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2 SMPS of a single PC

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  • GPUs
  • Power
  • Graphics
Last response: in Graphics & Displays
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September 4, 2014 12:05:56 PM

Hi people, is it ok to power my PC with 2 diffrent power suplies? Cz, i recently bought a new GPU (ASUS r9 280 DCUT) and I only have a 450 W PSU. I spend all my cash in the GPU and now I really doubt like whether I can use it or not. So was planning to give GPU power from my old 225 W SMPS, while everything else will run in my 450W smps. Is the fine?

More about : smps single

September 4, 2014 12:17:55 PM

Regular PSUs are not designed for load-sharing so having two separate units may cause a wild assortment of issues... particularly in the case of split power with a GPU where part of the power comes from the main PSU through the PCIE x16 slot and more power comes in through the PCIE 6/8-pin connector(s).

Also, your 225W is pretty much certainly not capable of providing 200W on the 12V output while the R9-280 can draw around 250W peak so that idea is definitely busted.

You might be able to power HDDs, DVDs, fans and other loads with fully independent power connections off the 225W PSU but that will only relieve your 450W PSU from something like 30W.

If you connect your 225W PSU's 12V outputs to your 450W PSU's 12V outputs, nobody knows what will happen. There is a slim chance it will work but the more likely outcomes are that either the stronger of the two PSUs will end up providing all the 12V for the whole system and the weaker PSU will simply do nothing or the PSUs will end up in unstable operation, possibly destroy each other and everything they are connected to.

Do not cross the streams. Nobody can predict what will happen if you do.
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September 4, 2014 12:46:30 PM

IIRC correctly there used to be GPU only PSU's sold for just this kind of situation, its not new and quite feasible if done correctly.
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September 4, 2014 12:46:53 PM

InvalidError said:
Regular PSUs are not designed for load-sharing so having two separate units may cause a wild assortment of issues... particularly in the case of split power with a GPU where part of the power comes from the main PSU through the PCIE x16 slot and more power comes in through the PCIE 6/8-pin connector(s).

Also, your 225W is pretty much certainly not capable of providing 200W on the 12V output while the R9-280 can draw around 250W peak so that idea is definitely busted.

You might be able to power HDDs, DVDs, fans and other loads with fully independent power connections off the 225W PSU but that will only relieve your 450W PSU from something like 30W.

If you connect your 225W PSU's 12V outputs to your 450W PSU's 12V outputs, nobody knows what will happen. There is a slim chance it will work but the more likely outcomes are that either the stronger of the two PSUs will end up providing all the 12V for the whole system and the weaker PSU will simply do nothing or the PSUs will end up in unstable operation, possibly destroy each other and everything they are connected to.

Do not cross the streams. Nobody can predict what will happen if you do.


So I really need to wait and buy a new PSU before starting to use that 280, right? Hard luck on me. :(  Anyway, thats for a vry fast replay.. :) 
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September 4, 2014 12:54:04 PM

Mousemonkey said:
IIRC correctly there used to be GPU only PSU's sold for just this kind of situation, its not new and quite feasible if done correctly.


I saw some tutorial in youtube, they where also doing like this. Bt i really dont want to take chances, as if its all get firned, nedd to live without a computer for more that a year.. :D  I wont be able to survive that. Bt even if I have top get a diffrent power supply, then again i need to wait. :(  Totaly in a deadlock. Bt then again in so many places, i say like r9 280 only requires a 500W supply, that why i bought this. Bt in the cover its written like recommended is 750.
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September 4, 2014 1:54:47 PM

Nikhil Das said:
Bt then again in so many places, i say like r9 280 only requires a 500W supply, that why i bought this. Bt in the cover its written like recommended is 750.

The GPU itself needs ~250W peak, the rest of your system should be around 100W for Intel and 150W for AMD so the real power output would be under 400W peak.

If you check the rating labels on your 225W and 450W PSUs though, they might not even reach 400W combined on the 12V output which powers pretty much everything in modern PCs.

To that, you need to add the fact that unless those two are high-quality power supplies, they most likely cannot deliver more than about 70% of their rated output reliably even under ideal circumstances.

Yet another possible issue is that your secondary PSU may not run properly without adequate loads on the otherwise unused 3.3V and 5V rails when the 12V output is heavily loaded.
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September 4, 2014 10:14:20 PM

InvalidError said:
Nikhil Das said:
Bt then again in so many places, i say like r9 280 only requires a 500W supply, that why i bought this. Bt in the cover its written like recommended is 750.

The GPU itself needs ~250W peak, the rest of your system should be around 100W for Intel and 150W for AMD so the real power output would be under 400W peak.

If you check the rating labels on your 225W and 450W PSUs though, they might not even reach 400W combined on the 12V output which powers pretty much everything in modern PCs.

To that, you need to add the fact that unless those two are high-quality power supplies, they most likely cannot deliver more than about 70% of their rated output reliably even under ideal circumstances.

Yet another possible issue is that your secondary PSU may not run properly without adequate loads on the otherwise unused 3.3V and 5V rails when the 12V output is heavily loaded.


Hiii, Thanks for the replay. I decided to wait an buy a 750 Watt, feels like that would be better rather that frying everything.. :D 
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