Problem with scrambled screen in Linux

[evilcartman]

I've had the same desktop computer for about five years, although in that time I've had a change of graphics card from an Nvidia Geforce to an AMD Radeon.

When I have installed Linux Ubuntu in the past, it always worked pretty much straight out of the tin without needing too much tweaking.

However, when I have tried to reinstall Linux in more recent times, the screen gets scrambled like this:



I have tried various versions of Ubuntu and also Mint. In fact I just downloaded the latest version, Mint 14, and still had the same problem.

I enquired on various Linux support forums about it and never even had a response. This is something that people complaining about Windows and moving to Linux need to take note of - it's fine when it's working, or if there's a problem that the 'community' can help you with, but sometimes they can be stumped and then you're on your own.

However, it's now occurred to me that it may not be the graphics card that is the problem. It could be the monitor. It has a native resolution of 1680x1050 and I suspect that Linux may not support this straight out of the box. I can see the instructions in writing at the beginning when Linux starts to boot up, it's what happens to the screen after booting is completed.

I only have the one monitor working at the moment, so may have to borrow one off someone to test this theory out.

If it is the monitor - and I strongly suspect it is now - can any Linux gurus help with any configuration text files I need to create to tell Linux the resolution is 1680x1050?

[Riz]

Re: Problem with scrambled screen in Linux

Eeek!

Not really had to troubleshoot Radeon drivers/display issues, not not sure how much help I can be.

As far as I recall the correct drivers should cope with even odd display resolutions. You may however be able to tweak a custom xorg.conf file to force certain resolutions.

What is the model of the graphics card?

I note that a quick Google shows a few reports of people getting coloured stripes on certain ATI/Radeon cards.

For example. https://wiki.archlinux.org/index.php...with.2Fout_KMS

[Riz]

Re: Problem with scrambled screen in Linux

Also, there are 2 drivers for ATI/radeon cards if I recall correctly. The open source driver, and the closed source ATI propitiatory driver.

Now, I'm not sure which Mint tries to use out of the box, but whichever it is it may be worth trying to switch to the other if you see what I mean.

[evilcartman]

Re: Problem with scrambled screen in Linux

Yeah, I'm aware that there have been issues with ATI/Radeon cards but thought it would have been addressed by now. I had heard of this issue, so assumed that was the problem here - but having loo0ked again at that screen, I would say my problem here is actually the monitor having an unusual default resolution. It's one that I got second hand and doesn't have a manual, so I can't find a way of setting it to alternative resolutions. The buttons don't seem to help.

The specific model of the card is AMD Radeon HD 6670. It's not a model that Mint reports as having any particular issues.

[Riz]

Re: Problem with scrambled screen in Linux

Open source driver howto --> RadeonDriver - Community Ubuntu Documentation

ATI binary driver howto --> BinaryDriverHowto/ATI - Community Ubuntu Documentation

[Riz]

Re: Problem with scrambled screen in Linux

OK. Are there any obvious error messages in the xorg log once you have got to that screen?

less /var/log/Xorg.0.log

and scroll through the log

I also note this in the man page for the xorg.conf settings.

http://manpages.ubuntu.com/manpages/...ml#contenttoc4

Option "PanelSize" "string"

Should only be used when driver cannot detect the correct panel size. Apply to both desktop (TMDS) and laptop (LVDS) digital panels. When a valid panel size is specified, the timings collected from DDC and BIOS will not be used. If you have a panel with timings different from that of a standard VESA mode, you have to provide this information through the Modeline. For example, Option "PanelSize" "1400x1050" The default value is none.

[evilcartman]

Re: Problem with scrambled screen in Linux

OK. Are there any obvious error messages in the xorg log once you have got to that screen?

less /var/log/Xorg.0.log

and scroll through the log

I also note this in the man page for the xorg.conf settings.

http://manpages.ubuntu.com/manpages/...ml#contenttoc4

Thanks for this, rizzle.

I have my new kit now, which has my Windows 8 setup on it. I have tried various new flavours of Linux on this combo and still get that weird scrambled screen.

