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OpenBSD Unsupported Video Signal

Spent a couple hours this evening on the #openbsd irc channel troubleshooting a display issue. Couldn't figure this one out though we had fun trying!

Specs:

USB Stick and Openbsd 6.2 Image

  • Known good,
  • Openbsd image installed successfully from this USB, to a virtual env on a separate device, using these instructions

Desktop computer

  • Motherboard, 64bit Intel processor
  • On-board graphics only
  • Currently running Ubuntu 16.04.03 Server
  • BIOS (legacy enabled) set to boot USB first

Monitor

Symptoms

  • Start computer on Ubuntu server, displays just fine, no issues
  • Boot to Openbsd USB stick, bios screen runs, self check passes then monitor displays "Unsupported Video Signal". This is not an Openbsd message, but rather from the monitor itself.

Done so far

  • Cleanly formatted USB (under supervision)
  • Installed from USB to virtual env on separate device, no issues, loads Openbsd just fine.
  • Boot computer to Ubuntu, display works perfect
  • Boot computer to Openbsd USB, display shows error message above.
  • Unplug and replug VGA cable
  • Power off, power on monitor

Suspicions - Pg. 88 of the Toshiba monitor manual shows a table of Acceptable Signal Formats for PC IN. My hunch is the graphics driver is incompatible with this monitor. Toshiba manual

Questions

  • Is there anything I can do to make this monitor work with a new Openbsd 6.2 install?
  • How can I check Openbsd monitor compatibility before embarking next time?
Solution

  • Ubuntu has KMS support for the nVidia graphics card but OpenBSD only has support for the old UMS driver. The OpenBSD kernel (probably, I'm not sure) is using 640x480 as resolution and the Linux kernel is using the highest resolution supported by your monitor.

    You have two options to "fix" the problem. Install OpenBSD on another computer or with a different monitor (you can also use a laptop with a USB<->HDD adapter), when the installer ask if you want graphics support (or something like that, I don't remember), reply yes. Finish the installation and reboot. Then move the HDD to the original computer and power on the machine. You will see the same message but at some point the system will run xenodm (a graphical launcher for X11 sessions, like xdm), then the monitor will work fine. Unfortunately, you can't see the console messages.

    Don't change xorg.conf, your problem is not only related to the monitor. Another option (quite better, imho) is to buy a cheap used ATI graphics card and just install OpenBSD. The ATI graphics cards are fully supported (except the newest ones) and have KMS support. You will only see the message during two or three seconds and after of that, you will see the console. Maybe you will need run the installer on a different computer or with a different monitor, but everything will work fine after of that.

    Anyway, OpenBSD uses only a standard mode for the basic console. It doesn't make weird unsupported things. So, probably your monitor has some kind of problem with the lowest VGA resolution/frequency. The problem is that the OpenBSD kernel can't change to a higher resolution during the boot process because it doesn't support the nVidia cards at the kernel level. It uses a userland driver for the nVidia cards, like the Linux/BSD/Unix traditionally used to use.

    If you have an old (like 10 years or so) Linux LiveCD/installer, try to run it on your computer. You will see the same problem.