What would have happened if I connected an EPS cable to an 8 pin connection in a GPU?
 
Didn't actually happened to anyone I know, but I got into a discussion with a friend about this.
It doesn't have to be an EPS cable, basically just a wrong PSU cable can do this.
To make the question a bit more clear - both sense pins are connected to 12v instead of ground, some of the 12v are connected to ground, a whole mess.
 
Basically the reason I am asking is because a friend of mine ordered custom cables to his PSU and I decided to take a look before he started using them.
I went ahead and checked the pinout diagram of his PSU and they didn't match to the custom cables he received.
At this point I got curious what would have happened if he actually used those cables.
 
Will the GPU die?
Does it have some sort of protection using the sense pins?

Sajin
Should not be possible as the PCIe 8-pin connector was designed to have a completely different arrangement of pin shapes than the existing EPS12V connector. These are shown in the image below (notice the difference in bevelling on the corners):
 

 
Using the wrong cables that aren't for your psu can result in fried hardware.

It is a theoretical question, so lets just change it to using wrong PSU cables - but where both sense pins where connected to 12v.
My question is if the GPU has some sort of protection mechanism for a situation like that or not.

LucyMor
It is a theoretical question, so lets just change it to using wrong PSU cables - but where both sense pins where connected to 12v.
My question is if the GPU has some sort of protection mechanism for a situation like that or not.

Yes, the cables are pinned to where they should NOT go into the power ports without being the correct one. If someone is jamming an EPS cable into their GPU, they have already leveled up on the scaled of wrong things to do, and they are looking to do damage:



Before you say, “they look the same” note pin 4 on both cables. Ever tried to stuff a square peg into a round hole? So, theoretically, it shouldn’t be able to happen since in reality it has already been addressed.

BUT, you will find people that take cables that are NOT built by the manufacturer of their PSU, like a sata cable for example, and they will absolutely fit the data connector on the product. Let’s use a Nu Audio Card as an example, a Corsair Sata connector looks to have the same connector as a seasonic connector, but the pin out on the PSU side is completely different.. so what happens? When the user hits power, the Nu Audio Explodes. Not theoretical at all. Actual fact. There is a whole thread about it.

We had a guy install PCIe cables backwards a few weeks ago. Nothing powered up.  So the protection circuits on either the GPU or PSU did their job.  When he installed them correctly, it worked, with apparently no noticeable damage.

the_Scarlet_one

kevinc313
We had a guy install PCIe cables backwards a few weeks ago. Nothing powered up.  So the protection circuits on either the GPU or PSU did their job.  When he installed them correctly, it worked, with apparently no noticeable damage.

That was a PCI cable all around. The PSU side plugged into the GPU, and the GPU side plugged into the PSU.

That’s not a scenario of an EPS cable being plugged into a GPU, but does give some hope that the PSU would recognize an issue.

Don't underestimate the power of someone who wants an incompatible cable to install into a port where it shouldn't be plugged.  I've seen a guy plug in a 24pin cable upside down, and the system actually ran.  Voltages in the BIOS were LOL, and completely unstable, but the person managed to avoid a fire.