Strange behavior with DP to Mini DP cable

[beyonddc]

I have a Acer B286HK 28" 4K monitor, it has a DP and a mini DP input. I want both my laptop and my gaming desktop connect to this monitor.

Originally I want my laptop to connect to this 4K monitor via a DP to Mini DP cable because the monitor's manual said mini DP input supports only up to 30 Hz refresh rate and DP input supports 60 Hz refresh rate.

When I connect my laptop using the DP to Mini DP cable, the monitor would just flicker non-stop so I ended up using a regular DP cable to connect from laptop to the monitor.

I use the same DP to mini DP cable connect from my desktop to the monitor and it would work with no issue. I can get my 4K resolution but only with 30 Hz refresh rate as advertised in the monitor's manual.

My question is why the cable wouldn't work on the laptop but work on the desktop? I am confused....

 

[rtangwai]

Sounds like a bad cable to me.

I couldn't get 4K 60Hz on my BDM4350UC using DP with any of my cables - even the one that came with the monitor.

I eventually bought a certified Startech one (3m long) and it has been working flawlessly.

I'm surprised there is a difference between the DP and mini-DP ports on that monitor, as far as I know the specs are identical for DP vs mini-DP, just the connector is smaller in mini-DP.

It's possible the issue is that the mini-DP port is DisplayPort 1.1a while the DP port is DisplayPort 1.2 - you need to dig deeper into the monitor's manual to find out.

An easy way to prove it is to get a mini-DP-to-DP adapter and plug it into the cable to see if it behaves the same way on the DP port as it does on the mini-DP port of the monitor.

 

[beyonddc]

Sounds like a bad cable to me.

I couldn't get 4K 60Hz on my BDM4350UC using DP with any of my cables - even the one that came with the monitor.

I eventually bought a certified Startech one (3m long) and it has been working flawlessly.

I'm surprised there is a difference between the DP and mini-DP ports on that monitor, as far as I know the specs are identical for DP vs mini-DP, just the connector is smaller in mini-DP.

It's possible the issue is that the mini-DP port is DisplayPort 1.1a while the DP port is DisplayPort 1.2 - you need to dig deeper into the monitor's manual to find out.

An easy way to prove it is to get a mini-DP-to-DP adapter and plug it into the cable to see if it behaves the same way on the DP port as it does on the mini-DP port of the monitor.

I might just buy another cable to test it out.

But it seems like there's a confusion.

I use the same DP to mini DP cable on my desktop and laptop. It works when I use that cable on desktop and doesn't work on laptop. That's what bothering me.

 

[rtangwai]

Ah, okay - since it is a laptop I'm wondering if they cut corners on the DP spec of the port which is causing your issues with that cable (especially if the cable isn't certified).

30Hz isn't that demanding on bandwidth so I'm a bit surprised it is a problem - unless maybe your laptop is attempting to send a 60hz signal? What happens when you change the resolution to 1080p or 1600p, does it still flicker?