wizardofid
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Choosing a PSU for a gaming rig, is not a daunting task but is one of the most important aspect of a gaming rig. To choose the correct one, you need to look at the 12 volt output of the PSU. The 5volt and 3.3volt rails is of little importance as you generally don’t run into problems there, as the hardware that use those rails are low wattage unless you start adding a lot of hard drives or water cooling equipment . I dislike the use of PSU calculators, I prefer not to use them, as it adds little or no info really needed to make an informed choice about the actual wattage needed in a PSU.
The total wattage that these PSU calculators gives you means squat, as it combines the totals for all the rails, 3.3volt 5volt and 12volt, and really it’s just rubbish to use them. Don’t use them the 12volt rail is more important if you have a 12volt heavy rig and 5volt more important in a 5 volt heavy rig. The 12volt rail(s) is all that should concern you for building a gaming rig with dual or single GPU’s. Now contrary to popular believe hardware power usage has actually gone down not up, so you don’t really need that massive PSU you think you might need, albeit some overhead is never bad, but buying a 1500watt PSU for running a i3 and dual 7770′s is a waste, if the price is right there is no risk involved, the high end high wattage units do now and then have efficiency issues at low loads.
The easiest way to find out what PSU you need, is to add the max output wattage of the 12volt hardware, most importantly CPU(s) and GPU(s) together, I am not considering, WC and other cooling solutions as it differs from system to system, a quick google search will show the max power output of the cooling options without too much effort. Example : I have a 2500K and 2 x 580GTX’s max power output for the 2500K is 95watts and 255 watts +- a card, total wattage is 605watts. If you want a more complete total you can add all the 12volt wattage requirements together and divide by 12 to give the amp requirement. I only consider these two items for PSU selection as they use the most power in any system, and often the two hardware items that will actually push their max output on a peak basis, meaning the output isn’t continual but rather, much like a heart rate monitor if I can use that as a example.
This may sound a bit Greek but often you will find units that have a peak and a continual rating on the PSU label or manual, what you should concern your self with is the continual rated output this should meet your PSU requirement, peak rating is basically the amount of wattage a PSU can push out for a short period of time, where continual rated wattage is the amount it can push out on a constant basis, usually a PSU will be rated based on the continual rated wattage, but there are some OEM’s and brands that lies about this, or just completely omit the info. Now we already figured out that if and when the system needs to pull max power we will need at least a 605watts.Divide that total, by 12 will give you the amount of amps needed you will need a min of 50amps on the 12volt rail(s) excluding the rest of the hardware, but honestly standard hardware like mboard, mouse, keyboard and 5 HDD’s, 5 fans wouldn’t pull more than +-120watts, if at all that much.
To be on the safe side just add another 250 watts on top of CPU and GPU requirement, for additional hardware and a little headroom for upgrades and the likes. Now for our complete gaming rig a 850 watt PSU will do the trick.Take note your system is likely to use less than this, but I consider a PSU at 50% load is better than a PSU and 95% load, especially when you start applying heat, things tend to go a little pear shape. A PSU derates about 5 to 10 watts per degree increase over the threshold of the rated temp at which the PSU can supply the rated continual wattage. Summer times are not kind to PSU’s 55, 60 odd degrees shouldn’t be a surprise, keep that in mind. As for single rail or multi rail makes ZERO impact contrary to what you have been told, single rail is just easier to work with you don’t have to worry about load balancing, and that is all that is to it.Single rail PSU’s are really only a danger when working with really high wattage units.A single rail PSU doesn’t overclock better than a multi rail PSU either.
So choose what ever rail you want, makes no difference as to how the hardware gets it’s power the end.The marketing behind single or multi rail PSU’s is really just as annoying, just ignore it, nothing special about it. A final note as mentioned a PSU, may say total output is 850 watts, remember that is often the combined rail outputs and might not actually tell you what you really need so you would need to read the PSU label. If the requirement on the 12volt rail in worst case scenario is 850 watts you need to confirm the rail or rails on the 12 volt is able to push a continual 850watts, excluding the 3.3volt and 5volt rails. Also remember even if that PSU states it has 4 rails with 36 amps per rail you can’t add the rails together for total output as the rails information is the max that specific rail can output, the rails is fed by a single pool, so if you have a total of 850watts in the pool, each rail can pull max together 17 amps, but not all rails will pull the same amount of power, which is why CPU and GPU often have rails that have higher amp output, than the rest of the rails. This is where load balancing comes in, and where you need to make sure you don’t over load a rail. All you need to do is decide which PSU you want now. There is at least a dozen goods brand out there all with unique designs and features. The following PSU series are all tried and tested for gaming : Corsair HX series 2013 Corsair AX 2013 and AXi series Coolermaster V Series 2013, Be Quite Dark series, Antec HCP, Antec HCG , XFX Core Edition Series Seasonic, Zippy/Emac Flectronic and PCP&C.
