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Discussion Starter · #1 ·
Hey guys,

I am dreadfully sorry that I have to start a new thread for this, but I am so new to this forum that I am probably breaking a rule with this already.

I am posting my desired build and would like to know what I should realistically consider for a PSU, if you could back up your answers with facts that would be handy:) I have done a lot of research but need to know for my specific needs what should be recommended.

My desired build is as follows:

CPU - Intel Core i7-3770K Quad Core
Motherboard - ASUS Maximus V Formula
Hard Drive - 3TB Seagate Barracuda 7200
Optical Drive - Basic DVD Read/Write (may add a bluray to this later)
Video Card - 2x Radeon HD 7970's
RAM - 16GB 1866MHz G.Skill (probably 4x4)
SSD - Something in the 250GB area
Power Supply - ???
CPU Cooling - Corsair H100i

I also plan to put stupid lights all over it and rice this thing out. I want it to be future proof and the only pieces I've fully committed to already are the dvd drive, the h100i, and the case. Any suggestions whatsoever are welcome, but I am considering a 1000W PSU, odds are I am being rediculous, but I want to keep adding to this thing for a while.

Ultimate goal is to run this thing with 3 monitors, adding a sound card later, and more HDD's for media and such.

Thanks again in advance, and please try to be helpful, if you get on here just to be obnoxious and hate on something I've posted please refrain.
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For this with two 7970s in it, all you need is a quality-made 650W power supply:

http://www.guru3d.com/articles_pages/asus_radeon_hd_7970_crossfire_review,7.html

With two 7970s under full load in their system, their PSU pulled 567W from the wall outlet. Their CPU was idling, so I have to add 150W for a 3770K at 5 GHz under full load. So adding 150W to 567W makes the PSU pulling 717W from the wall outlet, and so if the PSU is 85% efficient while pulling 717W from the wall outlet, then the system is pulling 609W from the PSU. This is unrealistically high because I'm saying the 7970s and the 3770K are completely maxed out simultaneously, plus I'm saying the 3770K is at 5 GHz and pulling 150W. Your actual gaming load will be about 500-525W on average. Therefore, a quality-made 650W would keep your average power draw right in the sweet spot which maximizes your PSU's efficiency.
 

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Discussion Starter · #3 ·
Another question I have to add:
If I do decide to be over the top and get a 850-1000w, are there any downsides to that? I feel like you can never have too much power, but obviously, I can be wrong, this is my first personal build and I just want to make sure I do everything right:
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Quote:
Originally Posted by Colorful Dan View Post

Another question I have to add:
If I do decide to be over the top and get a 850-1000w, are there any downsides to that? I feel like you can never have too much power, but obviously, I can be wrong, this is my first personal build and I just want to make sure I do everything right:
thumb.gif
The only downside is that you're wasting money on something that won't benefit you at all.
 

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Quote:
Originally Posted by Colorful Dan View Post

Another question I have to add:
If I do decide to be over the top and get a 850-1000w, are there any downsides to that? I feel like you can never have too much power, but obviously, I can be wrong, this is my first personal build and I just want to make sure I do everything right:
thumb.gif
Yep: it's a waste of money. ;) Or, you could end up having to settle for a lower-quality unit in order to avoid spending more than you otherwise would with a very nice 650W power supply.

If you're concerned about future upgrades, then don't be unless you plan on adding a third 7970 or having three top-of-the-line video cards some day. I mean, each new generation of GPUs and CPUs requires less power than the previous, so getting a quality-made 650W should last "forever".

If you plan on heavily overclocking the 7970s and even increasing their voltages quite a bit, then maybe get a nice 750W PSU, but that wouldn't really be the minimum.

Can you order from Newegg.com?
 

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Quote:
Originally Posted by Colorful Dan View Post

Another question I have to add:
If I do decide to be over the top and get a 850-1000w, are there any downsides to that? I feel like you can never have too much power, but obviously, I can be wrong, this is my first personal build and I just want to make sure I do everything right:
thumb.gif
Quote:
Originally Posted by AndyM95 View Post

Quote:
Originally Posted by Colorful Dan View Post

Another question I have to add:
If I do decide to be over the top and get a 850-1000w, are there any downsides to that? I feel like you can never have too much power, but obviously, I can be wrong, this is my first personal build and I just want to make sure I do everything right:
thumb.gif
The only downside is that you're wasting money on something that won't benefit you at all.
Well, you should know PSU's are the most efficient at around 50% load. So if most of the time your PSU is at 50% load, then you have the right PSU. There is no bad thing for having a bit of head room.

Personally, I would say a 750 or 850w PSU.
 

