Can't run over 512x384 using Ubuntu on Bondi iMac 266MHz!!

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Joined: Oct 16 2005
Posts: 1

I have installed Ubuntu on a Bondi 266MHz iMac with 256MB. Install was sucessful--I am no newbie to installing Ubuntu (at least on x86 boxes) and, even if I was, it's SO easy that I'd get thru it anyhow.

Here's my problem: the machine, while running Gnome, will only let me have a maximum resolution of 512x384 with a refresh rate of 75Hz. As you can figure, this resolution is absolutely unusable on the iMac's small monitor (I like the refresh rate, tho!). I don't care if I have to give up the refresh rate--I need to run the machine at AT LEAST 800x600, 1024x768 if possible. I can't see anything! Color depth doesn't matter either; as long as I can get 8-bit color its cool. The Mac USED to let me run MacOS at 1024x768x256. I don't get it--duh....

I have gone over Ubuntu's config files with a fine-toothed comb; nowhere can I find a place that specifies that my monitor should run at 512x384. All xorg entries are either 800x600-1024x768. When I switch into Ubuntu "text mode" on another tty (CTRL-Opt-Fx) you can tell that the characters are being rendered at AT LEAST 1024x768? What's the deal?

Can ANYONE help me with this? I have checked EVERY FAQ, tutorial, man page, etc. to find an asnwer--I'm hoping that one of my new virtual friends on applefritter can give me a hand. Can you help me?

Thank you for reading this extended rant, and hope SOMEONE out there who's smarter than me (c'mon, there's LOTS of you...) can give me a hand. Thanks again friends.

-Ron Damato

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Jon's picture
Joined: Dec 20 2003
Posts: 2804
Have you tried the [url]www.u

Have you tried the (I'm registered as JDP over there) But, as for your troubles, what driver is it set to use? Do you login with GDM or does it auto-login? If GDM, then does that show up as a better res? What version of Ubuntu?


I am not in this world to live up to other people's expectations, nor do I feel that the world must live up to mine. - Fritz Perls

Eudimorphodon's picture
Joined: Dec 21 2003
Posts: 1203
Nothing Specific, however...

I can't say much without seeing the situation in person, and it's been a long time since I've done Linux on my iMac, however...

1: Are you running X using the framebuffer driver, or the native Mach64 driver? Look for the section "Device" in /etc/xorg.conf. What does the "Driver" line say? ("ati", "vesa", or "something else")

2: Set up Ubuntu to *not* start X when it comes up. (I've never used it in particular, so that's an exercise for the reader. Redhat-based Linuxi make that decision by setting the default runlevel in /etc/inittab to "5". You can get a text-only login by setting it to "3". Perhaps Ubuntu's the same.) That done, trim down the "Modes" entries in your "Screen" -> "Display" to "1024x768", and start with "startx".

A: If it fails to start with "no screens found" then you have a driver problem. Look again to see if it's trying to use "fb" or "vesa" as the driver.

B: "No valid modes found" means the xorg driver is probing your video card looking for an automagic list of modes and is failing to find anything fitting "1024x786". Fixing that will probably call for adding flags in the "Device" section to tell it to not do that autoprobe.

C: If you get a black screen I'd be willing to bet you need to add modelines for the iMac's screen. It doesn't use "normal" SVGA/XGA refresh rates, and at least back when I was running Yellow Dog on the little monsters you needed to use the appropriate modelines if you wanted to use the internal monitor. It would *not* automatically figure it out. (Luckily Yellow Dog's included Xfree86.conf already had the modelines in them.)

D: If you still get 512x384, look in the conf file for the word "doublescan" somewhere, probably as an "Option". If it's there, kill it.

Just some suggestions, anyway.


Joined: Nov 2 2005
Posts: 1

The iMac Tray loaders only had 2MB of VRAM built on the board.
Adding more VRAM fixes the 512x384 issue.

I added 4MB to my 233mhz Bondi and now I'm able to view at 1024.
The iMac 333mhz had 6MB.

So if you have a 233mhz or 266mhz iMac add more VRAM!

Jon's picture
Joined: Dec 20 2003
Posts: 2804
Also, there are many threads

Also, there are many threads in the lists. Here is one about problems on first gen iMacs. There are more, but the main issue seems to be that Breezy doesn't setup X correctly on trayloaders. It really needs to be said which versionof Ubuntu teh OP is using for a correct diagnosis, as different problems and solutions only work for certain releases of Ubuntu.

The VRAM may be an issue, but the OP states that it worked in MacOS, so it should work in Linux too, if setup correctly.

And I guess I'm replying to the wrong post too... Smile


I am not in this world to live up to other people's expectations, nor do I feel that the world must live up to mine. - Fritz Perls

Joined: Dec 20 2003
Posts: 25
I had the same problem on my beige G3

Use a text editor to take a look at this file:


Look for -

Section "Screen"

Four lines down you will see -

Default Depth 24

Change this to 8 or 16 and save the file.

The next time that you reboot you should have more resolution options.

Note: I think that you have to be root to edit this file.