PSU consumption in a desktop

[cw2879]

I was watching the excellent Britec video about 'turn your low end PC into a gaming PC' and have the following info which might help anyone considering upgrading

Last year I upgraded my Acer Aspire desktop. I added 4G of RAM, added 2 usb-3.0 ports and a new graphics card (both using PCI) I also changed the drive to SSD and upgraded the processor

I calculated the net result of all of this to be around 20W extra and was wondering if I needed to change the PSU (rated at 220W max). I eneded up not doing so as I reasoned that a desktop manufacturer would need to provide extra capacity in their existing PSU, since they are offering all these empty PCI slots for expansion.

As a check I had one of these devices that plug into 240V mains and display the watts. With all the new gear the desktop seemed to consume around 110W

So it looks as though the spare capacity offered by the PSU is such that under normal conditions this computer was using only half the available power. So in this case the extra 20W caused by the upgrade was easily managable, with no need to change the PSU as well.

Hope this info will help people, or if anyone has similar tales regarding the PSU and upgrades, since it is the only part of a PC upgrade that is a bit of a grey area.

[Timster]

While at idle any power supply will operate a computer with hardware that is rated for higher wattage. The specs of the power supply and the components are rated for what it's capabilities are under 100% load. Out of curiosity try using a program to put your cpu and gpu under a full load while pulling down a large file through your usb 3. Curious to see what load is then.

[cw2879]

Hello Timster,
I did a few checks and here are the results, note that the numbers shown are with the monitor wattage subtracted, power supply max is 220W

Baseline measurement at idle .............. 90W
Two USB3.0 sticks being written to ......95W
Passmark 9.0 Integer test run................97W
Passmark 9.0 DirectX12 3d test run......141W (during mandelbrot test)
Sherlock Holmes game run.....................150W (strolling around London)

I dont think I ever properly stressed out the CPU during this though, not sure about the best program for that

[Timster]

Interesting. Try using HeavyLoad and see what results you get. This program will push your cpu and gpu at 100%

[cw2879]

I think from the attached file my computer is so old it isnt fully able to stress both the GPU and the CPU at the same time. The power measurement was only 120W which means I think it was only stressing the CPU not the GPU. I tried the GPU seperately but it only got to about 35% load befopre the CPU was again at 100%

What was quite interesting was the PC took about 10 mins to switch off, presumably to cool the processor. The first time in 7 years I have seen that behaviour.

Also, if the above is true, it means the CPU will just throttle operations anyway so as far as the orignal question about the PSU is concerned I neednt have bothered worrying about PSU wattage during upgrades as the CPU 'takes care of things' anyway...

FYI this is the device I was using to measure power

https://www.amazon.co.uk/Electricity-230V-250V-Consumption-Analyzer-Protection/dp/B07BGW88Q8

[Timster]

Interesting experiment. Thanks for sharing.

[cw2879]

And great to see Britec give another quality video about the topic.

[Britec]