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Quote:
Originally Posted by AndyM95 View Post

The only downside is that you're wasting money on something that won't benefit you at all.
There are several upsides too. First, you can have upgrade flexibility. Second, your PSU will run cooler with more headroom which means less fan noise. Third, PSU typically have maximum efficiency at 50% load. So 850W PSU is likely to save your power bill a bit.
 

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Quote:
Originally Posted by Colorful Dan View Post

Another question I have to add:
If I do decide to be over the top and get a 850-1000w, are there any downsides to that? I feel like you can never have too much power, but obviously, I can be wrong, this is my first personal build and I just want to make sure I do everything right:
thumb.gif
As side from the money spent that was not needed to be.

going with two cables estimation of ~500w pull while gaming
PSUs are not intended to be very efficient at 50% draw (assuming a 1000w PSU) so your power bill might take a hit using a PSU in such an inefficient way
Quote:
Originally Posted by Whalemeal View Post

There are several upsides too. First, you can have upgrade flexibility. Second, your PSU will run cooler with more headroom which means less fan noise. Third, PSU typically have maximum efficiency at 50% load. So 850W PSU is likely to save your power bill a bit.
this use to be true(40%-60%), however now its usually 80+ (which is why we have 80+ ratings) assuming a quality build PSU, which is pretty much the most important part of your build. (its the heart if you will)
 

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Quote:
Originally Posted by TwoCables View Post

No.

On PSU Efficiency

PSU "50% Load" Myth
Well that seems like an awful averaging of efficiencies lol. Taking arithmetic average for possible load scenarios? Efficiencies should be weighted by the power draw. You should care less about efficiency at idle and more about efficiency at full load. After all, it's your power bill that matters.
 

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Damn, you guys are speed readers. It took me a LOT longer to read both of those articles than it took you guys. I'm jealous.

Quote:
Originally Posted by AndyM95 View Post

^^^ With good, modern PSUs they are still about 90% efficient even at full load.
I've found that most people want the efficiency that was advertised because most people are basing their purchase on the 80+ Certification (which I recommend not doing, but hey).

Quote:
Originally Posted by Whalemeal View Post

Well that seems like an awful averaging of efficiencies lol. Taking arithmetic average for possible load scenarios? Efficiencies should be weighted by the power draw. You should care less about efficiency at idle and more about efficiency at full load. After all, it's your power bill that matters.
This is about the average power draw. If your maximum power draw is 500W, then are you going to buy a 1000W PSU just so your maximum power draw is 50% of your PSUs capacity?
 

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Quote:
Originally Posted by TwoCables View Post

Damn, you guys are speed readers. It took me a LOT longer to read both of those articles than it took you guys. I'm jealous.

I've found that most people want the efficiency that was advertised because most people are basing their purchase on the 80+ Certification (which I recommend not doing, but hey).

This is about the average power draw. If your maximum power draw is 500W, then are you going to buy a 1000W PSU just so your maximum power draw is 50% of your PSUs capacity?
No. But I would buy a PSU that can run my gaming power draw at 50~60% power. In OP's setup I estimate that will be around 400W+.So I recommend him to get at least 750W+. You should definitely weight more on the scenario where you use your computer most intensively.
 

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Quote:
Originally Posted by Whalemeal View Post

No. But I would buy a PSU that can run my gaming power draw at 50~60% power. In OP's setup I estimate that will be around 400W+.So I recommend him to get at least 750W+. You should definitely weight more on the scenario where you use your computer most intensively.
Well, if the only thing the computer is used for is gaming from the moment it's turned on to the moment it's turned off, then the average load can be determined mostly by that - but not entirely because there's still e-mail, internet, OCN (lol yeah, I separated internet and OCN), etc. If the computer is left on 24/7 and is idling when it's not in use, then the gaming is nowhere near being the average load.

His gaming load will max out at about 500-525W. Any quality-made 650W power supply would be just fine for this because the kind of PSU he'll end up with is one that can easily deliver 650W continuously if it's ever needed. I'm not going to recommend anything 'bigger' than that because it's just not needed at all. Let's say that you need a bucket for exactly 5 gallons because that's the most you'll ever put in it. Let's say that good 5 gallon buckets can actually hold about 7-8 gallons if you fill them to the very top. This means you can carry those 5 gallons around without spilling and it also leaves you with lots of room for water displacement. So, there's no need to get a bucket that has a larger capacity because your quality-made bucket can hold more than 5 gallons so that you can carry it around comfortably without any problems and you can displace water any time you need to without it flowing over the top.

I know, that was not the greatest analogy, but it was all I had in my mind for some reason.
 

