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How to check underpower?


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I have a PC about 5 years old with a 450W PSU. I've been using the onboard Intel graphics, but concerned that the video socket may be damaged. I have a video card I'd like to try as a backup.

I don't want to overstretch the PSU. If it is drawing too much,, how would that show? Just suddenly dead screen?

What is a good way to estimate power consumption? Tools like HWmonitor show temperatures and voltages, but not power.



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Recent (like in the last 10-15 years) ATX PSU's have generally short circuit and overdraw/overcurrent protection, i.e. if you draw too much power they will simply switch off, but it is not necessarily true, el-cheapo, no-name PSU's may well lack this form of protection, though it would be an exception.

And there is no way to know[1] for sure.

Additionally, there is no easy/cheap device to actually test a PSU behaviour under load, all the testers that you can find are essentially multi-channel voltmeters, they are used to verify that a PSU is providing voltages within specs without load (or with a minimal one), what would be needed is a series of shunts or an electronic load, such devices can be found for several hundreds of dollars at a minimum and, given the high amount of Amps (or Watts if you prefer) involved you would need particularly beefy ones.

There are many "PSU calculators" available but the results they provide (given that your hardware is listed on them) are - in the best case -  a vague approximation of the real power needed, and - on the other hand - a PSU. particularly if old/used may well still work fine with a lower load but fail if too much Amperes are required by the motherboard or devices.

As well, there is software that can check load/power but it depends on sensors that your specific hardware may or may not have


A better approximation would be using a surely powerful enough PSU with the actual hardware, first checking how much the PSU draws form mains socket and then with an amperometer/multimeter how many amperes are drawn on each rail.

It is anyway a lot of work, not worth it (IMHO) unless you are trying to optimize a build for some particular reason.

Try estimating the needed power via one or two of the online calculators, and if the result seems roughly compatible with your PSU, try it, if it overdraws current in 95% or 99% of cases the protection will kick in and switch it off without damage, in the remainling 1%-5% it will release the magic smoke and you will have to buy a new (more powerful) PSU (which you would need anyway, the differnce would be only about having an old spare working 450W PSU or not).


[1] you could - in theory - put a fuse on each voltage line/rail

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