Dual (DVI) monitors and KVM switches

HankB · Sep 9, 2014

Hi all,
I'm not sure if this is the correct forum, but I am using a GTX 460 video card and part of the question involves that.

I'd like to connect my monitors to another PC using a KVM switch. One PC uses a GTX 460 card which has two DVI connectors. As near as I can tell, the ports are Dual link DVI and I think that means that each port can connect to two monitors using a DVI splitter cable. (The connectors look like the ones at http://en.wikipedia.org/wiki/Digital_Visual_Interface and labeled "DVI-D (Dual Link.)

The other PC lists the video card (under Win8.1) as "ATI Radeon R7 200 Series. It has a similar DVI connector and a Display Port port as well.

My current (pre-KVM) setup is using two DVI cables to connect two 1600x1200 LCD monitors to the two ports on the GTX 460. However, I am not seeing a lot of DVI capable KVM switches with a pair of DVI ports. This leaves me wondering if I can connect one port on the GTX-460 and one port on the Radeon R7 200 Series to the two inputs on the KVM switch and then connect a DVI splitter to the outputs of the KVM switch to drive the two monitors. Is this the kind of thig that Should Work(tm) or do I have to look for a KVM that supports Dual Link DVI (or do I need to look for a KVM switch intended for doal monitors on DVI connectors?)

I wonder if I can use something like this: http://www.newegg.com/Product/Product.aspx?Item=N82E16817399139 for $65 US or if I have to spring for something like http://www.newegg.com/Product/Product.aspx?Item=N82E16817707257 for about $90 US. Or go with something like this: http://www.newegg.com/Product/Product.aspx?Item=N82E16817402035 which seems guaranteed to do the job.

Thanks!

ninjacore · Sep 10, 2014

Unfortunately, I think the second option you linked (pricier one) will be the only way to do hardware switching with multiple displays.

Have you considered using Windows Remote Desktop to connect to the secondary PC from the primary? As long as they're both on the same LAN (maybe just plug them into a cheap, high speed switch?), there shouldn't be a much input lag as there is with WAN Remote Desktop connections. I would give it a try first, since you likely have everything you need for it. Could save you money in the end if you're happy with it. (I've not tried this out, by the way, so it very well could turn out to not be an option. I might give it a go tonight after work tho

)

TransformedBG · Sep 10, 2014

You could just remote into the other pc if you didnt want to use a switch.

HankB · Sep 10, 2014

ninjacore said:
Unfortunately, I think the second option you linked (pricier one) will be your option for hardware switching of inputs.

Have you considered using Windows Remote Desktop to connect to the secondary PC from the primary? As long as they're both on the same LAN (maybe just plug them into a cheap, high speed switch?), there shouldn't be a much input lag as there is with WAN Remote Desktop connections. I would give it a try first, since you likely have everything you need for it. Could save you money in the end if you're happy with it. (I've not tried this out, by the way, so it very well could turn out to not be an option. I might give it a go tonight after work tho )

I got permission to order the more expensive one.

The suggestion to remote in has a lot of merit but some potential challenges. First of all, I don't know if there is any remote S/W that will handle a dual monitor setup. I suppose I could try to run a session on each monitor but I think that the one I used in the past (logmein) would only support one session on the remote. Another issue is that my PC runs Linux whereas the remote runs Win8.1. And the actual work is done on a VMWare guest that is running Win7.1. VMs can introduce interesting keyboard effects when the VM grabs the keyboard and managing that remotely could be a problem.

An additional wrinkle is that the Windows PC is connected to my LAN through a Cisco box that routes it through a VPN to another site so it is not directly accessible on my home LAN. I'm not sure that matters to the remote S/W since it may to through a remote server anyway, but it does mean that the machine sitting at my feed is accessible through a firewall about 50 miles from me.

That's a good suggestion and I'm sure there are many situations where remote access is a better solution than a KVM, but I'm not sure this is one of them. I could easily see it being more than $200 worth of headache.

ninjacore · Sep 10, 2014

Couldn't agree with you more. With the complexity of your situation, the hardware solution will likely save you a lot of time. :thup:

HankB · Sep 13, 2014

I'm reminded of the line from Kill Bill "You didn't think it was gonna be that easy, did you?" :eh?:

In other words, I HATE KVM switches.

And I'm learning the difference between DVI-I and DVI-D. It turns out the KVM switch came with DVD-I cables and my monitors are DVD-D. That wouldn't be an issue except the Displayport to DVI adapter for the work PC is DVD-D. I can connect both of my monitors through the KVM switch but can only connect one monitor from the work PC until I get an adapter. The monitor on my PC which is connected to that port on the KVM flashes on and off. I'm hoping that is just an artifact of having the alternate port disconnected. Otherwise this KVM is going back.

