# Please recommend a good power supply for this new PC build

1. Mar 9, 2013

### Kutt

Please recommend a high quality power supply (at least 1KW) for this new gaming build. I haven't finished it yet, but it should be complete within the next few months..

*Core i7 3770K
*Corsair Dominator Platinum 8GB DDR3 1600MHz cl9 RAM
*MSI Big Bang Mpower Z77 motherboard
*Two-way SLI GTX 680 MSI Lightning graphics cards
*Western Digital 1TB 7200RPM HDD
*Corsair Vengeance C70 mid-tower case
*Corsair H100i liquid CPU cooling
*24x speed DVD ROM

2. Mar 9, 2013

### pantaz

I've had good luck with Corsair and Antec.

3. Mar 11, 2013

### Routaran

CORSAIR Professional Series Gold AX1200 (CMPSU-1200AX) 1200W

4. Mar 11, 2013

### Kutt

1200W is excessive for two GTX 680's in SLI

1000W is sufficient.

5. Mar 12, 2013

### Routaran

6. Mar 14, 2013

### Cod

You don't need an 1000W PSU. You could easily use a quality 750W PSU. Quality / Efficiency is the most important thing when dealing with PSUs. An efficient 750W PSU will outperform a standard (or budget) 1000W PSU.

With that said, for your build, I'd go with this SeaSonic 850: https://www.amazon.com/Seasonic-ATX...=UTF8&qid=1363257285&sr=8-2&keywords=SeaSonic. Little expensive, but will last a very long time and give you some overhead for overclocking and future upgrades.

Last edited by a moderator: May 6, 2017
7. Mar 14, 2013

### Kutt

http://www.hardwareheaven.com/revie...digital-power-supply-review-introduction.html

Last edited by a moderator: May 6, 2017
8. Mar 15, 2013

### Cod

I've never looked in the \$200+ price range, so I've never come across this one. Everything looks great in regards to the rails, quietness, etc.. Overall looks like a solid, efficient PSU with enough power to easily power your planned system.

BTW, check out JonnyGuru. The site is dedicated to PSUs. Tons of informative information.

Last edited by a moderator: May 6, 2017
9. Mar 15, 2013

### Kutt

Do I really need a 1000W for a dual SLI GTX 680 system? Each GTX 680 uses only 195 watts at 100% load.

10. Mar 15, 2013

### FastWing

Kutt, each 680 needs 176 watts on 12V rail at max 3d draw during gaming. In rare and unlikely scenarios, it might jump up to 210 watts.

Just to be safe, lets say that both video cards draw 420 watts total on the 12V rail. Your CPU also needs 130-150 watts on the 12V rail.

So get a 570 or 550 watt (on the 12V rail) power supply or 600 if you round up. I wouldn't go any lower than 500. Recall that if you buy a multi-rail PSU, then it becomes more complicated. Let me know if you buy a multi-rail PSU and I'll help you.

Sources: http://www.anandtech.com/show/5771/the-intel-ivy-bridge-core-i7-3770k-review/20
http://forums.atomicmpc.com.au/index.php?showtopic=264

11. Mar 16, 2013

### Kutt

Which is better for high-end systems? Single or multi-rail?

12. Mar 16, 2013

### FastWing

Single-rail puts all 12V load on a single rail. Multi-rail has multiple rails so it splits up the load over multiple 12V rails.

Single-rail

Diagram: http://www.thermaltakeusa.com/ProductHtml/image/W0319RU/outputTable.jpg

To calculate the theoretical number of watts on the 12V rail for single-rail:

$$P_{ 12V }=VI\\ P_{ 12V }=(12V)(69A)\\ P_{ 12V }=828\quad watts$$

So as you can see, even though it is a 850 watt PSU, it can only do up to 828 watts on the 12V rail.