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Quote:
Originally Posted by TwoCables View Post

Well, if the only thing the computer is used for is gaming from the moment it's turned on to the moment it's turned off, then the average load can be determined mostly by that - but not entirely because there's still e-mail, internet, OCN (lol yeah, I separated internet and OCN), etc. If the computer is left on 24/7 and is idling when it's not in use, then the gaming is nowhere near being the average load.

His gaming load will max out at about 500-525W. Any quality-made 650W power supply would be just fine for this because the kind of PSU he'll end up with is one that can easily deliver 650W continuously if it's ever needed. I'm not going to recommend anything 'bigger' than that because it's just not needed at all. Let's say that you need a bucket for exactly 5 gallons because that's the most you'll ever put in it. Let's say that good 5 gallon buckets can actually hold about 7-8 gallons if you fill them to the very top. This means you can carry those 5 gallons around without spilling and it also leaves you with lots of room for water displacement. So, there's no need to get a bucket that has a larger capacity because your quality-made bucket can hold more than 5 gallons so that you can carry it around comfortably without any problems and you can displace water any time you need to without it flowing over the top.

I know, that was not the greatest analogy, but it was all I had in my mind for some reason.
Well I agree that 650W is cost efficient for hist setup. But the calculation in the article you pointed is just wrong. If you calculate the actual energy that is wasted in air with a given usage scenario, you will find that 650W will give less number albeit not enough to justify the price difference between two PSUs. Even though you turn on your computer 24/7 and play games for like 3 hours, the energy wasted in air is probably more from gaming.
 

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Quote:
Originally Posted by Whalemeal View Post

Well I agree that 650W is cost efficient for hist setup. But the calculation in the article you pointed is just wrong. If you calculate the actual energy that is wasted in air with a given usage scenario, you will find that 650W will give less number albeit not enough to justify the price difference between two PSUs. Even though you turn on your computer 24/7 and play games for like 3 hours, the energy wasted in air is probably more from gaming.
How is it wrong? What part is wrong? I don't know see what's incorrect. They measured the power draw at the wall outlet with the 7970s maxed out, their CPU was idling, so I added 150W to that. Then I multiplied that value by .85 for 85% efficiency because their test PSU is about 85% efficient, and so that's the power that the system would be pulling from the PSU in such an extreme situation. The actual gaming load is lower, at about 500-525W tops. Then you take a quality-made 650W than can easily deliver 650W non-stop, and these power draws are easy for it. It would be a complete waste of money to get a 750W PSU unless the 7970s are to be heavily overclocked along with the 3770K. So, I'm waiting to find out if Dan will be overclocking his 7970s.
 

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Quote:
Originally Posted by TwoCables View Post

How is it wrong? What part is wrong? I don't know see what's incorrect. They measured the power draw at the wall outlet with the 7970s maxed out, their CPU was idling, so I added 150W to that. Then I multiplied that value by .85 for 85% efficiency because their test PSU is about 85% efficient, and so that's the power that the system would be pulling from the PSU in such an extreme situation. The actual gaming load is lower, at about 500-525W tops. Then you take a quality-made 650W than can easily deliver 650W non-stop, and these power draws are easy for it. It would be a complete waste of money to get a 750W PSU unless the 7970s are to be heavily overclocked along with the 3770K. So, I'm waiting to find out if Dan will be overclocking his 7970s.
I'm talking about the article titled PSU "50% Load" Myth that talks bout 650W vs 400W. Let me be a math nerd here. Let u(x) be your usage scenario at x Watt of load that integrates to 24 hours. Let e(x) be the efficiency curve of a power supply. Then the average efficiency you should care about is integral of u(x)*x*e(x) over 0 to max draw. However the article says that average efficiency is integral of u(x)*e(x) (well even cruder than that but the spirit is the same).
 

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Discussion Starter · #19 ·
Quote:
Originally Posted by TwoCables View Post

So, I'm waiting to find out if Dan will be overclocking his 7970s.
Hey, sorry, I'm back, I was out to lunch, so many responses! my plan is to game with this obv, but yes I will be overclocking, I am going to get as much out of this as possible, and to touch on my purchasing abilities, yes Newegg is possible, I live in the US. This sounds Like I want an 850, just so I can be happy that I will be ready for the future and because having more makes me happy. So would anyone like to help me on which of the 850's is the best to have? again with using facts and personal experience please:)

(Side note: there are so many different makers/versions of the Radeon HD 7970...does it matter who I go with? also, I am going with a red theme on my case if that helps with decisions)

Two Cables, you are being very helpful, and thank you for that!
 

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Ah the mystical 50% load for greatest efficiency Unicorn

A good quality Bronze rated unit wil have a 3% or lower swing in efficiency between 20-100% load
Gold will get you in the 1.5% area

Who thinks it matters ?
 
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