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5870 Crossfire i7 PSU Suggestions?

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December 25, 2009 9:22:45 AM

So I am starting a new build. I am planning on this so far:

G.SKILL 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Triple Channel Kit Desktop Memory Model F3-12800CL8TU-6GBPI - Retail

ASUS EAH5870/2DIS/1GD5/A Radeon HD 5870 (Cypress XT) 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported ... - Retail

COOLER MASTER HAF 932 RC-932-KKN1-GP Black Steel ATX Full Tower Computer Case - Retail

ASUS P6T LGA 1366 Intel X58 ATX Intel Motherboard - Retail

Intel Core i7-920 Bloomfield 2.66GHz LGA 1366 130W Quad-Core Processor Model BX80601920 - Retail

COOLER MASTER Hyper 212 Plus Intel Core i5 & Intel Core i7 compatible RR-B10-212P-G1 120mm "heatpipe direct contact" Long ... - Retail

As well as old parts:

3xSATA
TV Tuner
Sound Card
DVD+-RW
8 USB Devices

I do actually use a lot of these devices at full load often. I watch video on one monitor, while playing a game on the other and my tuner records TV. That pretty much puts everything but 4 of the USB devices into use...

In around a year to a year and a half I plan to OC my i7 to 3.2 - 3.5 and buy another 5870. That is what I want my PSU ready for.

Now I have gotten suggestions anywhere from 700 - 1000 watts. I am guessing I would need closer to 900+ since i usually full load my PC. I honestly do not know though. I have been looking at the Corsair 1000HX but I am not sure if its build setup would work well. It is actually 2x500w built into one...

So if anyone has suggestions on wattage for my system, a specific PSU. Or even knows the rails and voltage required for 2x5870s (I can't find the same answer anywhere...). Thanks.
a c 144 ) Power supply
December 25, 2009 10:04:06 AM

Two 5870's - typical, about 300 watts or 25 amps, peaking to 400 watts or about 34 amps.
Figure about 12 amps max for the CPU.
Four drives - about 3 amps.
Fans - about 2 amps.
That's about 52 amps at 12 volts.

Figure 10 amps at 5 volts max for drive and motherboard logic and 10 amps at 3.3 volts for memory.

That's about 700 watts. Something like a Corsair 750TX with its 60 amp rail would work. But I would use an 850 watt PSU.
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December 25, 2009 10:31:12 AM

Anyone have experience with Enermax Revolution85+ 1050W.

I could currently get it for $185. That is a pretty darn good price for an Enermax PSU with those specs. I mean, thats about how much 850-900 watt PSUs cost if they have the rail requires I need and are not some terrible brand. I have read reviews from some sites that say its good. I seriously might jump on this.
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a c 248 ) Power supply
December 25, 2009 12:42:38 PM

You're in overkill mode. The 1,000 to 1,500 watt power supplies are designed for tri and quad video card configurations. In addition, the new ATI Radeon HD 5000 series of video cards are a little more energy efficient and require less power.

Here are the official ATI power recommendations for the HD Radeon 5870 video card:

PCI Express® based PC is required with one X16 lane graphics slot available on the motherboard

500 watt or greater power supply with two, 75 watt, 6-pin, PCI Express® power connectors

600 watt or greater power supply with four, 6-pin, PCI Express® connectors for ATI CrossFireX™ technology in dual mode.

The recommendations are for an entire pc system.


What do you mean you run your system at full load? The phrase "full load" has several meanings.


Here is a link to a technical review of the Enermax Revolution 85+ 1050 watt power supply:

http://www.jonnyguru.com/modules.php?name=NDReviews&op=...

It is a high quality power supply. It's just a lot more than you actually need.
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December 25, 2009 12:57:53 PM

JohnnyLucky said:
What do you mean you run your system at full load? The phrase "full load" has several meanings.


First, thanks for your post. What I mean by full load is that I actually run all 3 SATA drives, 2 PCI slots, both 5870s and the i7 at around 100%... As I said, I often watch a video, play modern games (Crysis, MW2, Unreal 3 and soon Crysis 2) and record TV at the same time on my PC. I am not positive, as I said I am not familiar with hardware as I am software, but I figured that would pump in more than 750 watts? If you go into the 800 watt range, the prices for a PSU with enough voltage on the rails and a good brand is about $150. if I can get a 1050 watt Enermax for $180 I just figured it would be worth it?

Again, I might be completely stupid. If anything I said doesn't make sense please correct me. As I am sure all of you know way more than me, that's why I am posting here.

PS: Whats the difference between multiple rails? If it has 1 rail with the required voltage, how is that differ ant that 2x rails with pretty much the same voltage as just the 1...?
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a c 248 ) Power supply
December 25, 2009 1:07:20 PM

Compared to the $295.00 sale price at newegg.com it appears to be an excellent bargain considering it is an excellent high quality power supply. Is the price in US dollars? It seems too good to be true.
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