KVM switch for two PC's with thunderbolt - neither is Apple

[Polar Bear]

I have an Intel nuc and mllePB's work Microsoft laptop which I would like to share screen, keyboard and mouse with.  Currently I have to unplug the dock from one and plug it into the other.  Longer term a simple switch would be preferable.

The monitor is using an hdmi cable and the keyboard and mouse are using a single Logitech Bluetooth dongle.

Looking at KVM switches I'm not sure that I can see something which will do what I need so I was wondering if anybody out there might have a clue please?

[PaulF]

Which version of Thunderbolt?

[Polar Bear]

Hmmm.  I have no idea. 

Goes off to Google ...

[PaulF]

Hmmm.  I have no idea. 

Goes off to Google ...

Let me save you the effort USB-C or Displayport type connectors?

[Polar Bear]

USB-c.  They both appear to be thunderbolt 4 according to the spec sheets online.

[PaulF]

"USB-C KWM" in your favourite search engine will give plenty of examples.

I've got a version of this https://itpartsmaster.co.uk/products/60263323?variant=49268550959430&currency=GBP&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&infinity=ict2~net~gaw~cmp~IT%20Partsmaster%20%7C%20Desktop%20%7C%20£100%20-%20£250%20%7C%20Low%20%7C%20Shopping%20%2724~ag~~ar~694673105992~kw~~mt~&gad_source=1&gclid=EAIaIQobChMIr6Wjt8SjhQMVJoFQBh0eOQSFEAQYBCABEgJAj_D_BwE

[drossall]

I've got my personal, elderly HP Windows PC (over ten years elderly, I'd think), and a work Dell 7420 laptop (my second - two successive employers happened to issue me the same model). I use this PWay switch (at least, it looks like that one).

I got work to issue me with a Dell docking station. That's connected to the switch, so all I do is to throw the switch and plug in the docking station - I have to unplug it and plug it in to kick the laptop into life, since the laptop has no external power switch and it sits in a small gap with its lid permanently closed (while at home). I always power laptops down fully at the end of the day, which I know not everyone does.

Works really well. Very occasionally the laptop fails to start up, and I have to open its lid and press its power button.

[PaulF]

I've got my personal, elderly HP Windows PC (over ten years elderly, I'd think), and a work Dell 7420 laptop (my second - two successive employers happened to issue me the same model). I use this PWay switch (at least, it looks like that one).

I got work to issue me with a Dell docking station. That's connected to the switch, so all I do is to throw the switch and plug in the docking station - I have to unplug it and plug it in to kick the laptop into life, since the laptop has no external power switch and it sits in a small gap with its lid permanently closed (while at home). I always power laptops down fully at the end of the day, which I know not everyone does.

Works really well. Very occasionally the laptop fails to start up, and I have to open its lid and press its power button.

That's a cheaper option but I think PolarBear wanted to use Thunderbolt/USB-C out from the computers rather than HDMI?

PB, how do you want his to be configured? USB-C from each computer then HDMI from the KVM  or HDMI + USB from each computer and HDMI from the switch?

In either case the mouse/keyboard dongle will be plugged into the KVM

[grams]

The path of least resistance is to allocate the dock to the laptop and use a USB/HDMI KVM between the NUC’s own ports, the dock, and the monitor/USB dongle.

[drossall]

That's a cheaper option but I think PolarBear wanted to use Thunderbolt/USB-C out from the computers rather than HDMI?

My laptop is using a single USB-C connection to the dock. The dock is then connected to the switch via dual USB and HDMI cables, as of course is the desktop. My desktop is too ancient to know anything about Thunderbird. I don't know much about Intel NUCs, but my guess is that the Thunderbird requirement is more about the laptop?

[Polar Bear]

I've got my personal, elderly HP Windows PC (over ten years elderly, I'd think), and a work Dell 7420 laptop (my second - two successive employers happened to issue me the same model). I use this PWay switch (at least, it looks like that one).

I got work to issue me with a Dell docking station. That's connected to the switch, so all I do is to throw the switch and plug in the docking station - I have to unplug it and plug it in to kick the laptop into life, since the laptop has no external power switch and it sits in a small gap with its lid permanently closed (while at home). I always power laptops down fully at the end of the day, which I know not everyone does.

Works really well. Very occasionally the laptop fails to start up, and I have to open its lid and press its power button.

That's a cheaper option but I think PolarBear wanted to use Thunderbolt/USB-C out from the computers rather than HDMI?

PB, how do you want his to be configured? USB-C from each computer then HDMI from the KVM  or HDMI + USB from each computer and HDMI from the switch?

In either case the mouse/keyboard dongle will be plugged into the KVM

Sorry for the delayed reply.

I would prefer a thunderbolt connection from each machine to the KVM with an hdmi out to the single monitor and the Bluetooth usb-a dongle for keyboard and mouse plugged into the switch.

Thanks folks.

[Polar Bear]

"USB-C KWM" in your favourite search engine will give plenty of examples.

I've got a version of this https://itpartsmaster.co.uk/products/60263323?variant=49268550959430&currency=GBP&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&infinity=ict2~net~gaw~cmp~IT%20Partsmaster%20%7C%20Desktop%20%7C%20£100%20-%20£250%20%7C%20Low%20%7C%20Shopping%20%2724~ag~~ar~694673105992~kw~~mt~&gad_source=1&gclid=EAIaIQobChMIr6Wjt8SjhQMVJoFQBh0eOQSFEAQYBCABEgJAj_D_BwE

That looks to be perfect.  Many thanks.  👍

[drossall]

Glad you've found a good solution. I'm not quite clear where your devices will get power. In my set-up, because power and signal come over the USB-C (which is part of the point of Thunderbolt in my limited understanding), I only have one cable to unplug when I take the laptop into the office. So I'm not clear whether PaulF's approach would be an improvement for me too, by taking the Dell dock out of the equation. It's there mostly to combine the power and signal for me to achieve that single connection.

The desktop of course has its usual internal power supply, but the desktop hasn't gone anywhere for over a decade, so it could have ten connections for all I'd care.

[PaulF]

Glad you've found a good solution. I'm not quite clear where your devices will get power. In my set-up, because power and signal come over the USB-C (which is part of the point of Thunderbolt in my limited understanding), I only have one cable to unplug when I take the laptop into the office. So I'm not clear whether PaulF's approach would be an improvement for me too, by taking the Dell dock out of the equation. It's there mostly to combine the power and signal for me to achieve that single connection.

The desktop of course has its usual internal power supply, but the desktop hasn't gone anywhere for over a decade, so it could have ten connections for all I'd care.

If the laptop takes its power via USB then it will need at least two USB-C sockets, one for power and one for the KVM.

[Feanor]

I have a fairly ugly setup here with my work laptop and USC-C docking station.

The laptop takes power from a power brick on one USB-C socket.
The docking station for the monitors, KB, Mouse and ethernet plugs into a second USB-C socket.
But the docking station needs power of it's own via an olde-style Dell DC barrel-connector, it can't get it from the laptop via the USB-C cable.
(It doesn't work the other way either - the docking station won't supply power to the laptop.)

So I need 2 power bricks: USB-C to the laptop, and olde DC barrel jack to the docking station.

[Polar Bear]

Both machines have a separate power brick as does the Dell monitor. 

I've just found one of those Star Tech switches on the bay of thieves "opened but not used" on eBay for about half price.  In spite of my hatred of the bay I have taken the risk.

[Feanor]

But it does raise the question that when you have two USB-C devices plugged in together, who is the power supplier, and who is the receiver?

(I think Kim may have mentioned this before?)

[drossall]

If the laptop takes its power via USB then it will need at least two USB-C sockets, one for power and one for the KVM.

No, in the setup I described, from the laptop's point of view, everything is coming from the Dell WD19 dock, via one USB-C cable. That's the point of doing it that way. We do the same at work, but without KVM switches of course.

[Kim]

But it does raise the question that when you have two USB-C devices plugged in together, who is the power supplier, and who is the receiver?

(I think Kim may have mentioned this before?)

Yep.  There's supposed to be a sort of scissors-paper-stone negotiation in an attempt to do the Right Thing, but that doesn't work if the two devices are equal in terms of presumed sourciness/sinkiness.  At which point they'll pick a direction at random and alternate if unplugged and re-plugged.  Or if there's a non-compliant cable in the mix, possibly change behaviour depending on which way up the plug is.

All good fun until your phone discharges itself into your power bank while loitering within tent.

[PaulF]

If the laptop takes its power via USB then it will need at least two USB-C sockets, one for power and one for the KVM.

No, in the setup I described, from the laptop's point of view, everything is coming from the Dell WD19 dock, via one USB-C cable. That's the point of doing it that way. We do the same at work, but without KVM switches of course.

You’re absolutely right but I wasn’t talking about your setup rather mine and what I understood the OP’s to be

[drossall]

 

[Polar Bear]

But it does raise the question that when you have two USB-C devices plugged in together, who is the power supplier, and who is the receiver?

(I think Kim may have mentioned this before?)

Yep.  There's supposed to be a sort of scissors-paper-stone negotiation in an attempt to do the Right Thing, but that doesn't work if the two devices are equal in terms of presumed sourciness/sinkiness.  At which point they'll pick a direction at random and alternate if unplugged and re-plugged.  Or if there's a non-compliant cable in the mix, possibly change behaviour depending on which way up the plug is.

All good fun until your phone discharges itself into your power bank while loitering within tent.

I am presuming that as part of the switch the power just like the rest of the input is taken from the machine which is displaying on the monitor.

I'm sure that there is a better way to put this but that's my guess.

[Kim]

An unpowered KVM switch probably combines the power from the host busses with a couple of diodes or similar.  So it'll work as long as there's at least one host supplying power.  It's not like it needs much in the way of electrons, unless you connect something power-hungry to its USB-A ports.

[PaulF]

An unpowered KVM switch probably combines the power from the host busses with a couple of diodes or similar.  So it'll work as long as there's at least one host supplying power.  It's not like it needs much in the way of electrons, unless you connect something power-hungry to its USB-A ports.

You’re probably right.  However I’ve found it difficult to refute or prove your hypothesis. I tried unplugging both hosts and….

Let’s put it down to magic

[Kim]

Having one host disconnected is certainly a reasonable use-case (for the laptop that's not there), so it makes sense to be able to draw power from either bus.