Question Can I use 2 12v rails from secondary PSU and a 12v rail from the one for motherboard to make a 8 pin connector?

[ChrisWaters]

I have a PSU for motherboard and a secondary PSU for GPU. Can I use 2 12v rails from separate PSUs? I know I'm going to get ridiculed for this question

 

[Grobe]

Can I use 2 12v rails from separate PSUs?

In theory, yes. But you must make sure you have a common 0V (not same as chassis ground) and you must pick which PSU to use as primary and the other used as secondary.

Here is a relevant article on the topic you need to read:

Can You Use Two Power Supplies With One Computer?

Prepare for trouble; make it double.

www.howtogeek.com

 

[--SID--]

First question is why?
What's the brand and model of the PSUs?
What motherboard and CPU?

 

[USAFRet]

I have a PSU for motherboard and a secondary PSU for GPU. Can I use 2 12v rails from separate PSUs? I know I'm going to get ridiculed for this question

If you wish to release the magic smoke from one or more of your components, sure.

Is it possible?
Yes.

Is it recommended?
No.

Asking "Can I?" leads into the magic smoke comment.

What components are involved here? Make/model of everything.

 

[ChrisWaters]

Hp pro elite desk 800 g1 SFF
Intel I-5 4570
Hp 1998 motherboard
1-240w PSU and 1-bestec 250w
Gigabyte Radeon AMD Rx 580(was going to use 250w here)
I was wondering if it's alright to have 2 grounds and one 12v from 240w and 3 grounds and 2 12v from the 240w to make a 8pin for gpu

 

[USAFRet]

1-240w PSU and 1-bestec 250w

2x substandard PSUs do not make 1x good PSU.

 

[ChrisWaters]

Why? Because I'm cheap and have a primary PSU without the 8 pin. And a secondary just sitting around

 

[USAFRet]

Why? Because I'm cheap and have a primary PSU without the 8 pin. And a secondary just sitting around

I wouldn't use that bestec on its own, much less combined with the other unknown PSU shaped object.

I get "cheap". But are you prepared to replace ALL of your other components, when this conglomeration kills them?