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750w for 2 7970s?

Y

y2kcamaross

n00b
Joined
Aug 15, 2011
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I have a 3770k@ 4.9 with 1.38 volts running throught it and 2 GTX680s. I just traded the 680s for 2 7970s, the entire system with the 680s never pulled more than 630 watts from the wall(kill a watt)the entire time I've had them(since march). Do you think the 750 watt power supply(ocz zt 750, 62a on the 12v rail) will be enough with everything overclocked? I know the 7970s draw alot more power than the 680s especially when overvolted. I just want to know if I'm gonna need a new PSU so I can order one before these arrive, thanks!
 
You shouldn't pull a lot more than the 680. Using a killawatt I never got more than 380W on the wall with my one 7970 and 3570k overclocked. That being said, don't know how well the OCZ 750W performs, but if it can do 600W continuously you should be fine.
 
While I would never recommend the ZT series (Great Wall made mediocrity), it should do the job. Just make sure your ambients are low. The ZT has a very aggressive temp protection.
 
I've already replaced the fan in the ZT because of how annoyingly loud it got, I guess we'll see, if it doesn't do the job I'll just buy a 1000w+ psu, I know my buddy with a 2600k/2 7970s pulled over 1000 watts on my killawatt when he loaded up prime95 and furmark, but he also has everything watercooled with multiple pumps etc, and I'm not sure how much power those consume
 
Efficiency plays a big part in that number. A 80% efficent PSU will still pull over 1kw from the wall at that load.
 
y2kcamaross said:
I know my buddy with a 2600k/2 7970s pulled over 1000 watts on my killawatt when he loaded up prime95 and furmark
Click to expand...

Power supplies are rated in how much power they will deliver, and indirectly (through 80+) how much they use to deliver it. So killawatt at the wall is an apples to oranges comparison unless you know the efficiency of your friend's PSU. In line with what Jorona was explaining, a 750w unit with 80% would show as pulling 938 watts from the wall to deliver 750w to the system.

If [H]'s review of the 680 is considered, the differential of max draws between the 7970 and the 680 was 12 watts a card in favor of the 680. However, the maximum draw was very dependent upon the game. So, it seems to me that you can probably do it but you will be leaving very little cushion in your power reserve as the PSU ages.
 
There's also the fact that killawatts can be very inaccurate.
 
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