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I'm running 3 servers and not sure who makes good quality KVM switches. A recommendation for a cheap 4 port KVM switch to improve my keyboard handling, would really help.

I have an old home-use KVM already but it works by disconnecting/reconnecting the USB hub as it switches, so the servers are constantly redetecting and reconnecting the KVM's hub and keyboard (causing console spam and slowness!) and keyboard connectivity is very poorly handled.

I've looked up full DDM switches but they start around £250 which I can't justify. Is there anything in between? I've tried to understand the classes of KVM switch but it's still confusing which kind I'm actually after.

In terms of connection, the devices are pretty simple: standard wired USB keyboard, standard wired USB mouse, and a monitor at the moment 1280 x 1024 but ideally up to 1920x1200 "just in case" I upgrade it. But the keyboard handling is the priority as I don't have anything that handles KB switching nicely. (I can handle VGA/DSUB monitor connectivity and if it doesn't cost too much more I'd like to know of a digital alternative - DVI or displayport.) The KVM box format is less important but smaller is better.

I'd ideally like to handle rebooting multiple machines together so I don't have to wait 3 minutes to reboot one then the next, but if getting video magic/DDC/EDID emulation (or whatevers needed for better monitor handling) in the same KVM as decent KB handling will add a lot to the cost, then it's not essential, I'll take a cheaper KVM that handles the keyboard nicely.

(Basically, as long as it handles simple video correctly - I won't be using multiple monitors or swapping monitors in use, although I might need to briefly disconnect/reconnect the monitor I'm using now and then. Even a little latency isn't a problem. The crucial factor is that good keyboard handling when switching between servers is important.)

Other than that, it's mostly about price. I'm happy buying secondhand if I knew what to look for, but I suspect this is one of those product types where you only find how well it works if you know who makes them well, or after you buy.....

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I'd ideally like to handle rebooting multiple machines together so I don't have to wait 3 minutes to reboot one then the next, but if video magic or DDC/EDID emulation (or whatever's needed to do that) will add a lot to the cost, then it's not essential.

To achieve this, you should look into KVMs made by ATEN that have the Video DynaSync feature. Video DynaSync was invented by ATEN, and they describe it in a white paper:

When the various computers wired to the KVM switch are booted up, they may or may not be able to detect the monitor’s EDID; it depends on whether the switch has connected a given computer to the user’s monitor, and whether the DDC conveys the monitor EDID to the computer. [...] Some KVM switches offer a default EDID to the computers, but this default is just an arbitrary monitor resolution. While an arbitrary EDID may allow switched computers to boot up as though they had read the actual monitor EDID, the chances are that they’ll boot with a less-than-optimum resolution. [...] In some cases the modern monitor may be unable to display anything when the user actually switches to them using an incorrect default EDID value, or the computer may take a while to re-sync to the correct monitor resolution.

ATEN solves the switched EDID dilemma by adding specially configured EDID memory to its Video DynaSync™-equipped KVM switches. When such a KVM switch is connected to an EDID-enabled monitor and turned on, the switch reads the monitor’s EDID and stores it in non-volatile memory. This memory is made available at once to all the computers connected to the Video DynaSync™ equipped KVM, and these computers are able to use DDC sensing to instantly read out the KVM switch’s stored monitor EDID. [...] In the event the monitor is not turned or connected at the time the Video DynaSync™ KVM switch is turned on, the switch directly connects the selected computer to the monitor’s EDID so it is still able to get the needed EDID data. ATEN also provides a non-volatile memory to save the EDID that it detected the last time it was used so that, when powered up the next time, the chances are the KVM switch will already have the correct monitor EDID – even if the monitor isn’t yet powered up. Since a suitable EDID is always present for the computers, there is no “seeking” time lost when switching among multiple computers, no blank screen, and no need to reboot computers just to get them to detect the optimum video value. It’s as though the computers each had a direct, full-time DDC connection to the user’s monitor EDID information.

You can also find some IOGEAR KVMs that have the Video Dynasync feature, since ATEN owns IOGEAR.

Here are a couple KVMs that match your requirements, and can be had for under $100 (which is a lot less than £250):

ATEN CS84U

  • 4-Port PS/2-USB VGA KVM Switch
  • Superior video quality - 2048 x 1536; DDC2B
  • Video DynaSync™ - Exclusive ATEN technology eliminates bootup display problems and optimizes resolution when switching between ports
  • Console mouse port emulation/bypass feature supports most mouse drivers and multifunction mice
  • Complete keyboard emulation for error-free booting

IOGEAR GCS1724

  • 4-Port VGA KVM
  • Video resolution: 2048x1536; DDC2B
  • USB or PS/2 mouse and keyboard peripherals
  • Video DynaSync™ optimizes display resolution and eliminates boot-up display problems
  • Console mouse port emulation/bypass feature supports most mouse drivers and multifunction mice
  • Complete keyboard emulation for error-free booting
| improve this answer | |
  • Their DynaSync is about monitor handling. My question is more about keyboard connectivity handling. But this is good info. I've edited the question to clarify the focus. Any hints on the equivalent for keyboard handling? – Stilez Nov 3 '17 at 9:38

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