It also has difficulty with my keyboard. I have an old clicky Northgate keyboard. Too many times it doesn't come up when I start things. I have to plug and unplug the USB adapter to get it working. I have an IBM Model M that I could try. Both keyboards are the old PS/2 style plug in and I have a USB adapter. It works 100% of the time plugged directly into the PC.

The mice work flawlessly.

I have not bothered with the audio cables.

Automata · Sep 13, 2014

For what it is worth, TeamViewer lets you pop out each monitor into a new window or tab. I know you have a switch now, but someone may read this thread and be looking for remote access.

ninjacore · Sep 13, 2014

Ugh, yea they can definitely be a pain. I remember it taking me a while to get mine all configured when I used it. Other issues I ran into were input lag (infrequent, but still annoying) and a lack of nkey rollover (this might be tied into your PS/2 KB problem).

Hope you get it sorted out soon. It's terrible when you have to be so unproductive to help make yourself more productive

HankB · Sep 13, 2014

thideras said:
For what it is worth, TeamViewer lets you pop out each monitor into a new window or tab. I know you have a switch now, but someone may read this thread and be looking for remote access.

I'm mixing Linux and Windows so I don't think it would work for me. I'm sure it would be good in a Win/Mac environment. Do you know if it supports dual monitors?

I have used LogMeIn in a mixed Linux/Win environment (about 5 yeas ago) and it worked fine, but we were using single monitors at the time. It also displayed what was visible on the remote monitor. I wonder if these solutions work when the remote is running headless.

ninjacore · Sep 13, 2014

Yea, that's what he was saying, that with teamviewer you can display multiple monitors. I knew you could "see" what was on the other monitors with that app, but I didn't actually know you could pop it out into a new tab or window :thup:

I think TeamViewer might be a bit laggy for your purposes, though, even if it did work on all your platforms.

Automata · Sep 14, 2014

HankB said:
I'm mixing Linux and Windows so I don't think it would work for me. I'm sure it would be good in a Win/Mac environment. Do you know if it supports dual monitors?

I have used LogMeIn in a mixed Linux/Win environment (about 5 yeas ago) and it worked fine, but we were using single monitors at the time. It also displayed what was visible on the remote monitor. I wonder if these solutions work when the remote is running headless.

I'm using all Windows now for my important stuff, so I'm not sure how linux handles it. I know for sure you can display multiple monitors. My main desktop is 4 screens and it has no problem showing me any of them or popping out a window for each.

I believe it also routes over the LAN if it detects you are both on the same network. Remote sessions run fast for me if I'm near the system.

HankB · Oct 13, 2014

I'm still not overly fond of KVMs. The Linkskey model sort of settled down and stopped doing the monitor flash on/off thing. Maybe it just needed to burn in. However it still did not work well with my old clicky keyboards. And the right monitor did not have a clean display. There were artifacts. I finally bit the bullet and ordered a Das Keyboard which comes with mechanical switches and purports to be KVM compatible. It did and it was. While not as clicky as my IBM Model M, it has a decent feel and key travel. I had already decided to have a go with another KVM switch. This time I tried a Black Box unit because I thought that Black Box was a more reputable manufacturer. It actually performed more poorly than the Linkskey unit. And it did not include any cables so I had to purchase cables for it. :>( Gah! Unfortunately some time during the process of trying to get it working, I believe I dislodged the video card in my tower. It was pretty solidly mounted but logging in remotely I could no longer see it listed as a PCI device. I opened the case, removed and reinstalled the card and it reappeared as a PCI device.

I decided to go low end. I checked out reviews of various KVM switches and while none of the seemed to be universally liked, the IOGear units seemed to get the best reviews overall from purchasers. I bought this one to see what it would do. I've tried it with one wireless mouse and Das Keyboard and it switches them just fine. One wrinkle is that Das Keyboard requires two USB connections (one marked 'keyboard' and the other 'hub') and this KVM only has two USB ports. I plugged the 'hub' cable into the back of one of the PCs as I felt it was only there to provide additional power. I tried it with both video ports on the Dell (DVI and DisplayPort) and it seemed happy with that. One funny thing was trying to boot my Linux box with the monitor connected to the DisplayPort output on the Dell. Switched to my tower and hit the power switch and the monitor never came on. Ifter a few seconds my tower shut down and restarted. It looked like it was dealing with a failed POST by restarting. before it took my BIOS settings back to default I interrupted it. I shut down the Dell box and found that my tower booted normally after that.

