Can an underpowered PSU run safely with computer on idle/non intensive tasks?

Shiracco

Efficiency Noob
Original poster
New User
Nov 24, 2018
5
1
So I am building an S4M system with an R9 Nano and Ryzen 5 1600. The only part i am waiting on is the HDPLEX 400 AC-DC. (Out of stock, no idea when will be available.) However Im really itching to start up my system now. I have a Dell 150w brick from an old Alienware. Assuming I am not running any intensive tasks, could this PSU connected to a HDPLEX 400w DC-ATX run this system safely?
 

cleveland

Master of Cramming
Sep 8, 2016
429
224
could this PSU connected to a HDPLEX 400w DC-ATX run this system safely?
What do you mean with "not running any intensive tasks"? I mean, you have a Ferrari and you're planing to drive 40km/h only?

Also, even without further info about your setup, my guess is that, unless you manage to downclock and undervolt the shit out of your CPU AND GPU, 150w wouldn't be enough.
 

alexs

Chassis Packer
Nov 20, 2018
17
29
The failure mode you should be concerned about is letting the PSU overheat slowly. It may be ok to test-boot the system, but I would not let it run for any prolonged time, and definitely not without supervision. I would not do it blindly either; at the very least, get a power meter and keep an eye on how much it draws.

Laptop PSU is probably the worst possible option wrt overheating.

R9 idles at around 10W. As long as it stays in low power mode, it will likely boot.
That said, if it doesn't go into low power mode immediately at boot for whatever reason, you're hosed.
The rest of the system should idle at around 30..40W but may draw over 100W at full load.

https://www.guru3d.com/articles-pages/amd-ryzen-5-1600-review,7.html <-- some numbers
https://www.tomshardware.com/reviews/amd-radeon-r9-nano,4285-9.html
 
Last edited:

Shiracco

Efficiency Noob
Original poster
New User
Nov 24, 2018
5
1
What do you mean with "not running any intensive tasks"? I mean, you have a Ferrari and you're planing to drive 40km/h only?

Also, even without further info about your setup, my guess is that, unless you manage to downclock and undervolt the shit out of your CPU AND GPU, 150w wouldn't be enough.
As I stated, the PSU i am planning to use is unavailable, I just want to test boot the system mainly. Since none of the components would be at load during boot up, I was wondering if the 150w brick could power this system for that use case.
 

NateDawg72

Master of Cramming
Aug 11, 2016
387
281
just for test booting it should be safe. Shouldn't be powered on long enough or with enough load to overheat it. If the brick has protections built-in then it should just shut off if you pull too much power on boot. More power is drawn at boot than at idle but it shouldn't be an issue since it'll be brief
 

CC Ricers

Shrink Way Wielder
Bronze Supporter
Nov 1, 2015
1,923
2,099
My experience with this is you could avoid doing any GPU intensive tasks and you'd be fine. Web browsing, watching videos, that could be fine. Modern GPUs cap their clocks significantly with lighter usage. But any gaming or GPU rendering would be off limits with the kind of PSU you're using. I assume that's not what you want in the long run, and that you're saving up for a 330W or so down the line to fully use with your setup.

I have a Dell Alienware 150W too and that has shut off protection so you'd know when you hit your limit. When this happens it will cut off the circuit from the wall (the blue ring in the plug will turn off), so you should unplug it from the wall and then plug it back in to use it again.