw 50amps off the 12v rail it would take 600 watts to do that. Does that put it into a little better perspective? It's not going to happen.

Now onto 11.8v, no that's not "on the edge" it's actually a perfectly acceptable voltage range for your card to be in with the 12v line. 11.8v is less than a 2% variance on the 12v line and perfectly fine.

And finally the "power boost" Does not regulate nor does it provide "cleaner" power to the cards. All it is, is a aux source for 12v power (which conveniently violates PCI SIG standards by feeding power in through a PCI-E slot) for the cards to draw from rather than the 24pin ATX cable. It has no regulation ability to the 12v line nor does it stabilize it. It's actually not even passed through the boards pwm phasing to "clean" the power like the current that is drawn from the 24in ATX connector.

Regardless of all this though, as his board already has an AUX molex power input so the need for a power booster is irrelevant.