Other than the possible temporary monitor anomaly, this latest KVM seemed to perform admirably. At the moment I have it set up to switch keyboard and one of my mice and the other monitor is connected to my Work PC. For now that will do. With the work schedule as it is, I don't have time for my personal development projects for the most part. And I can switch between PCs at the push of a button.

I'm wondering what I should do next. IOGEAR makes a dual monitor KVM for $320. Or for another $78 I can get a second single monitor KVM that will work. And it will get me 4 USB ports. Their dual monitor switch only provides a total of three USB ports. I lose the ability to switch both using keyboard or mouse shortcuts and I would need to push two buttons to switch, but for a working setup I think I could sacrifice that. Cabling is a little messier too, but I think I can deal with that.

Is there anything I'm overlooking by considering two KVM switches vs. a single dual monitor KVM switch? At half the cost dual KVMs seem like a good solution.

Rexpro · Oct 27, 2015

suggestion setup of dual-monitor/ dual-header KVM switch over link two single

HankB said:
I'm still not overly fond of KVMs. The Linkskey model sort of settled down and stopped doing the monitor flash on/off thing. Maybe it just needed to burn in. However it still did not work well with my old clicky keyboards. And the right monitor did not have a clean display. There were artifacts. I finally bit the bullet and ordered a Das Keyboard which comes with mechanical switches and purports to be KVM compatible. It did and it was. While not as clicky as my IBM Model M, it has a decent feel and key travel. I had already decided to have a go with another KVM switch. This time I tried a Black Box unit because I thought that Black Box was a more reputable manufacturer. It actually performed more poorly than the Linkskey unit. And it did not include any cables so I had to purchase cables for it. :>( Gah! Unfortunately some time during the process of trying to get it working, I believe I dislodged the video card in my tower. It was pretty solidly mounted but logging in remotely I could no longer see it listed as a PCI device. I opened the case, removed and reinstalled the card and it reappeared as a PCI device.

I decided to go low end. I checked out reviews of various KVM switches and while none of the seemed to be universally liked, the IOGear units seemed to get the best reviews overall from purchasers. I bought this one to see what it would do. I've tried it with one wireless mouse and Das Keyboard and it switches them just fine. One wrinkle is that Das Keyboard requires two USB connections (one marked 'keyboard' and the other 'hub') and this KVM only has two USB ports. I plugged the 'hub' cable into the back of one of the PCs as I felt it was only there to provide additional power. I tried it with both video ports on the Dell (DVI and DisplayPort) and it seemed happy with that. One funny thing was trying to boot my Linux box with the monitor connected to the DisplayPort output on the Dell. Switched to my tower and hit the power switch and the monitor never came on. Ifter a few seconds my tower shut down and restarted. It looked like it was dealing with a failed POST by restarting. before it took my BIOS settings back to default I interrupted it. I shut down the Dell box and found that my tower booted normally after that.

Other than the possible temporary monitor anomaly, this latest KVM seemed to perform admirably. At the moment I have it set up to switch keyboard and one of my mice and the other monitor is connected to my Work PC. For now that will do. With the work schedule as it is, I don't have time for my personal development projects for the most part. And I can switch between PCs at the push of a button.

I'm wondering what I should do next. IOGEAR makes a dual monitor KVM for $320. Or for another $78 I can get a second single monitor KVM that will work. And it will get me 4 USB ports. Their dual monitor switch only provides a total of three USB ports. I lose the ability to switch both using keyboard or mouse shortcuts and I would need to push two buttons to switch, but for a working setup I think I could sacrifice that. Cabling is a little messier too, but I think I can deal with that.

Is there anything I'm overlooking by considering two KVM switches vs. a single dual monitor KVM switch? At half the cost dual KVMs seem like a good solution.

If have a budget to upgrading your single-monitor kvm switch setup, I suggest looking for dual-monitor KVM switches with DDM technology (Dynamic Devices Mapping) class of KVM switch. Please google "DDM class KVM switch" and you will find the comparison table showing the advantages of the DDM class switch - no latency switching, better in HID device sharing and most importantly you still can use hot-key to quickly switch between/among connected systems. Those technologies had been around for years. It had been proofed that it should work smoothly with most of dual-head solution. However, I suggest that you call the technical support first if you have Displayport monitor with your setup.

HankB · Oct 27, 2015

Thanks for the suggestion. I may look into it.

I've been using the Linkskey for over a year now. It has its faults. Sometimes it switches USB w/out video or vice versa. But it fixes itself if I switch back and forth. I also get noise on one of the monitors from time to time but mostly if the image is black. My IDE is mostly white so the noise is not so much of an issue.

It's never been bad enough to keep me from getting work done.

Dual (DVI) monitors and KVM switches

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