10G KVM improvments beyond USB3 Bandwidth

[symexec]

I’ve been rocking a Dual Display (DP1.4) + 4PC Level1Techs KVM for a few years now. And while overall it has been an amazing tool, it has not been without it’s issues (which I go into more detail with below).

However I recently picked up a Single Display + 2PC 10G model for another project, and the issues I’ve had with my setup have completely vanished when dropping this device in. Issues completely unrelated to the USB3 5Gbps / 10 Gbps links back to the host.

TLDR: If you’re trying to decide between the 5Gbps and 10Gbps models of the KVM, it might be worth picking up the 10Gbps even if you don’t actually need that extra bandwidth.

Now to wait for the 4PC variants of the 10Gbps KVMs to become available …

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DP Troubles

Driving a display at the absolute limits of what DP1.4 can handle is super iffy. I use a AW3821DW, which is capable of 3840x1600@144Hz@8bit (and no DSC support). But I’ve never been able to run that display through the KVM at those limits. I’ve had to stay at or below 120Hz@10bit. If I attempt any higher, I’ll have snow artifacts or consistent screen flickering.

And even at the reduced refresh rate, it’s not perfect. I’ll frequently have the flickering/artifacts after switching inputs, and have to juggle the inputs a few times until it’s stable. Switching to FIBER DP cable (from PC to KVM, and KVM to Display) does dramatically reduce the likelihood of these issues, but even that does not let me drive the monitor at it’s full capabilities.

Additionally, even at the reduced refresh rate, I have to be selective about the input ports. PC1 and PC2 will not work without serious flickering/artifacts at anything above 100Hz. Also have an issue where the display on those inputs simple will not get any input during POST and boot, until after the OS has loaded. Even if I get my system to boot directly into UEFI menu, I’ll get not display output. Makes tweaking bios super annoying…

Last year I picked up a Single Display (DP1.4) + 2PC KVM (5G model) for my spouse’s setup. Works perfectly fine for her setup, but I tested it with mine and had to exact same issues noted above.

Doesn’t seem likely that I have a faulty unit. That said, I did run into another user on reddit that had same exact DP issues with a Level1Techs KVM and the AW3821DW. He was able to return the AW3821DW and picked up the LG38" display that uses the same panel, and that works for him without issue. So maybe the issue is with some Dell funkiness.

USB HID Troubles

For the most part USB HID devices through the KVM has been completely fine, other than some expected and documented issues. I’ve been using the G502 Lighspeed for years without issue. I’ve seen some reports of users having issues with Logitech’s device that use the lightspeed wireless protocol, but it’s worked great for me through the KVM.

However back in September I picked up the new G502 X Plus mouse, and that’s a different story. When connect through a HID port, the device will stop responding either after an indeterminate period of time, or after I switch inputs. The only way to restore connectivity is to either unplug/replug the dongle, or run Logitech’s ‘Onboard Memory Manager’ utility, which seems to wake it back up.

This is easly worked around by just using the USB3 ports for the mouse. This complicates my setup through, as I liked to keep these ports ‘stuck’ to a particular PC and not follow the selected input.

[wendell]

@symexec

I use a AW3821DW, which is capable of 3840x1600@144Hz@8bit (and no DSC support)

Technically that’s against spec; DP must support dsc in certain circumstances. Macs ignore DSC also, until apple had to support it for their 5k display, which they technically now do dsc in some but not all scenarios.

That particular display is not field upgradable; you must send it back to dell and there is a huge swath of variability

From a kvm design standpoint, the actual PCBs cause the kvm to get taller as you add more monitor capabilities because each board is generic and standardized. this helps us keep costs as low as possible. Each board is its own mezzanine for a specific function. The lowest level is logic/control and USB, next level is display, next level 2nd monitor, next level 3rd monitor, next level 4th monitor.

Aside from the overall general evolution and tighter quality control over the years, and the pandemic causing supply chain issues, and the desirability to be able to swap between whatever components are available for a reasonable price without being to dependent on one specific IC packaging, GENERALLY the displayport pcbs are the same between 5 and 10g models of a given run/era.

That display is kind of the devil though. G9 neo had a lot of the same issues fortunately as of firmware 1008 most of those issues are resolved.

Even something like… mac don’t support dsc right. If you toggle between a dsc and a non dsc signal… does the display re-handshake right? It doesn’t on the g9 or the alienware. Do I have to try to scream into the void, electronically, when switching inputs in that scenario to make the monitor say “wait a minute, what just happened? let’s renegotiate” even if it means everyone else has to wait an extra half second for no reason when switching inputs? Do we introduce code to behave differently depending on detected monitors?

this, my friends, is a quick path to insanity. Guiding princple of the kvm here is keep it simple, stupid. as simple as it can possibly be.

@symexec

So maybe the issue is with some Dell funkiness.

can 100% confirm.

Also, not all fibbr cables are created equal. Digital signal in an analog world… sometimes the analog world bleeds through despite our best efforts. You’d be surprised if you keep playing the cable lottery how the situation can change.

@symexec

new G502 X Plus mouse

I’ll have to test this. We did add some special stuff to the firmware when the new lightspeed stuff showed up to work better with it on hid ports. Complicating matters was logitech apparently made some mistakes themselves? There was a sort of “run 0” of lighspeed parts… I bought a bunch of stuff on greymarket to try to test lightspeed stuff and got a bunch of lightspeed gear with the serial numbers all marked out. And got it working with those.

turns out those had lots and lots and lots of bugs and logitech never really sold those? or if they did they recalled them and just replaced them? few customers got these too… imagine my legendary troubleshooting rep points increase from the following convo:

“dear sir my logitech lightspeed is not working, it is doing this thing where the rgb turns on and off and right click doesn’t register? it works fine if I plug it straight in”

“ah, good sir, flip your mouse over. has someone sharpied out the serial #? Does it say A01 on the sticker in the upper right? Yes, it turns out you’ve been sold a gray market light speed and that one while the software works and picks it up has certain hardware bugs that make my life hard. if you got it from logitech directly, its under warranty, and the’ll replace it but otherwise its grey market and the retail ones don’t do that.”

(time passes)

“I got one from office depot and it works perfectly now. (thanks).”

But I learn from these experiences so we can make things better every iteration. I’m not merely selling a product… I am scratching an itch. My own way of screaming back at the void… its compulsive, really… when experiencing the edge cases in daily life…

anyway, thanks for buying lots kvms