[SOLVED] monitor says "invalid mode", won't show console

Dave Cohen · 2012-01-18 07:20:01

I have a fancy flat panel TV monitor that has all sorts of inputs, include a VGA. I'm trying to plug an Arch box into that VGA port for what you might call a set-top box or you might call a computer with a big monitor.

Trouble is about halfway through booting, Arch tries to change the resolution or something, and the monitor switches to an error screen saying simply "invalid mode". Before this happens, I can see some of Arch's boot messages, but it goes by too fast to see exactly what they are. Note that I'm just trying to get to a console, not starting X. I've played with grub line settings like "vga=ask", I don't think that's the problem as I see the system start to boot.

If I plug into a regular computer monitor, the system works fine. I can get to a console and then start X. There's just something wrong when trying to display on the large monitor, and I'm not sure how to start troubleshooting this.

... I just tried booting the machine with a Knoppix CD... it also resulted in the monitor switching to "invalid mode". So not Arch-specific, apparently, but still I hope experts on this forum can help me out. Thanks in advance.

Last edited by Dave Cohen (2012-01-18 18:31:46)

ewaller · 2012-01-18 07:36:29

I think you are trying to turn the wrong (virtual) knob.

This might help: https://wiki.archlinux.org/index.php/KMS#Forcing_modes
YMMV.

You are fighting with KMS, not the initial console setting. I presume this happens after the kernel loads at about the time the initscripts start running.

Dave Cohen · 2012-01-18 10:09:42

I was unable to set the "video=...." parameter. I checked my kernel log but couldn't find anything like "VGA-1" or "DVI...". So I guessed some values for video= but none had any effect. Still thanks for the pointer.

I found both "nomodeset" and also "i915.modeset=0" as things to append to the kernel line. They behaved identically: I was able to boot to the console (it filling only a fraction of the screen, centered). Unfortunately when I started X, it just looked like garbage. Not quite static, but no better. If you know what I mean.

I haven't configured an xorg.conf, I was hoping not to need it (and don't, on a regular monitor), but I may give that a shot, tomorrow.

And I probably should have mention sooner my graphics card:

[dave@boxey2 ~]$ lspci | grep VGA
00:02.0 VGA compatible controller: Intel Corporation 82845G/GL[Brookdale-G]/GE Chipset Integrated Graphics Device (rev 01)

Last edited by Dave Cohen (2012-01-18 10:11:16)

Dave Cohen · 2012-01-18 18:31:07

I read a little more about forcing a resolution and with some success. I left out the device and simply added:

video=1360x768

to the kernel line. It is working, at least enough to get me to the console. I still have trouble starting X.

I expermented by starting up a laptop, then plugging it into the VGA port. xrandr showed a number of possible modes. The highest was 1920x1080. Unfortunately I couldn't make that work. I always get "Invalid mode" on the monitor. But other values like 1360x768 did work, so that's what I've just added to the kernel line.

Although I'm puzzled why I can't get the max resolution out of this monitor, I'm marking this as solved (although I still need to set up X so that it picks a valid mode).

Arch Linux

#1 2012-01-18 07:20:01

[SOLVED] monitor says "invalid mode", won't show console

#2 2012-01-18 07:36:29

Re: [SOLVED] monitor says "invalid mode", won't show console

#3 2012-01-18 10:09:42

Re: [SOLVED] monitor says "invalid mode", won't show console

#4 2012-01-18 18:31:07

Re: [SOLVED] monitor says "invalid mode", won't show console

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