[Official] L1Techs KVM FAQ -- Ultimate Guide & Help!

Level1_Amber · February 17, 2023, 4:26pm

No issues I can see! There is a caution for your Corsair keyboard, though.

One way to fix that is referenced in this article:

You will be able to use the keyboard, but KVM shortcuts are a little iffy.

Feel free to contact wendell at level1techs dot com for an inquiry about the KVM availability

wendell · February 17, 2023, 5:13pm

Very soon testing now

scyto · February 17, 2023, 6:57pm

I have been using the KVM with my HBR2 enabled laptop (Dell XPS 13 9300). I have read up on HBR and understand the documented limitations.

I have an issue and several things confuse me.

I had Windows 11 insider installed and it seem to be working fine with a Gigabyte M32U at 4k 60hz and a Dell PQ27516 at lower resolution than native

I had a reason to reinstall windows 11 22H2 and now I am seeing something very strange.

The M32U reports a desktop mode of 3840 x 2160, 59.95Hz. But a Active Signal of 2560 x 1440, 59…95 (it never occured to me display adapter will compress hires image to lower res output?!

The P2715Q (in portrait) repors a desktop mode of 2160 x 3840, 29.98Hz and a active signal mode of 3840 z 2160, 29.98 Hz.

Lowering the resolution on the P27115Q ro 1920x1080 doesn’t fix this (I expected it to)

I wondered if this was expected? a bug with windows 11 / intel drivers or something else.

I didn’t see this behavior on windows 11 insider, so v.confused.

edit my KVM is ’ 1.4 Display Port KVM Switch - Triple Monitor - Two Computer’
and the dell is using a dell WD19 USB dock with two DP11.4 connections for the monitors and I have the ‘laptop display’ disconnected.

scyto · February 17, 2023, 7:03pm

–disregard post–
i tried removing devices back through the USB chain

i have discovered that a 'Corsair icue Nexus is causing the Dell XP13 19300 not to post even when plugged directly into the WD19 dock, as such this is a corsair/dell issue NOT a KVM issue.

I have a 1.4 Display Port KVM Switch - Triple Monitor - Two Computer
Works fine with my ASUS motherboard PC
On my Dell XPS 13 9300 having the USB C plugged is hanging the laptop at post.

~~My USB setup is slight odd, so here goes:~~

~~8 random devices in USB3 powered hub > USB 3 A port on Gigabyte M32U > USB3 A port on KVM > USB-C port in laptop (not dock).~~

~~Any suggestions on troubleshooting?~~

scyto · February 21, 2023, 9:01pm

I changed my dock from the Dell WD 119 to a more generic USB dock and still getting this issue sometimes. I can’t figure out why the downscaling of 4K resolution into a 2k signal is happening…

TomB · February 21, 2023, 10:20pm

Got mine last week overall great but a few minor niggles: The keyboard is always powered on. Even if both machines are asleep the LEDs in the keyboard are fully lit. Probably not great for the LED longevity and a minor amount of power usage.

I’ve bought a cheap macropad to utilise the switching without needing the keyboard on 24/7 but that hasn’t arrived yet.

Can anyone recommend any USB-C → Displayport cables for this? I’m using it to swap between a desktop and a laptop. The desktop is fine but the laptop via USB-C is not.

I have this setup: 1m USB-C (Laptop) → DisplayPort (KVM) → Fibbr cable → monitor. The monitor loses signal temporarily about 3 times an hour for 5-10s while the monitor cycles through the different inputs looking for an active source. Usually when I’m trying to present something over teams at work.

I’d hoped that the Fibbr cable, which effectively acts as a signal repeater would be fine as the USB-C cable on its own works so if the signal reaches the Fibbr cable I’d have thought the signal would then be maintained but that’s not the case. I guess the extra two connections in the KVM degrade the signal further. Unfortunately I can’t find a Fibre Optic USB-C → DP cable and I’ve tried a couple of different USB-C cables with the same result.

