Power Supply for 4770K and Crossfire 7950

[Smartazz]

Hi all, I just ordered my second Sapphire 7950. I'm planning to rebuild most of my system next month including an i7 4770K and motherboard. I'm going for a high overclock on the CPU and 1100MHz on the GPUs. I'm thinking 850W should be enough to get the job done. I'm willing to spend for quality but I don't want to throw money away. I was thinking about this Seasonic: http://www.newegg.com/Product/Produc...82E16817151108

This computer is strictly for gaming so things like 80 Plus Gold are probably not going to be worth it since this computer won't be on too much. Thanks in advance.

 

[Termie]

I assume you haven't seen this hot deal: http://forums.anandtech.com/showthread.php?t=2318301

Obviously, if you can buy today or tomorrow, it's superior to the Seasonic M12II you linked above.

And yes, 850W is more than enough. You could actually run a highly OC'd dual-7950 system on a quality 750W PSU, but with that deal on the 850W, there's no reason not to get it.

By the way, the newer 7950s may not hit 1100MHz. Perhaps report back on that when you get it.

 

[Smartazz]

Is the X850 substantially quieter than the M12II? If it is, then I'll buy it now.
Edit: I didn't see the promo code. What a deal, I bought it haha. Thanks!

 

[Termie]

Is the X850 substantially quieter than the M12II? If it is, then I'll buy it now.
Edit: I didn't see the promo code. What a deal, I bought it haha. Thanks!

You're welcome!

And yes, it's quieter and more efficient, so it's definitely worth the -$30 you just paid to get it.

 

[toyota]

Hi all, I just ordered my second Sapphire 7950. I'm planning to rebuild most of my system next month including an i7 4770K and motherboard. I'm going for a high overclock on the CPU and 1100MHz on the GPUs. I'm thinking 850W should be enough to get the job done. I'm willing to spend for quality but I don't want to throw money away. I was thinking about this Seasonic: http://www.newegg.com/Product/Produc...82E16817151108

This computer is strictly for gaming so things like 80 Plus Gold are probably not going to be worth it since this computer won't be on too much. Thanks in advance.

lol you could run two highly oced 7950 cards with oced 4770 and still have plenty of room left on a very high quality 850 watt psu. that's especially true with that X-850.

 

[Smartazz]

Since I'm getting this power supply a month before the rest of my build I'm going to test it for coil whine. If it does suffer from bad coil whine, can it be replaced?

 

[cmdrdredd]

Since I'm getting this power supply a month before the rest of my build I'm going to test it for coil whine. If it does suffer from bad coil whine, can it be replaced?

Through newegg you can try to request a refund for it (and hassle with restocking fee nonsense) and buy another one. They may not give you a problem if you claim it's "not working". I don't think they test everything that gets returned. Just don't email or call them and say you have coil whine.

 

[Rvenger]

Through newegg you can try to request a refund for it (and hassle with restocking fee nonsense) and buy another one. They may not give you a problem if you claim it's "not working". I don't think they test everything that gets returned. Just don't email or call them and say you have coil whine.

I told them mine had severe electrical noise and that worked.

 

[cmdrdredd]

I told them mine had severe electrical noise and that worked.

That sounds closer to broken than coil whine to me. Yeah it shouldn't make noise though, if you tell them it's making strange noises when you plug it in they will probably just list it as defective return.

 

[Smartazz]

The enthusiast in me wants to try to water cool these cards. They're very low ASIC scores which I've heard makes for better liquid cooled cards. Is that within the X850 to handle?

 

[MrK6]

The enthusiast in me wants to try to water cool these cards. They're very low ASIC scores which I've heard makes for better liquid cooled cards. Is that within the X850 to handle?

Liquid cooling only requires the extra ~10-20W for a pump. You'll have more than enough room to push your cards to the maximum without hitting 850W. For reference, my system in my signature pulls ~450W from the wall at load, which is about ~400W actual PSU output. Personally I think ASIC scores aren't really indicative of much, however higher leakage chips respond better to voltage and can be pushed further under better cooling.

 

[Smartazz]

One card takes 1.25 volts to hit 1160MHz on air. Does this mean it's a higher leakage chip?

 

[MrK6]

One card takes 1.25 volts to hit 1160MHz on air. Does this mean it's a higher leakage chip?

