IOGEAR4-Port DisplayPort KVMP Switch - 4K 30Hz - 2-Port USB 3.1 Hub Rate 5Gbps - Keyboard Mouse Input - 7.1 HD Audio - Front Panel Selector - TAA Compliant - Mac/Win - GCS1904 Black

So, yes I can hook up 4 devices to this KVM and use my 4K monitor over DP. However I hit the following issues, which to me renders the KVM pretty much useless:- Display emulation isn't available, which means the monitor will be redetected AFTER EVERY SWITCH, taking about 10 seconds each round. This also leads to losing the screen layout on computers which use the KVM monitor as a second display (say Windows' "Extend to Desktop" mode).- The max supported 4K resolution isn't stable using the supplied cables, or higher quality ones I tried. Screen flickers once in a while (esp after complex scenes), and display goes dark for 5-10 seconds. This doesn't happen when I connect the source machine directly to the monitor using the same cables, which means it's not a problem caused by the cables, the computer or the monitor. THis proves the KVM has signal quality issues. Bottom line is I'm forced to downgrade to 2560x1440 resolution. Unacceptable after having paid $270 while product specs clearly boast this feature.- The KVM wasn't able to detect my Microsoft Wireless Ergo Keyboard when connected to the KB port at the back. I had to connect the receiver to the front port, which in turn means the keyboard is also redetected (beep-boop!) every time I switch to a different computer. Super annoying after I paid $270, this is a very common KB and it's supposed to work per product specs.Bottomline is this KVM isn't good for switching back and forth. It's only usable if your workflow involves having a single active computer hours on end, and not need to switch every 15-20 minutes like I need to.

IOGEAR GCS1904 4-Port 4K UHD DisplayPort KVMP Switch with USB 3.0 Hub (TAA Compliant)I agonized over the decision of which KVM to buy... so many choices, but most were very poorly reviewed. Everybody complaining about losing handshakes (HDCP is defective by design) and nothing working right. I have an eGPU serving as a TB3 docking station for my Thinkpad, and a standard Dell docking station for my Dell... I regularly have occasion to work on other PC's and even a docking station for my Samsung cell phone (it was free). I *HATE* plugging and unplugging cables and wish everything had its place and was in said place...I've had *ZERO* trouble with this station - even with the complex eGPU setup.

I should have paid attention to "no video after replacement." I, too, have liked IOGear for quite some time, but when I tried to get this item to work, it would not provide any video output. I checked all cables and inputs. The cables all worked flawlessly when connected directly to the computer and monitor, but no video output from the KVM. It also did not like running both my Razer Naga mouse and my RealForce RGB keyboard plugged into the "appropriate" ports on the back, but I'm not surprised; I have yet to find a KVM that will support these natively. All I can say is, I'm not even bothering trying to go through customer support on this, I am so thoroughly disappointed. Chalking it up to a lesson learned, and looking for something else. "Buyer beware" has never been so acutely felt as this.

This item simply did not work for me: I could not get any video. I spoke with tech support, who advised returning the unit for a replacement, but the replacement also failed. My monitor is an HP ZR2740w, not an inexpensive device nor an off-brand, and it supports displayport wonderfully, with a native resolution (2560x1440) well with the advertised range of this switch.This is hugely disappointing, as I have been a fan of iogear kvms since 2009, when I purchased a miniview vga switch (GCS634U). I upgraded to a dual-link dvi switch (GCS1204G) in 2012. Both of these switches worked flawlessly for years - the latter still does (I use it with displayport to dual-link dvi adapters for some devices). The current unit was intended as a further upgrade. It would have been, if it worked, but a KVM without V is not much use.

We had to try three IO Gear KVM switched to finally find this one able to handle switching between PCs with Displayport connectors and other PCs with VGA connectors. We finally did and it works...Advice to IO Gear compatibility needs to be specified more clearly.

I bought this because the description said multi-platform support for Windows, Linux, and Mac. That's just not true, and as such I needed to return it, although I did try to make it work. Spoiler: it didn't work.The IOGear Tech Support (despite being rude) also informed me that if you use an adapter, it is not supported. There are exactly ZERO Mac computers with DisplayPort, so you MUST use an adapter. Hence, to say it is multi-platform just is not true. If you want to connect a Mac, look elsewhere. If you want a company that treats you well, also look elsewhere.

This particular model can only work if the computer OUTPUTS 30HZ. This has not been a mode on modern gpu in more than half a decade. on top of that the implementation of displayport is not tolerant to adapting to HDMI in or out so most PCs plain can't work with it. I ended up upgrading to the GCS1934m which is marginally better.

The switch doesn't manage the display IDs between the two systems, so if you are using two computers with different resolutions, then you will find that the computers may resize their windows every time you switch between them. I don't have this issue, as my both of my computers use the same resolution, but I expect that this would be a deal-breaker for others.

Pros:- works with both Mac and PC- much smaller than I expected as I previously used the GCS1644 with dual DVI- includes 4 sets of DP and USB3 cables- power adapter is a brick vs a wall wart- works with Caldigit TS3 Plus TB3 dock for mac computers- made with metal chassis- displays nicely on a UHD tvCons:- doesn't work with adapters (HDMI, DVI, Thunderbolt 2 to DP)- up to 5 second delay when switchingI bought the GCS1904 4-Port DisplayPort KVM to connect these computers:- Lenovo M83 Tiny- 2016 MacBook Pro- Zotac BI320- 2014 Mac MiniIt works well with my M83 and MBP but not the BI320 and MacMini. I use a TS3 Plus dock with my MBP. I don't use the BI320 and macmini as much any more so although it's not working for all my computers, it works for the 2 main computers that I use probably 99% of the time. I can still use this KVM to switch the keyboard and mouse for my BI320 and macmini for now until I am able to find a display solution for them (possibly an adapter with an active monitor converter). The BI320 can only do 1920 x 1080 but that shouldn't matter.I originally bought a much cheaper priced Tesmart HDMI KVM switch but returned it because it did not work well with all of my mac computers (4 in total including my wife's 2013 MBP and another 2014 macmini). The display kept flashing every 10 seconds.*Update - May 20, 2020*I bought the Cable Matters HDMI to DisplayPort Adapter (includes an active monitor converter) and now my BI320 and macmini both work with the GCS1904. So I changed my 4 star rating to 5 star since I needed the right adapter for these to work properly. So the only con is the delay when switching but it's not that big of a deal since I don't constantly switch between computers.

You need HDMI /DVI to DP converter if your pc / video card doesn't have display port output. The cheap adapter you see is for display port video cad to DVI/HDMI monitor and only work on this kvm switch if you use it between kvm output to your dvi/hdmi monitor. (It also need to active adapter.)

As expected !