Would a short USB-C → Displayport (female) → Fibbr cable setup be better? That’s yet another transition between connectors, and those adapters probably aren’t high quality cables themselves, so I’m reluctant to spend the money on another Fibbr cable just to test it.

scyto · February 21, 2023, 11:00pm

I found a workaround for this.

set the display resolution on the affected display to 2560x1440 - this changes the active signal resolution to 4k
change the display resolution back to 4K - all is now good

This seems to be either a KVM issue or windows 11 issue - or a combo off both as i have hit this on two display adapter types (display link and intel iris) - i have not hit this on my NVidia based machine. so YMMV.

Level1_Amber · February 22, 2023, 5:26pm

I’ve been thinking about what your issue could be. @wendell any idea?

flannelman · March 2, 2023, 8:44pm

Hi all - having some trouble picking out cables. I have the correct display port cables. I purchased the 10g 3-monitor, 2 -computer kvm switch.

3 monitor display port → 3 display port console connections
3 display port cables from PC1 → computer 1 GTX 1070
3 display port cables from PC2 → computer 2 GTX 3080TI

I also need to plug in keyboard and mouse via USB to the KVM switch. I have those connected.

I assume I need 2 USB-C cables then from PC1/PC2 USB-C to each of my computers. I have seen the recommended cables but they are very short and I need longer cables, ideally 6+ feet.

I need:
USB-C → USB-A (computer 1 only has USB-A inputs)
USB-C → USB-C

Am I understanding this right?

Any links you might have to known working cables that are 6+ feet?

bambinone · March 3, 2023, 3:55am

I’m happy to report that I’m finally up and running with my very own 4x1 L1T KVM and can answer my own question: YES! There’s no DAC in the KVM itself but you can plug your speakers into the monitor and the KVM will pass audio through from the DisplayPort inputs to the DisplayPort output.

However, there are some caveats:

Audio from our ASi MacBooks is garbled, I believe due to CalDigit SOHO USB-C Hub that we’re using for DP1.4 output. Others have reported similar issues with this dock/hub, which is too bad because it’s otherwise perfect. ~~ETA: Installing the “USB Hub Support” driver from CalDigit seems to have fixed this issue.~~ Spoke too soon, LOL. Switching away from the MacBook and back again causes the audio to stop working completely (until and un- and re-plug).
I cannot for the life of me get DisplayPort audio output working on my Radeon Pro W6400 in Ubuntu. I’ve tried adding amdgpu.audio=1 amdgpu.dc=1 to the command line and that didn’t help. I’ve also installed the “official” drivers with no change; unfortunately I’m on Ubuntu 22.10 so the “pro” drivers aren’t supported. I might try to see if I can get the installer working anyway. ETA: Yeah, that’s a no-go.

Altkey · March 27, 2023, 5:20pm

Just wanted to say I ordered the USB-C and DisplayPort cables from the Level1Tech’s store for my v1 USB-C KVM and it has removed all my intermittent issues!

My 1440p monitor runs at 144hz again without display artifacts on my Windows PC w/ RTX 2070.
I don’t have to unplug/replug the DisplayPort cable to get my Linux laptop to display to the monitor when switching from the PC.
Both the laptop and PC properly handshake with the monitor over 99hz when switching between the two without rebooting anything in the chain.
~~Laptop properly displays to the monitor when waking from sleep.~~ This appears to still be happening, less frequently though.

Brilliant products! Shipped super quick too!

Edit: Here’s the current layout
Windows PC: RTX 2070 → L1T 100cm USB-C → v1 USB-C KVM → L1T 120cm DP → Monitor
Linux Laptop: Thunderbolt 4 → OWC Thunderbolt Cable¹ → OWC Thunderbolt Hub → 20cm USB-C ² → v1 USB-C KVM → L1T 120cm DP → Monitor

¹Cable came with the OWC Thunderbolt Hub
²Cable came with this USB-C Hub from Uni.

Level1_Amber · March 27, 2023, 5:46pm

Glad that fixed your issue! Let us know if you experience any other weirdness

bambinone · March 27, 2023, 7:06pm

Disabling NKRO fixes the caps lock issue with my Keychron Q6. Pro-tip: don’t try putting the keyboard into DFU mode when it’s connected to the KVM!