Not necessarily. Plotting clock speed vs. voltage at a given temperature is a better indicator. In either case, almost any chip will overclock better on better cooling inherently because you're dropping the overall resistance of the chip (linearly though), however some will respond better than others.

 

[Smartazz]

Well I guess I could try, and if it doesn't clock too well it will still be quieter.

 

[Smartazz]

I think two cards are going to cook each other and hurt over clocking. My hypothesis is that the lower temperatures should allow me to lower voltages and/or increase clock speeds.

 

[Elfear]

For reference, with two of my cards at 1300/1650 1.3V and my 2600k@4.95GHz 1.52V, my system pulled around 850W from the wall running the Valley benchmark. I had two other cards idling away so your power consumption would be lower than mine by a bit especially considering the 7950s and Haswell chip.

 

[Smartazz]

For reference, with two of my cards at 1300/1650 1.3V and my 2600k@4.95GHz 1.52V, my system pulled around 850W from the wall running the Valley benchmark. I had two other cards idling away so your power consumption would be lower than mine by a bit especially considering the 7950s and Haswell chip.

I assume all three cards are under water? I'm still weighing out water. For the same price I can get a side panel for a 600t with two 120mm or 140mm. Do they respond much better on water over high end air?

 

[Elfear]

I assume all three cards are under water? I'm still weighing out water. For the same price I can get a side panel for a 600t with two 120mm or 140mm. Do they respond much better on water over high end air?

Three of my cards are under water and the fourth has the stock Dual-X cooler. In my experience, water helps a lot with Tahiti. The only card I really tested the limits for gained an extra 125Mhz on the core going from the reference cooler at 80% fan speed to water.

The best part about watercooling though is the silence. If you get big enough radiators and efficient enough fans, your rig will be very quiet but still dissipate the heat very well. It will cost a bit up front but most of your gear can carry over when you upgrade parts.

I can't comment on the aftermarket air coolers, but I've heard they do a pretty good job.

 

[Smartazz]

Three of my cards are under water and the fourth has the stock Dual-X cooler. In my experience, water helps a lot with Tahiti. The only card I really tested the limits for gained an extra 125Mhz on the core going from the reference cooler at 80% fan speed to water.

The best part about watercooling though is the silence. If you get big enough radiators and efficient enough fans, your rig will be very quiet but still dissipate the heat very well. It will cost a bit up front but most of your gear can carry over when you upgrade parts.

I can't comment on the aftermarket air coolers, but I've heard they do a pretty good job.

Okay thanks. That's very impressive. I could fit three 2x120mm radiators in my case. I hope that I could get these 7950s above 1200MHz. What were the temps at 80% fan speed?

 

[BFG10K]

Moved to PSU forum - Super Moderator BFG10K.

 

[Smartazz]

I got to use my 2nd 7950 today. It runs a bit cooler than the original. I'm seriously reconsidering water cooling them though. They're already ridiculous overkill.

 

[Smartazz]

I have Crossfire running on my current 2500K build and the PSU is cool to the touch when gaming. I haven't overclocked the cards a lot yet, but still an incredible PSU.
Bitcoin mining on both GPUs doesn't even force the fan to spin and it still remains cool to the touch.

 

[Face2Face]

Let us know how PSU does with the 7950's overclocked. It could be my PSU, but with my card clocked @ 1250/1650 playing Crysis 3 my PSU is the loudest fan in the system. The fan sounds like it's maxed out. I need to get a killa-watt and see what type of wattage I am pulling.

 

[Smartazz]

Let us know how PSU does with the 7950's overclocked. It could be my PSU, but with my card clocked @ 1250/1650 playing Crysis 3 my PSU is the loudest fan in the system. The fan sounds like it's maxed out. I need to get a killa-watt and see what type of wattage I am pulling.

My Kill a Watt reports 550 watts while benchmarking. Games are incredibly choppy and I think it's due to a slow 4x PCI-e 1.1 slot, so this might not be indicative of true power use. However, running 3dmark and Unigine I get very good scores so I think I have a good power measurement with those. Both cards are clocked to 1100MHz@1.1 volts and 1400MHz memory. The CPU is a 2500K clocked to 4.5GHz@1.3 volts.

 

[toyota]

4x PCI-e 1.1 slot? I would not even have bothered running a gpu in that slot.