SUBSIM Radio Room Forums - View Single Post - Graphics card overheating on Aliens vs Predator 3

Arclight · 04-07-11, 10:57 AM

There are huge differences in how PSUs deliver their power. For the earlier example, with 14A on the 12v rail, you only get 168W of the rated 450W.

Now lets look at my previous PSU, a Corsair HX520W. It has 40A on the 12v rail, making 480W of the rated 520 available where it's needed.

My current PSU is a 650W Antec, with 4 12v rails, 2x22A & 2x25A. This PSU is actually capable of delivering it's full, rated 650W on the 12v. (in fact, they could use the same rail system on a 1200W PSU without modifying it)

See the differences? Cheap units simply can't provide the power where you need it. Also, they often lack quality protection, making them more liable to die with a flash and a bang, possibly taking other things along with them.

Anyway, to actually answer your question, normally I'd say 18-20A minimum per rail for any kind of gaming system. But considering the card, it shouldn't give you much trouble.*

One thing to note though, is that you can't exceed the rated Wattage. My current PSU is capable of delivering 1128W on 12v, but the unit is rated for 650W so that's the maximum power it can deliver. It just is extremely unlikely that I'll ever manage to overload any individual rail: that's why they build them with the extra leeway, and that's one of the reasons a good unit is expensive.

*Ah, and that brings me to another point: a lot of multi-rail designs use 1 or more rails for the graphics card(s), while loading everything else on the rail(s) that is left. Have a look at this table: http://www.pcpower.com/technology/power_usage/

So, lets assume 30W for the hard drive, 50W for the board, another 30W for the RAM (2 modules), 80W for the CPU and another 10W for 3 fans. That makes 200W needed on 1 rail, still assuming the graphics card has it own rail and ignoring optical drives, additional hard drives, fans or memory modules.

With that example, that PSU you suggested would fall short. Granted, we're talking peak usage here: the PC should only actually draw that much power when every component works at 100% capacity, which technically never happens. But you really want to be prepared in case it does happen. Also, capacitors age: a PSU will lose power over time. Lastly, a PSU loses efficiency and can start to deliver less stable voltages if you push it to its maximum capacity. Personally I wouldn't advise loading a PSU beyond 80% of its capacity. (that's why people buy big units: keeping the relative load low extends the lifetime of the unit and avoids any issues with unstable voltages due to high loads. No one actually needs 1000-1200W units)

(that is assuming a fairly hefty setup by the way: a fast quad-core, a motherboard with ample features, fast hard drive, etc. Considering it's a slimline tower, power draw would likely fall quite a bit lower than the listings in that table)

edit: I'm only seeing 13A per rail on the unit you linked to.

04-07-11, 10:57 AM	#7
Arclight Navy Seal Join Date: Jun 2008 Location: Land of windmills, tulips, wooden shoes and cheese. Lots of cheese. Posts: 8,467 Downloads: 53 Uploads: 10	There are huge differences in how PSUs deliver their power. For the earlier example, with 14A on the 12v rail, you only get 168W of the rated 450W. Now lets look at my previous PSU, a Corsair HX520W. It has 40A on the 12v rail, making 480W of the rated 520 available where it's needed. My current PSU is a 650W Antec, with 4 12v rails, 2x22A & 2x25A. This PSU is actually capable of delivering it's full, rated 650W on the 12v. (in fact, they could use the same rail system on a 1200W PSU without modifying it) See the differences? Cheap units simply can't provide the power where you need it. Also, they often lack quality protection, making them more liable to die with a flash and a bang, possibly taking other things along with them. Anyway, to actually answer your question, normally I'd say 18-20A minimum per rail for any kind of gaming system. But considering the card, it shouldn't give you much trouble.* One thing to note though, is that you can't exceed the rated Wattage. My current PSU is capable of delivering 1128W on 12v, but the unit is rated for 650W so that's the maximum power it can deliver. It just is extremely unlikely that I'll ever manage to overload any individual rail: that's why they build them with the extra leeway, and that's one of the reasons a good unit is expensive. Ah, and that brings me to another point: a lot of multi-rail designs use 1 or more rails for the graphics card(s), while loading everything else on the rail(s) that is left. Have a look at this table: http://www.pcpower.com/technology/power_usage/ So, lets assume 30W for the hard drive, 50W for the board, another 30W for the RAM (2 modules), 80W for the CPU and another 10W for 3 fans. That makes 200W needed on 1 rail, still assuming the graphics card has it own rail and ignoring optical drives, additional hard drives, fans or memory modules. With that example, that PSU you suggested would fall short. Granted, we're talking peak usage here: the PC should only actually draw that much power when every component works at 100% capacity, which technically never happens. But you really want to be prepared in case it does happen. Also, capacitors age: a PSU will lose power over time. Lastly, a PSU loses efficiency and can start to deliver less stable voltages if you push it to its maximum capacity. Personally I wouldn't advise loading a PSU beyond 80% of its capacity. (that's why people buy big units: keeping the relative load low extends the lifetime of the unit and avoids any issues with unstable voltages due to high loads. No one actually needs* 1000-1200W units) (that is assuming a fairly hefty setup by the way: a fast quad-core, a motherboard with ample features, fast hard drive, etc. Considering it's a slimline tower, power draw would likely fall quite a bit lower than the listings in that table) edit: I'm only seeing 13A per rail on the unit you linked to. __________________ Contritium praecedit superbia. Last edited by Arclight; 04-07-11 at 11:14 AM.