Here’s my cheat sheet for getting this done under Linux. Follow at your own risk. Please note that the process is different for non-Keychron keyboards.

python3 -m pip install --user qmk

git clone https://github.com/Keychron/qmk_firmware.git

cd qmk_firmware

qmk setup # install build dependencies

# extra udev rules so linux can find the keyboard in dfu mode
sudo cp util/udev/50-qmk.rules /etc/udev/rules.d/

# choose the correct keyboard; iso has a funny enter key; encoder
# means it has a knob
KEEB=q6/ansi_encoder

# edit rules.mk and set NKRO_ENABLE = no
vi keyboards/keychron/$KEEB/rules.mk 

# make the firmware with the stock keymap and via support
make keychron/$KEEB:keychron

# flash it, but make sure to unplug it from the kvm first and plug it
# directly in the system! 
# it will keep retrying, so you can kick it off, put the keyboard into
# DFU mode, and it'll flash straight away
make keychron/$KEEB:keychron:flash

Cheers!

Level1_Amber · March 27, 2023, 7:18pm

Ah, thank you for the help and feedback!

stezleken · April 6, 2023, 5:38pm

Hi, I have few questions:

Is there a roadmap in the works for a 2 monitor USB-C KVM?
The spec breakdown shows 10Gbps USB interface (CAAB-E3112). The link, however, only states 5Gbps. Should I assume that it’s the former?
2a) If it’s 10gbps, will there be an issue trying to connect to a 2019 MBP to a 4k 120hz (ASUS PG42UQ)?

Level1_Amber · April 6, 2023, 7:18pm

Hi thank you for your question!

The USB-C variants of our DisplayPort KVMs are all 10Gbps. The CAAB-E3112 is special in that it is data & display in 1 cable. If you use the USB toggle switch that you’re referencing from the store post, the USB 3.0 port to the right will be 5Gbps. The USB-C connection itself is 10Gbps.

4K 120Hz is fine with the CAAB-3112B so long as you have proper cabling

stezleken · April 8, 2023, 6:01am

Awesome.

I have another question. This is directed more towards Wendell if he has knowledge on it.

I came across a very unique adapter in the chinese market but I could no longer find it. It’s a USB-C to either DP/HDMI with 2 USB type A (I assume it’s 3.0) attach to it. Would he happen to know anything about it? I was hoping to find that particular product again as this might solve my problem in a cost friendly manner (not requiring to get a new GPU with USB-C output for my PC) and attaching it to the Level1techs USB-C KVM.

wendell · April 8, 2023, 1:10pm

It’s not awesome though. I don’t think that answer means what you think . Stated another way… One cable only has so much bandwidth. If you want to use all your bandwidth for USB you ain’t gonna be running 4k/120 on the display side.

USBC+pd kvm is inferior to the dp1.4+USB kvm. It’s basic physics. Two cables is more bandwidth than one.

The store has a signal combiner that combines usb and displayport into USBc. But you are going to lose some bandwidth doing that . . . USBC is quite slow even at it’s max speed vs a separate dp cable and a USB cable.

stezleken · April 9, 2023, 4:25am

I understand.

If it’s running to a hub likely consisting of Keychron Q1, USB DAC, USB Microphone and wireless mouse, would it still be able to retain 4k/120? I don’t expect to plug thumbdrives to it.

The idea is to minimise cabling as much as possible as my MBP only has 2 usb-c slot. I don’t mind not getting full 4k120 on my MBP as its mainly for work, but anything would be better than what I’m currently able to drive (4k/30) via HDMI

Camm · April 11, 2023, 11:44pm

Dumb scenario time.

2 Monitors (High Resolution\Refresh Rate), 2 PC’s (Gaming + Dev) & a Laptop (only 1 PC needs high refresh, rest can be lower). Hoping to do USB C for the laptop with PD.

I’m guessing my best scenario is the DP 1.4 2 Monitor / 4 PC & use a separate dock for the laptop? Or am I missing that the USBC combiner would work in this scenario (it looked more like the other way)

Don’t have any plans for a combo USB-C/DP KVM by any chance :P?

Cheers