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Laptop not finding 2nd monitor through KVM switch

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Blaylock

"That Backfired" Senior Member
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Jun 5, 2013
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So I finally broke down and bought a KVM switch for my Work From Home/Play From Home battle station. The model I bought is linked here. This is a display port 1.4 compatible version so that I can maintain 144hz on my 1440 monitor. I have verified the DP on the laptop works when connected directly to the monitor but when connected through the KVM the second monitor isn't detected. The Desktop and keyboard/mouse do work through the switch just fine. So the only thing that does not work is the Display Port from the laptop when connected to the KVM. Here is what I have tried to fix the problem...

Reboot the laptop
Reboot the KVM (USB powered from either source)
Rebooting in opposite order
Connecting the DP directly to the monitor (this works but my monitor only has a single DP input)
Connecting the laptop directly to the monitor with HDMI (eliminating the KVM-how I am currently running it)

The KVM is keeping me from having to switch my KB/mouse between systems after I'm done working and that's fine. But honestly, I would rather just get the DP to work on both so all I need to do is press the button and it switches over the way it is intended.

Any help is appreciated.
 
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Joined
Dec 13, 2005
Are you sure you linked to the right switch? Looks like the one linked is USB only and well...that might be your problem :D

But did you try switching between DP ports on both the laptop and desktop?

Edit: And by "switching DP ports" I mean swapping the KVM ports used for both - realized my phrasing was off.
 
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Blaylock

Blaylock

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I did link the wrong one. Good catch. (link updated) :)

Yes, I tried the laptop with input 1 and input 2 as well as the desktop with the same results. The desktop worked in either port, the laptop didn't work in either.
 
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Blaylock

Blaylock

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Did you swap DP cables?
I tried 2 different cables to confirm they worked when connected directly to the monitor and they both worked. I did not try different combinations through the switch as they are the same. If they work they should work, no?
 
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Blaylock

Blaylock

"That Backfired" Senior Member
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I had some time yesterday to get back to this. First I tried switching cables around Like E_D suggested. No luck. After doing some digging I found a suggestion from a Dell forum (it's a Dell Precision M6800 Lappy) to disable the "Switchable Graphics" in the BIOS. This didn't help either. So, my quest continues.
 
Joined
Dec 13, 2005
"Switchable graphics" - so something like Nvidia Optimus? Try updating the drivers? I know if it's disabled in bios it shouldn't be kicking on, but can't hurt.
 
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Blaylock

Blaylock

"That Backfired" Senior Member
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Yes. It has an Intel integrated graphics and an Nvidia Quadro K3100M. Updating the drivers isn't an option for me as this is all driven by IT.

For clarity, I can get the laptop to display through the Display Port. The issue is it isn't recognizing the second monitor when the KVM switch is added into the mix. Without the KVM everything is working as expected.
 
Joined
Dec 13, 2005
Got it.

Was just thinking something about the driver wasn't playing nice with the KVM - either not locking down one GPU or the other or not seeing it as a proper display output.
 
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Blaylock

Blaylock

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I'm tempted to request a Docking Station just to see if that helps, though I doubt it will.
 
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Blaylock

Blaylock

"That Backfired" Senior Member
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New KVM switch ordered. This New one is DP 1.2 compatible which is the same as the DP port on the laptop. It claims 1440 @120hz instead of 144hz but I think I'll survive the loss of 24hz to get this going...we'll see.


EDIT: I know DP 1.4 is backwards compatible with 1.2 but I'm kinda reaching for straws here. If this doesn't work I'll just resort to a USB only switch, which will still be ok I guess.
 
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Blaylock

Blaylock

"That Backfired" Senior Member
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As anticipated the new switch didn't work either. I think it may have something to do with the monitor not pushing the EDID through the switch or at least not to the laptop. Either way, I'm cutting my losses and returning everything and I'm just going to settle for a USB KM switch instead. I'll keep the lappy connected to the monitor through HDMI and the gaming desktop through Display Port 1.4 for maximum resolution and frequency. I had considered trying an HDMI switch but the HDMI port is a 1.4 port which would put a maximum of 75hz to the monitor and I had read that both sources need to match rez and freq.

Thanks everyone for the advice, even if it didn't pan out. In a year or so when my work lappy gets updated to an engineering model, it will undoubtedly have a better GPU and I can revisit this then.