4 ms·

In addition to the signal issues outlined in sibling comments, a good KVM switch presents the HID devices full-time, so instead of the computers seeing USB disc

In addition to the signal issues outlined in sibling comments, a good KVM switch presents the HID devices full-time, so instead of the computers seeing USB disconnect/reconnects, they don't see any difference at all. This requires a complete USB implementation including HID protocols and something to translate real-keyboard and real-mouse signals into the virtual USB devices. There are similar considerations regarding DDC passthrough on monitors for resolution negotiation and so forth. A bad KVM presents to the computer as though the user is disconnecting all the input devices and the monitors every time you switch. These are indeed much simpler and cheaper devices but they cause all kinds of quality-of-life issues when you use them regularly.

modeless 6y ago
Why shouldn't a computer be able to handle reconnection of peripherals without quality of life issues? It's pretty silly if this pure software issue is the reason KVM hardware has to be so complex and expensive.
- stonogo 6y ago
  Some peripherals require configuration after connection. Waiting for this can suck. I'm including monitors here -- a bad implementation will present, as an example, monitors out of order. Another problem you run into is inadvertently cycling through connections too quickly, which can show as devices being disconnected during initialization, causing some systems to flag the device as malfunctioning and refuse to initialize it next connection. Of course it's easy to say that these are silly problems that should have pure software fixes, but Microsoft and Apple don't exactly accept patches. Let's not pretend that software is optimal.
- aetch 6y ago
  You can see for yourself by disconnecting your monitor in a multi monitor setup or opening your laptop lid if you use the laptop on a dock. Computer windowing systems seem to take a moment to reposition all the windows and might not remember to redistribute your windows when the monitor count changes.
  - formerly_proven 6y ago
    For many years I was happy with my multi-monitor setups. I'd use multiple screens for work, and turn all off except the center one for watching movies or playing games (because the backlight bleeding of the other screens was annoying, even with a 100 % black image). That's not possible any more. Microsoft, VESA, nVidia say no. This mustn't be possible. (Actually it used to be possible to add a registry key in Windows 7 that disabled all of this bullshit, but Microsoft wisely decided in Windows 10 to remove that. It must not be done.) Turning compliant DisplayPort devices off while using a compliant operating system must always garble all windows and shuffle desktop icons around. The spec says so. So it must be. The will of the ancients. (nVidia will allow you to turn this off, if you are using a Quadro card - then you can use EDID emulation even on display-ports, which causes the OS to think the display is always connected - and more importantly - turned on. One of these areas where Linux is ahead -- although Linux is back to garbling windows like the rest in case you do actually decide, as an individual with agency, not a compliant operating system, to change the arrangement of displays.)
- qppo 6y ago
  To be honest it probably comes down to being a non trivial problem to get it to be perceptually seamless and a rare enough event that people don't have the incentive to fix it. Most people aren't plugging/unplugging monitors often
  - closeparen 6y ago
    Seems pretty standard in tech offices to a) have one or two external monitors on your desk, and b) disconnect/reconnect them from your Macbook every time you get up for a meeting. They still handle it horribly though. My favorite is how macOS used to assign the logical displays randomly, so I'd have to fix the arrangement in Displays preferences several times every day.
comboy 6y ago
I have one of those bad KVM switches. How do I know which one to buy to have a good one?
- formerly_proven 6y ago
  Level1 sells KVM switches that are said to be quite good for their money.
zachrose 6y ago
Definitely didn't imagine that KVM switches could actually be that good when I asked the question. (I've obviously never used one.) Thanks!
babuskov 6y ago
I have one that's in-between. The monitor is always "present", only the keyboard and mouse get (dis)connected. It works fine, since it avoids the biggest problem of adjusting the screen resolution which can reposition desktop icons, etc. The only drawback is a 3-4 delay as USB mouse/keyboard is reconnected. The price was around $50 IIRC.

modeless 6y ago

Why shouldn't a computer be able to handle reconnection of peripherals without quality of life issues? It's pretty silly if this pure software issue is the reason KVM hardware has to be so complex and expensive.

stonogo 6y ago
Some peripherals require configuration after connection. Waiting for this can suck. I'm including monitors here -- a bad implementation will present, as an example, monitors out of order. Another problem you run into is inadvertently cycling through connections too quickly, which can show as devices being disconnected during initialization, causing some systems to flag the device as malfunctioning and refuse to initialize it next connection. Of course it's easy to say that these are silly problems that should have pure software fixes, but Microsoft and Apple don't exactly accept patches. Let's not pretend that software is optimal.
aetch 6y ago
You can see for yourself by disconnecting your monitor in a multi monitor setup or opening your laptop lid if you use the laptop on a dock. Computer windowing systems seem to take a moment to reposition all the windows and might not remember to redistribute your windows when the monitor count changes.
- formerly_proven 6y ago
  For many years I was happy with my multi-monitor setups. I'd use multiple screens for work, and turn all off except the center one for watching movies or playing games (because the backlight bleeding of the other screens was annoying, even with a 100 % black image). That's not possible any more. Microsoft, VESA, nVidia say no. This mustn't be possible. (Actually it used to be possible to add a registry key in Windows 7 that disabled all of this bullshit, but Microsoft wisely decided in Windows 10 to remove that. It must not be done.) Turning compliant DisplayPort devices off while using a compliant operating system must always garble all windows and shuffle desktop icons around. The spec says so. So it must be. The will of the ancients. (nVidia will allow you to turn this off, if you are using a Quadro card - then you can use EDID emulation even on display-ports, which causes the OS to think the display is always connected - and more importantly - turned on. One of these areas where Linux is ahead -- although Linux is back to garbling windows like the rest in case you do actually decide, as an individual with agency, not a compliant operating system, to change the arrangement of displays.)
qppo 6y ago
To be honest it probably comes down to being a non trivial problem to get it to be perceptually seamless and a rare enough event that people don't have the incentive to fix it. Most people aren't plugging/unplugging monitors often
- closeparen 6y ago
  Seems pretty standard in tech offices to a) have one or two external monitors on your desk, and b) disconnect/reconnect them from your Macbook every time you get up for a meeting. They still handle it horribly though. My favorite is how macOS used to assign the logical displays randomly, so I'd have to fix the arrangement in Displays preferences several times every day.

comboy 6y ago

I have one of those bad KVM switches. How do I know which one to buy to have a good one?

formerly_proven 6y ago
Level1 sells KVM switches that are said to be quite good for their money.

zachrose 6y ago

Definitely didn't imagine that KVM switches could actually be that good when I asked the question. (I've obviously never used one.) Thanks!

babuskov 6y ago

I have one that's in-between. The monitor is always "present", only the keyboard and mouse get (dis)connected. It works fine, since it avoids the biggest problem of adjusting the screen resolution which can reposition desktop icons, etc. The only drawback is a 3-4 delay as USB mouse/keyboard is reconnected. The price was around $50 IIRC.