Comet KVM: USB Input Fails Post-Login + Phantom Display Issue in Windows

KVM
1

Hi all,

I’m using a GL‑RM1 Comet KVM with the Power Control Board on a production PC (dual-boot Linux Mint and Windows 11 Pro). I’ve run into a set of serious issues:

:small_blue_diamond: Issue 1: USB Input Fails After Login

  • Keyboard and mouse work fine at the OS login screen.
  • Once the desktop appears (Linux and Windows), neither device responds.
  • The host’s cursor is visible, but remote input is completely unresponsive.

:small_blue_diamond: Issue 2: No BIOS/GRUB Access

  • The Comet KVM only starts displaying video after the OS boots.
  • I cannot remotely access the BIOS or GRUB menu — the reason I bought the product and essential for troubleshooting.

:small_blue_diamond: Issue 3: Windows Phantom Display Bug

  • In Windows 11, opening Settings causes it to appear on a phantom monitor that is:
    1. Not visible on the host PC’s monitor.
    2. Not visible on the remote KVM session.
  • This makes the Settings app completely inaccessible from both the host and the remote console.

:white_check_mark: What I’ve Tried

  • Enabled “Legacy USB Support” in BIOS.
  • Connected KVM dongle to a rear USB 2.0 port.
  • Updated to the latest Comet firmware.
  • Adjusted monitor configurations on the host system.

:hammer_and_wrench: Questions for GL.iNet Engineers & Community

  • Is there a firmware fix (even beta) for USB-HID passthrough issues?
  • How can I force BIOS/GRUB visibility remotely?
  • Can EDID or display mirroring on the Comet be adjusted to prevent the Windows phantom display problem?
  • Has anyone else experienced this?

This feels like a broader firmware or USB handling issue, and I hope GL.iNet can prioritize a fix.

Thanks!

— Manuel Uribe

System Information:

Motherboard: Z790 Taichi Carrara (ASRock)
Windows 11 Pro Version: 24H2 Build 26100.4061
Linux Mint: 22.0 "Wilma"; Cinnamon desktop
KVM Version: 1.3.1 release 2

2

Update:

I managed to solve issues 1 & 3. My PC has an RTX 2070 Super GPU and a purpose add-on board for keyboard and mouse that came with the motherboard, and the KVM was plugged into both.

SOLUTION:

I plugged HDMI into the motherboard's HDMI. Since my Intel 13900K CPU includes on-board graphics, that did that trick with issue 1.

Similarly, connecting the KVM's USB keyboard and mouse emulator to a port directly on the motherboard solved issue 3.

Issue 2 remains outstanding:

I still can't see the BIOS nor GRUB. The video only comes in once the OSs are at the login page.

3

Generally, computers output the BIOS screen to the highest priority display: dedicated graphics card > integrated graphics, DP > HDMI. If multiple monitors are connected via HDMI, there's also an internal priority within HDMI.

This is why, generally, you can't see the BIOS screen on laptops, as the built-in laptop display usually has the highest priority.

Regarding your problem:

If you can accept having the BIOS screen only on COMET, then increase COMET's priority: If your monitor has a DP port, buy a DP to HDMI adapter to increase COMET's priority. If you're currently connected to integrated graphics, try connecting to the dedicated graphics card.
If you need the BIOS screen on both your local monitor and COMET: You'll need to buy an HDMI 1-to-2 splitter (assuming your monitor has an HDMI port), and then connect both your monitor and COMET to this splitter. However, this will limit high refresh rate monitors to only 60Hz.

4

There are also some BIOS systems that support switching output displays via shortcut keys. But it is usually only found in notebooks

5

Using the Win + P shortcut, you can easily set up screen mirroring in windows