DP++ vs DP - will only one work?

[Niklas Ternvall]

I've made a 3 monitor gaming-pc.
It works great!

I borrowed a DP-cable of work, while waiting for the one I ordered. It didn't work so the store send yet another non-functioning cable.
They all have the same spec - same product- and serial-name!

I noticed that the one that works has the DP++ logo while the others don't.
No stores I've visited tells if it's DP or DP++, so it cant be important right?

I don't want to return another cable if I'm at fault.

____________________________

If spec. is of interest:
3 screens: HP 2310ei
graphics: ASUS - Radeon R9 270X
Cables: 2x DVI-d & 1xDP++/DP

 

[Suztera]

DP++ is Dual-mode DisplayPort. It means you can use passive adapters DP to DVI/HDMI cables. It's still a Displayport.