PSU for i7-4790K uATX Machine?? (Plus, what are the specs now??)

[Fun Guy]

I am building a high-performing machine for mostly for graduate school work, using multiple monitors (3). I have a motherboard that should be able to drive all three monitors as there are 3 video outputs on the MB.

Given, that, I was thinking I don't need a huge PSU, right? I mean, this is what I will be powering:

• i7-4790K
• Crucial 256GB SSD (OS and apps)
• WD 6TB HDD (storage)
• MAYBE a discrete video card later, but if so, it will be low-power

So, a 500W piece should suffice, right?? Or maybe a 400W... or a 300W??

Also, I have not bought a PSU in probably 7-8 years, so I have no idea what specs I need. I was using NewEgg's awesome search functionality when I realized I have no clue what standards, certification, etc. I need for this Devil's Canyon PC.

Here is their search page. Eeek!! Can anyone help me on this?

 

[Fun Guy]

NVM...

 

[Fun Guy]

Okay, how do these look??

 

[lehtv]

Out of those, S12II has the best quality components, but its design is a little dated. EA-380D is also good, but Seasonic has longer warranty. Enermax is way overpriced given the fact that it uses CapXon capacitors, and is only a 430 watt unit after all. That Thermaltake just sucks. CX430 is nowhere near cheap enough to be worth buying at $45 - grab it if it's something like $20 after rebate.

None of these is optimal, so let's see what else is available.

Seasonic G360 fits the bill perfectly. $59 after rebate and shipping may sound like much for a 360W unit... but it's only marginally more expensive than the units you linked to, while being better than all of them.

- contains high quality Japanese capacitors (like S12II) but is of newer design than S12II (minor rails filtered from the main +12V rail)
- highly efficient (80+ Gold, same as the Enermax)
- extremely well reviewed and known to put out good quality volts (even beyond its rated wattage) and handle high temperatures with ease (outstanding grades from JonnyGuru, Hardwaresecrets and SPCR, among others)
- uses a ball bearing fan for maximum lifespan

It should very quiet at loads you can expect with a low power discrete card... up to GTX 960, let's say.

 

[Seba]

Okay, how do these look??

For an expensive i7-4790K build you are looking at entry level power supplies?

One good choice would be a Seasonic S12G (non-modular) or Seasonic G Series (semi-modular). But I'll go for a 550W unit (or even a 650W unit, if the prices are close) if there is the possibility to change your mind and add a powerful graphics card later.

 

[buklau]

I have a 400 watt FSP Aurum 80 plus gold, got a 4790k overclocked to 4.8ghz and GTX970 pushed to 1450/7840, been running 100% stable without any issues. So I would say 400 watt shouldn't be a problem.

 

[Fun Guy]

Can you have "too much" power supply? What if a PSU has more than you need, does it use more power than it would if you had a smaller PSU?

For example, if I only need 300W but I buy a 460W, does that 460W PSU use more power "just sitting there" than a 300W? What about a 550W?

Inquiring minds want to know.

 

[MrTeal]

Can you have "too much" power supply? What if a PSU has more than you need, does it use more power than it would if you had a smaller PSU?

For example, if I only need 300W but I buy a 460W, does that 460W PSU use more power "just sitting there" than a 300W? What about a 550W?

Inquiring minds want to know.

Yes and no.
At 300W, a 460W power supply will generally be more efficient than a 300W power supply. Peak efficiency is usually around 50%, so speccing your PSU over the expected DC load will give better efficiency when you're running full out.
OTOH, power supplies tend to run inefficiently at the low end of their range, so if you're idling at 30W, the 300W power supply will likely be more efficient than the 460W.

That's comparing apples to apples though. A 300W Gold supply might be more efficient than a 460W Bronze at both 300W and 30W.

You don't really use more power just because it's a bigger supply though. The efficiency at different levels might be different, but if your computer needs 200W DC, your power supply will pull 10-20% more than that regardless if it's a 300W model or 1000W model. It's not like a 1000W supply would pull 500W to supply 200W.

 

[lehtv]

MrTeal is technically correct that peak efficiency is achieved at around 50% of rated wattage, but in this case it really, really doesn't matter. This build is low enough power that the cost of the power supply itself completely trumps the impact of long term running costs.

edit: Been watching a lot of Daredevil episodes recently, and somehow everything I type sounds like Kingpin in my mind. Scary... D: