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The Peculiarly Quiet Decline and Fall of the KVM

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Re: The Peculiarly Quiet Decline and Fall of the KVM

#51

Post by NameOpenSource »

OliverJones wrote: post #34
sdfjkl wrote: post #25

KVM switches used to be a huge and super important (and expensive) thing in rack server farms back when every rack or every few racks had a pull-out tray with a keyboard and a monitor. Technology moved on. First the tray and monitor disappeared with KVM-over-IP, which saved many trips to the server room. Then the KVM switches themselves disappeared, as manufacturers integrated out-of-band remote access into the serve…

Yes, no doubt that rack-based kvm stuff disappeared. It was awful: hard to rig, hard to use with confidence. (Confidence? "Wait, wait, am I talking to data2 or web4 or what?) KVM was a just-barely-competent solution to a hair-on-fire (=== must-solve-now) problem.

"What ? this was the production server ?... woops"

Re: The Peculiarly Quiet Decline and Fall of the KVM

#52

Post by Jaruzel »

sdfjkl wrote: post #25

KVM switches used to be a huge and super important (and expensive) thing in rack server farms back when every rack or every few racks had a pull-out tray with a keyboard and a monitor. Technology moved on. First the tray and monitor disappeared with KVM-over-IP, which saved many trips to the server room. Then the KVM switches themselves disappeared, as manufacturers integrated out-of-band remote access into the serve…

> Cut a HDMI cable in half and splay it out, then try switching that to another display. See what happens.

If you took an ancient (but still available to buy) 25-pin 'parallel port' 4-port switch box with a rotary dial:

https://photography-909a.kxcdn.com/product-images/03292/600/...

And wired up the HDMI of two machines to output ports 1 & 3[1]. Then wired up the HDMI to the display to the input port (so effectively using the switch 'backwards'). As you are just simulating unplugging and re-plugging in the HDMI cable from each machine, via the switch, then surely this would work?

There would be a bit of delay after switching as the HDMI/HDCP handshake completes, but unless you are switching every few minutes it should be usable?

If it does work, then you've got 6 pins in the switch left to play with which could be used to switch usb devices (via a downstream hub)

I've not done this, but have thought about it for a while now.

----

[1] Not ports 1 & 2 as you want to ensure total electrical isolation between the devices during switching.

Re: The Peculiarly Quiet Decline and Fall of the KVM

#53

Post by daemin »

theothertom wrote: post #45
daemin wrote: post #9

The main thing that has pissed me off with technologies like DisplayPort and HDMI is that I cannot actually turn my monitors off when I'm not using my computer. With DVI I could turn the monitors off and the desktop and applications would stay where they were. With HDMI/Displayport it considers the monitor disconnected, hence re-adjusts the desktop and moves everything around. I would love an option that I could swit…

I've never really understood the desire to use the button on the display to turn off monitors - does allowing the monitors to be switched off by the OS not solve basically the same problem ?

I leave my PC running 24/7 pretty much, so at night I want the monitors turned off so it doesn't illuminate the whole living room (which I can see from the bedroom - it is a small apartment).

I used to turn them off with the button on the monitor (when all my monitors were DVI), so if the mouse was moved by accident during the night it wouldn't wake the monitors up. Right now I have to let it go to sleep normally, and then hope there isn't some strange vibration that is big enough to trigger a wake.

Edit: Better language and more info.

Re: The Peculiarly Quiet Decline and Fall of the KVM

#54

Post by Jaruzel »

Fnoord wrote: post #48
sdfjkl wrote: post #25

KVM switches used to be a huge and super important (and expensive) thing in rack server farms back when every rack or every few racks had a pull-out tray with a keyboard and a monitor. Technology moved on. First the tray and monitor disappeared with KVM-over-IP, which saved many trips to the server room. Then the KVM switches themselves disappeared, as manufacturers integrated out-of-band remote access into the serve…

Anecdotal, I still use a KVM, for a specific use case. My PC has 2 monitors. My 1st monitor is standard usage, but my 2nd monitor is also used by my partner's PC. If she wants to use her computer, she gets the 2nd monitor (and the speakers) but otherwise I got a 2nd monitor to use. Practically, it saves me from having to use another set of speakers (you would not use 2 sets of speakers at the same time and I usually…

You are not alone in this. For years my Partner and I had separate machines on a KVM. It was only when our Daughter moved out and her desk became free in our study that we no longer needed this setup.

