3x R9 280x with PSU Antec HCG-900 900w?

[revvv]

Hi guys,

I am making a new rig, the shop I am buying for sold me a HCG-900 to power 3x R9 280x. I am back home but I am having doubts, do you think it's enough?

[j0achim]

Its tight. Depending on which 280x card you run they pull anything from 275-350w 220-330w and at 350 330 that will over time overload yer PSU and eventually it'll fizzle out.

That being said you can undervolt the GFX cards so that they do not run at full wattage, and in some cases this have no effect on hash rate at all.

[revvv]

Thanks for the info. They are gigabyte GV-R928XOC-3GD.

[bitcoin-world.de]

I have undervolted my gigabyte R280x and underclocked it and it runs about 720khash/s with less energy consumption. I can recommend all to do this, because the GPU runs cooler, less noise and can live more. But the problem is I´ve done this manually, because I didnt find any modificated bioses.

I have also done this with the older Gigabyte 7950 and it runs about a half year now without problems and two of my friends had many problems with the original bios. The GPU´s from Gigabyte run very hot and the Cooler runs at 100% always with the original BIOS. I can recommend all professional people who know how to do this to do this if you dont want to send your GPUS to the Manufacturer and wait 4 Weeks until they are back.

[revvv]

what voltage did you put them? what about underclocking?

I have a rig with 2x 280x. one is 69celsius other 91celsius running fun 100% speed all the time. Sometimes the cards stop working, the fun keeps moving but there is not video output. I have to shut the rid wait few seconds and turn it on again. Whats the problem? Temp? PSU?

[j0achim]

91 degree is too hot. and may cause malfunction over time. i find that even at 88 degree over time it causes hardware errors in my rigs.

[gencoinx]

I have undervolted my gigabyte R280x and underclocked it and it runs about 720khash/s with less energy consumption. I can recommend all to do this, because the GPU runs cooler, less noise and can live more. But the problem is I´ve done this manually, because I didnt find any modificated bioses.

I have also done this with the older Gigabyte 7950 and it runs about a half year now without problems and two of my friends had many problems with the original bios. The GPU´s from Gigabyte run very hot and the Cooler runs at 100% always with the original BIOS. I can recommend all professional people who know how to do this to do this if you dont want to send your GPUS to the Manufacturer and wait 4 Weeks until they are back.

Hi, can you tell me what are your settings in your 280x? Like gpu clock, memory clock and voltage? I'm also trying to undervolt it, just having a hard time finding the right settings.

Thanks in advance

[bitcoin-world.de]

the gigabytes are voltage locked. You have to modifcate a bios to undervolt them. I am at work now and cant look for the voltage. If you want I send you my bios for a some coins, because I´ve tested it 50 times and it was very hard to find the right settings. Make me an offer.

[Catswold]

What you are seeing is due to excessive temperatures.  The R9 series have a cut-out to prevent over-clockers and the rest of us from burning up our cards.  The R9 series AMD cards are made to run hot--95C is the limiter temp (the point at which the card forces clock speed down to ~70%).  91C will not damage the card, but it is a whole lot of heat and if you are seeing that reported, you are probably bouncing off the 95C limit.

Running 3 R9 280x cards on a 900W PSU is really pushing it.  You really need 1100 or more to prevent starving your cards of power.  That being said, under-clocking does resolve some of that difficulty.
 
Problem is, Gigabyte cards are voltage locked, so the only means of lowering the voltage is by flashing the bios from one of the competitor cards that is not voltage locked.