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Help me calculate power supply needed. - Page 2

post #11 of 24
Quote:
Originally Posted by icehotshot View Post

A decent 750 watt unit would be much more power than you need, even with massive overclocks.
Many people have no clue what they are talking about, especially with how much power a system needs.
Take a look at this.
http://www.guru3d.com/article/radeon-hd-7970-crossfire-review/7
You would be fine running two overclocked 7970's on a 750 watt psu.
New technology not only increases performance, but it lowers power consumption as well.
Quote to highlight.
850W is plenty for "headroom." Its enough even for SLI 580s, and this card uses less power. The CPU used uses more power as well.

Getting a higher watt unit is your choice though.
Edited by mad0314 - 2/12/12 at 12:13am
    
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post #12 of 24
Thread Starter 
Quote:
Originally Posted by Rainbow Muncher View Post


GPU: ATI 7970 3072MB Gigabyte

.

Heres the 7970 im getting
http://www.itestate.com.au/pages/product/pdt_product_detail.faces?BeanName=productDetailAction&pcode=29488
I think it may be different to the one you are thinking of... Just in case it changes the results of your opinions
Info:
Chipset Radeon HD 7970
Process Technology 28 nm
PCB Form ATX
Core Clock 925 MHz
Memory Clock 5500 MHz
Memory Size 3072 MB
Memory Bus 384 bit
Card Bus PCI-E 3.0
Memory Type GDDR5
DirectX 11
OpenGL 4.2
Multi-view 4
I/O HDMI * 1
DVI-I * 1
Mini DisplayPort *2

Card size H=38 mm, L=285 mm, W=126 mm
Power requirement 550 W
post #13 of 24
Quote:
Originally Posted by mad0314 View Post

lol what? 1K PSU for a single 7970 really?
470
470
Not even a 590 pulls that much. You could easily crossfire on an 850W.

I disagree that you could "easily" crossfire 7970s on an 850w PSU. If you look to overclock your CPU, you'll be cranking its wattage up far past 100w, plus two 7970s at 357w under load, not to mention the extras that you also need to power such as HDDs, optical drives, etc. If you only count CPU and GPU at stock speeds, you'll get power consumption of roughly around 800w. Mind you that's with everything at stock, not including any of the smaller power drainers. If you count on overclocking both your CPU and GPU, depending on how intense your overclock is, you could expect just under 1000w not including any other components (This is going by the graph's overclock @ full load and a CPU overclock of around 4.3ghz @ 1.32v).

So I believe my case still stands: if you don't plan on upgrading any time soon, I would get around a 700-800w PSU, but if you do eventually plan on Crossfiring AND overclocking, get around 1000w. The one thing you should never skimp on in a system is the power supply, and even if your system will run with 2 7970's with a 850w PSU, it will probably not be stable at full load. However, judging a PSU purely on wattage is hugely misleading, since a high quality 700w psu can easily perform as well as a normal-low end 850w one. This is just due to overall build quality and components. I do recommend Corsair for PSU's, they're very popular for gaming systems in most places.

Hope this helped wink.gif
post #14 of 24
Quote:
Originally Posted by theloneplant View Post

I disagree that you could "easily" crossfire 7970s on an 850w PSU. If you look to overclock your CPU, you'll be cranking its wattage up far past 100w, plus two 7970s at 357w under load, not to mention the extras that you also need to power such as HDDs, optical drives, etc.
Hope this helped wink.gif

If you are taking your numbers from the graphs that you quoted, then you are highly mistaken. That is the TOTAL SYSTEM POWER CONSUMPTION. Each 7970 only uses about 200 watts at stock settings, and even with MASSIVE overclocking it would not even be close to 300 watts especially if only overclocking on air.

A corsair/pcpower&cooling/seasonic 750 watt unit would do you just fine even if you decide to get a second 7970 and overclock them both. 850 watt just incase you decide to do something crazy.

People need to back up what they are saying instead of just spitting out false information.

http://www.guru3d.com/article/amd-radeon-hd-7970-review/8

200 watts per card.
Edited by icehotshot - 2/12/12 at 12:31pm
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post #15 of 24
psu calc pro says:

215

settings i used:

high end desktop mobo
i7 2700k @4200MHz 1.4v (100% TDP)
4x DDR3 sticks
1x 6970 (has the same TDP as the 7970)
1x BD-RE/CD/DVD
2x PCI cards
2x PCIEx1 cards
5x 120mm fans
2x 140mm fans

just make sure that the psu you get has enough amperage on the +12v rail. Remember, the key factor is amperage, not wattage.

if you ever plan on getting a second card in the future:

213
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post #16 of 24
650w would be OK right now, maybe bumping right up against the edge if you put a heavy OC on both CPU and GPU, but it will get weaker with time. I'd probably go with a 750w so that in a few years, when it is not quite 750w anymore, it will still be OK.
post #17 of 24
850W unit is all you'll need, my 850w could handle my w3680 @ 4.2 1.35V(or 4.4 @ 1.43V), 2 580s @ 875 clocks 1.1V, full water loop, and lots of other things it will surely work for you. The w3680 is 130W TDP, the 2700k is 95W if I'm correct.
post #18 of 24
Keep in mind the efficiency of the PSU. Shoot for a rating that puts your actual usage in the 50-75% range ie if you expect to use 600w then a 1kw would be "ideal". Most people will tell you that it's overkill but running your PSU at 90% will put the fan on high and generally draw more from the wall. You can get away with less of course but lots of headroom is usually not a bad thing from any perspective other than up front cost of the PSU.
post #19 of 24
^This, what's an extra $40-60 dollars if you'll spend that much a year (maybe like 3/5s even) for running outside the efficiency range, HX1050 lol
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post #20 of 24
Quote:
Originally Posted by Metaldude View Post

Keep in mind the efficiency of the PSU. Shoot for a rating that puts your actual usage in the 50-75% range ie if you expect to use 600w then a 1kw would be "ideal". Most people will tell you that it's overkill but running your PSU at 90% will put the fan on high and generally draw more from the wall. You can get away with less of course but lots of headroom is usually not a bad thing from any perspective other than up front cost of the PSU.

While that is true...I'd rather have the higher efficient in the band of expected normal use... having the highest efficiency for load, if load is only going to occur 5% of the time it's used is pointless if it's less efficient the other 95% of the time.
 
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