Problem with displayport

[Misterpnk]

I have build a new pc with a asus prime z370 p2. 2070 gtx and i5 9600k and I have bought a new monitor resently that is a Dell s2719dgf every time I try to plug the dp cable it works fine but when I turn of the pc it won't power on unless I plug out the dp. The hdmi 2 works fine. ALSO I believe that for some reason while the pc is power off the dp draws power from the monitor to the motherboard I have bought two new and expensive dp cables and nothing works. I need help guys any ideas 

[nekogod]

I had a similar issue, tried several different DP cables, RMA'd the motherboard in the end and it worked fine from then on

[Misterpnk]

I want to avoid that that's why I am asking thanks

[Glenwing]

Are you using a VESA certified cable?

 

There have been issues with non-certified cables that were improperly manufactured which can cause power-related issues.

 

https://www.displayport.org/cables/how-to-choose-a-displayport-cable-and-not-get-a-bad-one/

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Recently VESA has experienced quite a few complaints regarding troublesome DisplayPort operation that ended up being caused by improperly made DisplayPort cables.  These “bad” DisplayPort cables are generally limited to non-DisplayPort certified cables, or off-brand cables.  To further investigate this trend in the DisplayPort cable market, VESA purchased a number of non-certified, off-brand cables and found that an alarmingly high number of these were configured improperly and would likely not support all system configurations.  None of these cables would have passed the DisplayPort certification test, moreover some of these cables could potentially damage a PC, laptop, or monitor.  We have not seen problems with the cables supplied by major computer brands, or major computer accessory brands, nor have we seen any problems with any of the cables that have been DisplayPort certified.

http://monitorinsider.com/displayport/dp_pin20_controversy.html

Quote

The problem with this arrangment is that one should never ever connect the DP_PWR of the source to the DP_PWR of the sink: it's impossible for both pins to have exactly the same voltage, so connecting them together would effectively result in a short circuit condition.

 

In addition, if, your GPU is powered off, while your monitor is powered on, you get a problem that's commonly called 'backdrive': a sneaker path that feeds electrical compoonents in the GPU even though nothing is supposed to have power. This can result in your GPU behaving erratically when trying to power up. In some cases, it can even damage the GPU.

 

This is why regular DP cables should never have a wire between pin 20 of boths sides of the cable.

 

Yet some DP cable manufacturers never bothered to really understand the specification and flooded the market with some cheap cables that do exactly that. This was especially common for miniDP (mDP) to DP cables.

 

If you happen to have such a cable, your best advice is to throw it away and buy a new one that doesn't have this issue