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While sometimes it is more economical to have multiple rigs running (for power and cooling reasons), I am limited by the number of systems I can operate in the house. Having said that I would like to know if there is any way to power 4 unlocked (880MHz or OC 900Mhz) 6990s out of two Thermaltake 1200W PSUs (model number W0133RU). I have a case which supports dual PSUs (TJ07), and the ATX adapter cable which turns on the second PSU when I switch on the power.

Here is the problem. While 2400W combined "should" be enough for practically anything, I would like to know if I would be overloading the 12v ATX rail (4 GPUs + Phenom II X6 1090T/890 chipset. There is no way to "glue" the power of two ATX rails. I know that the CPU rail is there to help out, but I don't know if it will be enough.

I will invest in external watercooling to keep things running smoothly, so heat will not be an issue, and the cooling won't burden the PSUs.

Any thoughts?

just to be clear, are you specifically refering to the molex adapter on the motherboard that is only used for crossfire/SLI ?

interesting question, something I personally would like to know!

By the adapter, I mean a dual power supply ATX motherboard adapter cable like this:
http://www.frozencpu.com/products/5637/cpa-167/Lian_Li_Dual_Power_Supply_Adapter_Cable.html

Thanks for the tip on that one!

If you run them on cheap processors the total power usage will be 1900-2000W at peak times. Those PSUs will run them more than fine.

ah, always wanted one of these instead of having to tape down a dodge bit of wire haha

With regards to total power there is no problem. Where I see a possible problem is in the overloading of the individual rails from the PSUs. Since I can only use 1 PSU's ATX rail to power the motherboard, I am only working with 20A from the ATX connector and possibly 20A from the CPU connector.

The 6990 uses 75W (from MB) + 2x 150W (8 pin PCI-E) while operating at 830MHz for a single card (375W total). My question is if the card is overclocked and uses more power, will the power usage grow proportionally from each source, or will the PCI-E connectors compensate the difference required, leaving the MB slot draw at 75W.

Thoughts?

may I ask what kind of case u use ?

Silverstone TJ07.

You should have no problems at at all, I didn't look up the specific PS so this may not be an issue but just pay attention to what 12V you have things on so you don't overload a given rail and with that you will be fine.

Thank u ! Looks good !


I am trying to set up 10 systems with 4x5870 ! but no matter where i look i don`t find a case where i do not get problems with cooling the 4th card..!

don´t u think u`ll run into same problems ?

4x6990 will produce hell of a heat!

Better get a TJ11. The TJ07 has lots of heat problems, plus you won't be able to put in the 4th card without a dremel. I will use water cooling, so it's a non-issue, right now I underclocked the cards to keep them cool.

okay with watercooling that should work!

TJ11 costs 500euro :D won`t work out ^^

u know a thread about getting the problem solved with 4x8570 in an Cooler Master HAF X ??

thank u for ur help! and sorry for hijacking ur thread for a few questions :D

How about this?

Get a Kill-a-watt
Set up a 2x6990 rig (locked, normal clock speeds)
Record the at the wall wattage. (lets say X)
Measure how much power the PSU cabling is providing the cards. (Y)

Now overclock
Record the at the wall wattage (lets say X_2)
Measure how much power the PSU cabling is providing the cards. (Y_2)

Now you should see
X_2 = X + B (where B is the additional power being draw after overclocking, unlocking and increasing power through CCC, etc)

If B = Y_2 - Y then I'm assuming you must be in the clear since the total power difference would be known to be provided directly from the PSU.

Also, how about simply calculating the proportional difference (if there might be one) and locating a motherboard that has that spec?

Also, also, wouldn't the motherboard be limited somehow?