Need help getting KVM to work with R9 390 and LG ultrawide 2560x1080

jkelley9

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I could really use your help. I can't get video through a new KVM switch I just bought. It looks like the KVM is working fine (I tested all ports with my laptop) but it's not working for my PC.

For my PC I have an MSI R9 390. 2 Dual-link DVI-D, max res 2560 x 1600 @60 Hz, 1 HDMI (1.4a) max res 4096×2160 @24 Hz (1.4a), and 1 DisplayPort (1.2) max res 4096×2160 @60 Hz.

The monitor is an LG 34UM57 that I'm trying to run at 2560x1080 ultrawide (not even 4k!) with freesync. The monitor has displayport and HDMI inputs only.

I typically connect the PC to the monitor with an HDMI cable and an active displayport-to-HDMI adapter (from the displayport connector on the card). This works fine.

The KVM I ordered is this one: https://www.amazon.com/gp/product/B00ZR18VPS/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1
(the 2 port, miniDP version)

I ordered some cables from monoprice. The one I ordered for the PC was "Select Series Mini DisplayPort 1.2a to HDTV 4K Capable Cable." I hooked the HDMI end to my displayport active adapter (displayport-to-HDMI). That didn't work. I also tried going to the HDMI port on the R9 and used the same cable I ordered in reverse, HDMI to miniDP on the KVM, then used my existing miniDP to displayport to go to the monitor.

I'm not getting any video, at all. My laptop has a miniDP connection and I just used the cables that came with the switch and it worked just fine.

Any advice?

Thanks so much!
 

panathas

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Usually KVM switches don't like adapters (active or passive). So in your case you should use only displayport cables without using HDMI adapters between the GPU and the KVM switch. You should only try to connect the KVM to your GPU with a pure displayport cable and then use a similar cable from the KVM to the monitor. Now if you need to use the monitor's HDMI input, you could try to use a displayport to HDMI adapter from the KVM to the monitor (as a test) but keep in mind that it may not work.
 

jkelley9

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I did try that way. I had a 1.2 displayport-to-miniDP cable that I went from the R9 390 to the KVM, and then I used the new cable I had bought (HDMI-to-miniDP) to go from the switch to the monitor. I did this without any active adapters.

Still no video in this config :(

 

panathas

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A HDMI-to-miniDP cable is in reality an adapter cable because it changes the connection type. Only HDMI to HDMI and displayport to displayport cables don't use adapters. Also if you check the ratings on that KVM switch you'll see that a lot of other users are having issues with it. So since you have a KVM switch, you should only try to use mini-displayport to displayport cables. If that doesn't work you are probably facing a compatibility issue as many other owners of that specific KVM switch.
 

jkelley9

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Wow I had no idea. So miniDP to DP is still the same display type then?

I ordered another miniDP to DP cable and will let you know if it works when it arrives Monday (fingers crossed!). Otherwise the switch is going back lol.
 

panathas

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Yes miniDP to DP is a pure displayport type cable so logically it should work in your case unless you are also facing a strange compatibility issue with your whole setup (GPU, monitor). Good luck.
 

jkelley9

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Thank you for your help. The new cables solved the problem!
 

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