Multi-rail

Diagram: http://www.legitreviews.com/images/reviews/348/ocz700_label.jpg

To calculate the theoretical number of watts on the 12V rail for multi-rail:

$$P_{ 12V }=V{ I }_{ 1 }+V{ I }_{ 2 }+V{ I }_{ 3 }+V{ I }_{ 4 }\\ P_{ 12V }=(12V)(18A)+(12V)(18A)+(12V)(18A)+(12V)(18A)\\ P_{ 12V }=864\quad watts$$

In the chart, however, it says that the maximum combined power for all 4 12V rails is 680 watts. The actual 12V wattage of 680 watts is lower than the theoretical 12V wattage of 864 watts because this PSU can't do full load on all four rails all at once. Once again, even though it is a 700 watt PSU, it can only do 680 watts on 12V. Both single-rail PSUs and multi-rail PSUs (assuming the PSUs are decent) have actual 12V wattage on their charts (in contrast to relying on calculated theoreticals).

The reason why single-rail is better is because it doesn't matter how you wire up your computer - you're guaranteed to get the power on the diagram. If you have 16 12V wires on a single-rail PSU, all 12V wires hook up to the same rail. However, if you have 16 12V wires on a 4-rail PSU, then 4 12V wires go to each rail. If you hook up your computer using all 4 wires that come from the same rail in a multi-rail PSU, then you might end up overloading the rail because each rail can only do a fraction of the combined rails. Example: the single-rail PSU given as an example earlier can do up to 69A on its only rail. However, the multi-rail PSU can only do up to 18A only any given rail.

Assuming that both conditions below are satisfied, then both single-rail and multi-rail PSUs offer the same performance on 12V:

(i) the multi-rail PSU is hooked up properly.
(ii) both PSUs over the same watts on the 12V rail.

Last edited: Mar 16, 2013
13. Mar 16, 2013

### FastWing

Also, if you're interested in electronics, I recommend:

(i) overclock.net for the practical side
(ii) allaboutcircuits.com for the theoretical side

14. Mar 16, 2013

### Kutt

Could you recommend a good quality single-rail PSU that would power the following system?

Core i7 3770K
16GB DDR3 1600MHz RAM
Dual SLI GTX 680
MSI Big Bang Mpower Z77 motherboard

15. Mar 16, 2013

### FastWing

What stores are you buying from? Provide the stores' websites.

16. Mar 16, 2013

### Kutt

Fry's electronics and newegg.com

I bought most of my hardware from my local electronics retailer, but there are a few items which they do not carry in-store and had to order off the internet.

I am quite impressed by the quality, convenience, and fast delivery times of newegg.com, I ordered 2.1 speakers and a 16GB memory kit from them and they arrived at my doorstep within a few days.

All I have left to buy is the power supply, the corsair h100i CPU liquid cooler, the operating system, and anti-virus software, and then I'm ready to put it together!

Last edited: Mar 16, 2013
17. Mar 20, 2013

### Routaran

Multi-rail vs Single rail really doesn't matter with respect to power or performance of a system. What they do impact is the safety and protection from damage in case of a power surge or a short circuit.

Rails are a group of wires that the PSU monitors, (I think its called OCP-Over Current Protection)keeps track of how much current is flowing and shuts down the PSU if it exceeds a certain threshold.

On single rail PSU's, all the wires are monitored as a single unit so the current limit is usually high, like 40A-45A because the PSU is monitoring total usage. So if there is a short circuit on say the 12V line, then the current flow will increase in the 12v line till the overall flow is high enough and the cut off point is reached. Because the cut off point is so high, generally this means that something will probably burn (mobo, PSU, whatever) before the cut off point is reached.

On a multi rail PSU, the groups of wires are monitored separately. This allows different components to be on different rails. The cutoff value is lower for each rail so the system components are safer. For example, the CPU on one rail, the graphics cards on another rail etc. So you can drop the cutoff current down to say 20-25A, shutdown the PSU before damage is done to components.

For power supplies rated 550W or lower, 550W/12v = apprx 45A so the cutoff for the rail might be around 40A or so. You won't pull more than that before overloading the power supply so it doesn't matter if you have a single rail or multi rail. There's really no difference.

For power supplies 650W and over there is a marginal benefit to having multi-rail because of the added protection it provides. For PSUs around 1000W or higher, you want to have multi rail because if there is any short circuit in a single rail PSU, you will be pushing a lot of amps and its most likely to fry something.

But there is absolutely no difference in performance. Power is power. 850W from a single rail is the same as 850W from multi rail.

18. Mar 21, 2013

### Chronos

A good way to pick a power supply is to double the current draw of all your components. A PSU is a terrible way to cheap your system build.