I have all the ingredients needed to build a new Linux box from my old box, mobo, DVD writer, some old drives and my old Nvidia card (which definitely worked with Linux). Unfortunately the old box is playing silly buggers and keeps cutting out within seconds at power up, and you have to keep persisting until it eventually allows you to boot up. I'm presuming the PSU is sh*gg*d. So until I can replace that, my plans for reinstalling Linux on that machine are in limbo.

I could try putting the Nvidia card in the new machine and seeing what happens, but in the meantime I have found an old monitor that I had used successfully with Ubuntu on the old machine - trouble is that I haven't found its power adapter yet. When I do, I could test my monitor theory.

[Riz]

Re: Problem with scrambled screen in Linux

Well, I would try in order...

1) The different monitor.

2) Switching display driver. Open source --> AMD flglrx/catayst or vice versa depending on what you have now.

3) Trying to write a custom xorg.conf if (2) doesn't solve the problem.

[Riz]

Re: Problem with scrambled screen in Linux

I would add that's just my best guess. I haven't done any troubleshooting with Radeon cards under Linux.

When buying a new lappy etc, I tend to make sure I buy what I know (well 99% sure) will work.

Radeon/Nvidea are a lot better than they were, but can still be a bit flaky at times if reports are to be believed.

So I try to stick to Intel graphics on laptops which are at least rock solid stable for all but the most bleeding edge hardware. Not the fastest option, but I'm not bothered about daftly good graphics for gaming or other such, so it does the job.

[Riz]

Re: Problem with scrambled screen in Linux

Another possible thing to try if you are using a ubuntu based distro is to activate these ppas.

X Updates

or

xorg-edgers

Both contain updated xserver and drivers compared to the one that come with a standard install. In some cases they may contain fixes that sort your problem.

[evilcartman]

Re: Problem with scrambled screen in Linux

Well, I would try in order...

1) The different monitor.

2) Switching display driver. Open source --> AMD flglrx/catayst or vice versa depending on what you have now.

3) Trying to write a custom xorg.conf if (2) doesn't solve the problem.

OK, sorry for the delay in responding. I still haven't got around to trying the old monitor yet. However, I am typing this on the current computer in Linux Mint 14.

No, it isn't a successful installation just yet. I tried the "compatibility mode" option from the 'live DVD' and everything looks nice and clear from here. It did initially show the same corrupted screen as all the other attempts to install Linux with this card/monitor combo but somehow managed to pull itself together and come up with a viewable display.

So it is certainly possible - but do you have any clues how I can work out what the 'live DVD' did to make the screen viewable and how I can port these settings over to an actual installation?

You mention "Trying to write a custom xorg.conf" and switching the display driver - but I'm clueless on how I go about doing these tasks when the screen is corrupted and I can't see what I'm doing. Presumably I need to put the settings into a text file somewhere on the HD, which will then enable Linux to boot up correctly on this setup. I'm not sure how I go about doing that though.

[Riz]

Re: Problem with scrambled screen in Linux

I shall have to have a ponder on that. e.g. try to find out what different kernel boot parameters and other things the "compatibility mode" uses.

[Riz]

Re: Problem with scrambled screen in Linux

Oh, and for the record. which "edition" of Mint 14 are you using?

i.e. Mate, Cinnamon, XFCE, KDE?

[evilcartman]

Re: Problem with scrambled screen in Linux

XFCE 64-bit.

The monitor does auto config, incidentally, so that shouldn't be the cause of the problems, it probably still is something to do with the graphics card and not having the correct drivers available by default.

[Riz]

Re: Problem with scrambled screen in Linux

Well, looks like the "compatibility" mode adds the xforcevesa option to the boot command line.



That forces the graphics card to run using the generic vesa driver rather than the Radeon one.

vesa is basically a bare bones driver that works with the core functions of most graphics card, but won't run any higher end graphics/acceleration. In other words, the display will work but anything that uses more than very basic graphics will either be dog slow or not work at all.

So perhaps try adding that to the boot line of your installed system? You should have the option to edit the boot line somewhere on the bootloader screen.

If your system works with that setting, then you know it is likely a Radeon driver issue.