The total wattage that these PSU calculators gives you means squat, as it combines the totals for all the rails, 3.3volt 5volt and 12volt, and really it’s just rubbish to use them. Don’t use them the 12volt rail is more important if you have a 12volt heavy rig and 5volt more important in a 5 volt heavy rig. The 12volt rail(s) is all that should concern you for building a gaming rig with dual or single GPU’s. Now contrary to popular believe hardware power usage has actually gone down not up, so you don’t really need that massive PSU you think you might need, albeit some overhead is never bad, but buying a 1500watt PSU for running a i3 and dual 7770′s is a waste, if the price is right there is no risk involved, the high end high wattage units do now and then have efficiency issues at low loads.
The easiest way to find out what PSU you need, is to add the max output wattage of the 12volt hardware, most importantly CPU(s) and GPU(s) together, I am not considering, WC and other cooling solutions as it differs from system to system, a quick google search will show the max power output of the cooling options without too much effort. Example : I have a 2500K and 2 x 580GTX’s max power output for the 2500K is 95watts and 255 watts +- a card, total wattage is 605watts. If you want a more complete total you can add all the 12volt wattage requirements together and divide by 12 to give the amp requirement. I only consider these two items for PSU selection as they use the most power in any system, and often the two hardware items that will actually push their max output on a peak basis, meaning the output isn’t continual but rather, much like a heart rate monitor if I can use that as a example.
This may sound a bit Greek but often you will find units that have a peak and a continual rating on the PSU label or manual, what you should concern your self with is the continual rated output this should meet your PSU requirement, peak rating is basically the amount of wattage a PSU can push out for a short period of time, where continual rated wattage is the amount it can push out on a constant basis, usually a PSU will be rated based on the continual rated wattage, but there are some OEM’s and brands that lies about this, or just completely omit the info. Now we already figured out that if and when the system needs to pull max power we will need at least a 605watts.Divide that total, by 12 will give you the amount of amps needed you will need a min of 50amps on the 12volt rail(s) excluding the rest of the hardware, but honestly standard hardware like mboard, mouse, keyboard and 5 HDD’s, 5 fans wouldn’t pull more than +-120watts, if at all that much.
To be on the safe side just add another 250 watts on top of CPU and GPU requirement, for additional hardware and a little headroom for upgrades and the likes. Now for our complete gaming rig a 850 watt PSU will do the trick.Take note your system is likely to use less than this, but I consider a PSU at 50% load is better than a PSU and 95% load, especially when you start applying heat, things tend to go a little pear shape. A PSU derates about 5 to 10 watts per degree increase over the threshold of the rated temp at which the PSU can supply the rated continual wattage. Summer times are not kind to PSU’s 55, 60 odd degrees shouldn’t be a surprise, keep that in mind. As for single rail or multi rail makes ZERO impact contrary to what you have been told, single rail is just easier to work with you don’t have to worry about load balancing, and that is all that is to it.Single rail PSU’s are really only a danger when working with really high wattage units.A single rail PSU doesn’t overclock better than a multi rail PSU either.
So choose what ever rail you want, makes no difference as to how the hardware gets it’s power the end.The marketing behind single or multi rail PSU’s is really just as annoying, just ignore it, nothing special about it. A final note as mentioned a PSU, may say total output is 850 watts, remember that is often the combined rail outputs and might not actually tell you what you really need so you would need to read the PSU label. If the requirement on the 12volt rail in worst case scenario is 850 watts you need to confirm the rail or rails on the 12 volt is able to push a continual 850watts, excluding the 3.3volt and 5volt rails. Also remember even if that PSU states it has 4 rails with 36 amps per rail you can’t add the rails together for total output as the rails information is the max that specific rail can output, the rails is fed by a single pool, so if you have a total of 850watts in the pool, each rail can pull max together 17 amps, but not all rails will pull the same amount of power, which is why CPU and GPU often have rails that have higher amp output, than the rest of the rails. This is where load balancing comes in, and where you need to make sure you don’t over load a rail. All you need to do is decide which PSU you want now. There is at least a dozen goods brand out there all with unique designs and features. The following PSU series are all tried and tested for gaming : Corsair HX series 2013 Corsair AX 2013 and AXi series Coolermaster V Series 2013, Be Quite Dark series, Antec HCP, Antec HCG , XFX Core Edition Series Seasonic, Zippy/Emac Flectronic and PCP&C.
Yeah can't go wrong with seasonic the are just awesome. X series no different, perhaps not the best looker 
