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TX 650V2 enough for crossfire..

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Successfully Trolled by Megalith
Joined
Jul 18, 2010
Messages
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I'm thinking of picking up another 280X for crossfire and 3x monitor gaming with mining during downtime. I'd be undervolting the GPUs as far as possible while keeping stock core/RAM settings.

Q1: My main question is if my PSU will be enough to handle it. I have a Corsair TX 650 V2. It only has a pair of 6+2 connectors. I'd be running an 6+2 pin PCI-E connector to each card's 8 pin slot, then running an adaptor to each card's 6 pin slot.

Q2: Also, would I want to put each card on it's own molex line for the 6 pin using adaptors, or would I want to plug in a 12v from each line coming out of the PSU to each adaptor (so the cards are sharing both molex lines)?

The case contains:
4xPlatter HDs
1xSSD
2x200mm fans
3x140mm fans

I run the 2500K 4.4GHz @ 1.315v.
The first 280x runs 1000/1500 @1.050v (down from 1.2v stock). I'd be undervolting the second one as well.

I put a Kilawatt on and while mining power consumption is at 360watts at the wall. Stopping mining and prime95ing added 68 watts, so I'm guessing that in my current system total max power draw with CPU and GPU maxed would be 425-430w @ the wall. I'm guessing that my PSU is ~85% efficient at that draw, so the PSU should actually be putting out 365 watts to the system or 30.4amps on the 12v rail if everything is 12v load. The TX 650 is rated at 53 amps 12V.
 
A1: I think it will not be enough to handle it.. you might be in the barely minimum and not for high loads specially if you have a overclocked CPU. the total load for 2x 280X its i think in the line of 500W so the whole system while gaming could be arround 640W and nobody in this life want to have a PSU running in 90% of usage I wouldn't put in anything less than 750W bronze rated PSU just to be safe.

A2: the PSU its single rail so not matter really what cables go to whatever card, the PSU will not distinguish where its connected. you have only to be cared about that if you have a multiple 12V rails PSU.

in fact about the PSU people tend to recommend a 600W-650W PSU only for one 280X.. depending on what kind of intel or AMD CPU people will use.. but remember you are on a overclocked sandy so i guess that CPU should draw like 100+W at 4.4ghz. adding RAM, MOBO, FANS. etc.. your load will be passing from 650W.
 
No, not enough power. HardOCP's load testing of a setup with an i7 3770K @ 4.8Ghz, a single hard drive, and two HD 7970 cards was around 667W at full load.

Since the R9 280X is basically a rebadged HD 7970, those power draw figures should still be similar.
 
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