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I just bought a new Dell P2415Q monitor and am having trouble getting it connected to my old Windows 8.1 PC with an nVidia GeoForce 710 video card.

It will connect OK to the monitor over a DVI->HDMI cable @ 3840x2160 @ 30Hz. 30Hz is fine with me-- no gaming or video playing on this PC.

But I want to connect it using a mini-DisplayPort connection (not HDMI) because I want to run the video signal through a StarTech 4K KVM Switch which only has mini-DP inputs. That's where I'm getting stuck.

What's the right cable and/or adapter to connect my video card (which has DVI and HDMI outputs) to a mini-DP connection?

I tried a Benfei 4K Mini DisplayPort to HDMI cable which didn't work. Not only did the monitor not detect a signal when running through the KVM switch, it also didn't work when I directly connected my PC to the monitor. This cable also didn't work when I tried connecting via the HDMI output of my MacBook Pro, so I suspect that the problem is the cable (or the cable+monitor combination) not my video card. FWIW, my MacBook Pro works fine mini-DP-to-mini-DP cable to this monitor, either directly connected or through the KVM switch.

So, should I:

  • try a different brand of HDMI-to-Mini-DP cable, and if so what should I look for?
  • try a DVI-to-mini-DP cable instead?
  • get an active adapter between HDMI or DVI to mini-DP?

Finally, do cables and adapters have "sides", meaning that a Mini-DP to HDMI cable is different from an HDMI to Mini-DP cable?

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After learning more than I ever wanted to about video cables and standards, here's what's going on.

First off, video adapters and cables are not always bidirectional. An inexpensive "HDMI-to-Mini-DisplayPort" cable is designed to convert from a Mini-DP output to an HDMI input.

But if you want to go the other way, from an HDMI output (like an older video card) to a DisplayPort input (like a monitor or KVM switch) then you need a much-more-expensive "converter" like one of these.

The same goes for other kinds of conversions. Some conversions can be accomplished with simple "passive" (no computer chips) cables or adapters while other conversions require "active" converters that run the signals through electronics. And apparently those active conversion electronics are more complicated and therefore expensive in both money and electrical power.

Here's my understanding of the rules:

  • HDMI and DVI conversions can be passive in both directions.
  • DisplayPort outputs can send an HDMI or DVI signal thanks to Dual Mode support. This enables passive cables and adapters from DisplayPort to HDMI or DVI.
  • DisplayPort and Mini-DisplayPort are pin-compatible so cables can be passive when converting from mini to non-mini DP.
  • I don't know about VGA

UPDATE:

I ordered an HDMI to DisplayPort converter, and it worked OK but had quite a few problems: slow refresh rate, laggy cursor, didn't work well with my KVM switch when rebooting, etc. So I bought a new DisplayPort video card for $70 and all problems went away: KVM shows video at reboot, cursor looks normal, I'm getting 60Hz refresh rate @ 4K, and to top it off the new card uses 5 less watts ($1 per month less electricity!). So if I had to do it over again I wouldn't have bothered with converters-- instead I'd have just bought a new low-end video card.

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