Re: The Peculiarly Quiet Decline and Fall of the KVM

#55

Post by beojan »

blauditore wrote: post #11
beojan wrote: post #7

Earlier quoted context omitted.

What if it physically unplugged the HDMI connection, and reconnected it to the other device? It wouldn't be quite as seamless since the initialization process would be repeated, but it would work .

Not even physically, but just redirecting the raw signal to another device should work. Maybe artificially break it for a second or so to better simulate plugging out and back in. I can't see how the actual endpoints could tell a difference between that and manually un- and re-plugging into a different device.

That's what I meant. Electrically, it's identically to unplugging from one device and plugging into the other.

Re: The Peculiarly Quiet Decline and Fall of the KVM

#58

Post by taneq »

daemin wrote: post #53
theothertom wrote: post #45

Earlier quoted context omitted.

I've never really understood the desire to use the button on the display to turn off monitors - does allowing the monitors to be switched off by the OS not solve basically the same problem ?

I leave my PC running 24/7 pretty much, so at night I want the monitors turned off so it doesn't illuminate the whole living room (which I can see from the bedroom - it is a small apartment). I used to turn them off with the button on the monitor (when all my monitors were DVI), so if the mouse was moved by accident during the night it wouldn't wake the monitors up. Right now I have to let it go to sleep normally, an…

Every monitor I've owned since the early 2000s will switch itself off (or at least go into a standby state where the screen is entirely off and there's a tiny blinky LED indicating that it's still powered) after a period of inactivity. I know some monitors never give up waiting for a signal but at this point maybe it'd be simpler to treat yourself to a new monitor?

Edit: Oh, you're talking about things waking your computer up? Maybe turn off 'wake on USB'? Although that's less convenient otherwise. I know when my desktop computer is fully hibernated, mouse motions don't wake it but button presses do. And you can get into this state (assuming Windows 8+) by right clicking on the Windows icon / 'start' button and selecting 'sleep'.

Re: The Peculiarly Quiet Decline and Fall of the KVM

#59

Post by gm-conspiracy »

Jaruzel wrote: post #52
sdfjkl wrote: post #25

KVM switches used to be a huge and super important (and expensive) thing in rack server farms back when every rack or every few racks had a pull-out tray with a keyboard and a monitor. Technology moved on. First the tray and monitor disappeared with KVM-over-IP, which saved many trips to the server room. Then the KVM switches themselves disappeared, as manufacturers integrated out-of-band remote access into the serve…

> Cut a HDMI cable in half and splay it out, then try switching that to another display. See what happens. If you took an ancient (but still available to buy) 25-pin 'parallel port' 4-port switch box with a rotary dial: https://photography-909a.kxcdn.com/product-images/03292/600/... And wired up the HDMI of two machines to output ports 1 & 3[1]. Then wired up the HDMI to the display to the input port (so effectively…

I think the real isssue is with HDCP.

The output device "ensures" the display device is authorized via a key to output.

So, you would need an intermediary device that would accept any incoming signal, while also having a legit handshake with the output device.

So, as you switch "inputs", there is no additional authorization required, because the output device does not detect any changes.

Re: The Peculiarly Quiet Decline and Fall of the KVM

#60

Post by cesarb »

Jaruzel wrote: post #52
sdfjkl wrote: post #25

KVM switches used to be a huge and super important (and expensive) thing in rack server farms back when every rack or every few racks had a pull-out tray with a keyboard and a monitor. Technology moved on. First the tray and monitor disappeared with KVM-over-IP, which saved many trips to the server room. Then the KVM switches themselves disappeared, as manufacturers integrated out-of-band remote access into the serve…

> Cut a HDMI cable in half and splay it out, then try switching that to another display. See what happens. If you took an ancient (but still available to buy) 25-pin 'parallel port' 4-port switch box with a rotary dial: https://photography-909a.kxcdn.com/product-images/03292/600/... And wired up the HDMI of two machines to output ports 1 & 3[1]. Then wired up the HDMI to the display to the input port (so effectively…

Would it have enough bandwidth? High speed connections have some careful engineering (for instance, maximum distance without a twist on a differential pair), that I doubt that ancient box has.

Also, there are sequencing requirements. Look carefully at a USB-A plug, and you'll see that the power and ground traces are longer than the data traces: when plugging the USB cable, the power is connected first, before the data; when unplugging, the order is reversed. HDMI probably has similar requirements, perhaps with more steps. Again, I doubt that ancient box can do that.

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