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Thread: Ubuntu 8.10 on an iMac G5 PPC? You betcha!

  1. #11
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    Re: Ubuntu 8.10 on an iMac G5 PPC? You betcha!

    Quote Originally Posted by inigomontoya View Post
    Scaling is not an issue for me as I'd rather have as much performance as possible with 0 latency between switches.
    In that case, you'd want cpudyn as the frequency scaler, since it has very low latency between switches as compared to powernowd - even when you get powernowd working. Just install cpudyn from the repos and see. A couple of guys who do audio editing etc tried it and it works very well. It saves about 10 watts of power when idle and shouldn't affect your operations. Check it out. Cpudyn is ideal for non-smp boxes, although it works to a fashion with multiple cpu's.

    The only thing that is really bothering me is that the LCD displays 16bit colors when set to 24bit. I know it has something to do with this screen only having 6 bits per pixel.
    I think you may be confusing color depth with hardware specs - in this case it is because our lower-cost flat panels really only have 6-bit hardware, as compared to the higher quality ones that do 8-bit - again nothing to do with color depth. If you are running an nvidia card, you can force that option which is normally off (from the nv man-page)

    Option "FPDither" "boolean"
    Many digital flat panels (particularly ones on laptops) have only 6 bits per component color resolution. This option tells the driver to dither from 8 bits per component to 6 before the flat panel truncates it. Default: off.
    I don't think this applies to super displays like the Apple Cinema displays with 8-bits, but for our iMacs, we are down in the 6-bit area. And, I don't think the opensource ati driver can do this. It does make a difference, even on my non-ppc boxes that have nvidia cards. But this is a hardware spec, and not a color-depth issue.

    Getting back to color-depth, it is strange that your machine doesn't seem to want to do 24-bit color depth. How did you determine that? Oh, one last check - does your screen-resolution gui show 1680x1050 at 60hz?
    Last edited by stream303; January 18th, 2009 at 08:40 PM.
    20" G5 iMac - AMD64 HP desktop
    http://www.ppclinux.info/

  2. #12
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    Re: Ubuntu 8.10 on an iMac G5 PPC? You betcha!

    Quote Originally Posted by stream303 View Post


    I think you may be confusing color depth with hardware specs - in this case it is because our lower-cost flat panels really only have 6-bit hardware, as compared to the higher quality ones that do 8-bit - again nothing to do with color depth. If you are running an nvidia card, you can force that option which is normally off (from the nv man-page)


    I don't think this applies to super displays like the Apple Cinema displays with 8-bits, but for our iMacs, we are down in the 6-bit area. And, I don't think the opensource ati driver can do this. It does make a difference, even on my non-ppc boxes that have nvidia cards. But this is a hardware spec, and not a color-depth issue.

    Getting back to color-depth, it is strange that your machine doesn't seem to want to do 24-bit color depth. How did you determine that? Oh, one last check - does your screen-resolution gui show 1680x1050 at 60hz?
    When set to use 24-bit color lots of color banding is apparent as if i'm running in 16-bit mode, that's what i mean. It is running in 24-bit but it doesn't look that way. So is OSX dithering this before it's displayed? I saw no color banding while running OSX. I have a 17inch imac so the resolution is 1440x900. It is correctly displayed in the GUI.

  3. #13
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    Re: Ubuntu 8.10 on an iMac G5 PPC? You betcha!

    Everything technically is working well, it would appear that my one of my issues is also with the display.

    1. I don't know how to describe this, but here it goes. My screen is wrapped about 1/4 of an inch to the right, where the last tiny bit of the right side of my screen is displayed on the left side. I haven't been able to figure out what that is about.

    2. Networking drivers are present, and I can get online... I configured eth0 manually. However, when I go thru any gui networking config it shows that i am NOT connected. Also, my wifi won't connect... which is a relatively minor issue, but I'd like to have the networking fixed up.

    Otherwise, I'm really excited to get this iMac back alive!

  4. #14
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    Re: Ubuntu 8.10 on an iMac G5 PPC? You betcha!

    Quote Originally Posted by g0bez View Post
    Everything technically is working well, it would appear that my one of my issues is also with the display.

    1. I don't know how to describe this, but here it goes. My screen is wrapped about 1/4 of an inch to the right, where the last tiny bit of the right side of my screen is displayed on the left side. I haven't been able to figure out what that is about.

    2. Networking drivers are present, and I can get online... I configured eth0 manually. However, when I go thru any gui networking config it shows that i am NOT connected. Also, my wifi won't connect... which is a relatively minor issue, but I'd like to have the networking fixed up.

    Otherwise, I'm really excited to get this iMac back alive!
    The first thing I did was get the newest ati drivers from git, http://cgit.freedesktop.org/xorg/driver/xf86-video-ati/

    After that I did the first round of updates through update-manager. I enabled the Broadcom driver in the restricted driver manager then rebooted. Upon rebooting I saw that my wireless wasn't working quite right so I compiled the latest stable kernel 2.6.28. Then everything worked.

  5. #15
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    Re: Ubuntu 8.10 on an iMac G5 PPC? You betcha!

    Thanks for the tips -- i'll check out the ATI drivers.

    Once I try out the new kernel I'll see how the hardware responds. If i understand correctly, the wifi drivers are different than the eth0 drivers. I'll have to look into this more tho.

  6. #16
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    Re: Ubuntu 8.10 on an iMac G5 PPC? You betcha!

    Quote Originally Posted by inigomontoya View Post
    When set to use 24-bit color lots of color banding is apparent as if i'm running in 16-bit mode, that's what i mean. It is running in 24-bit but it doesn't look that way. So is OSX dithering this before it's displayed? I saw no color banding while running OSX. I have a 17inch imac so the resolution is 1440x900. It is correctly displayed in the GUI.
    I wonder what driver xorg is really picking up? Does the log /var/log/Xorg.0.log show ati, radeon, etc, or just something like fbdev?
    20" G5 iMac - AMD64 HP desktop
    http://www.ppclinux.info/

  7. #17
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    Re: Ubuntu 8.10 on an iMac G5 PPC? You betcha!

    Quote Originally Posted by g0bez View Post
    1. I don't know how to describe this, but here it goes. My screen is wrapped about 1/4 of an inch to the right, where the last tiny bit of the right side of my screen is displayed on the left side. I haven't been able to figure out what that is about.
    Welcome to my world.

    I have only seen this effect on my G5 iMac running the opensource nvidia "nv" driver. Is yours also using nv, and what size is the screen? Mine is the 20" 1.8ghz model:

    http://www.everymac.com/systems/appl...ndex-imac.html

    Just so we don't get our wires crossed, which model do you have?

    I have spoken to the folks at freedesktop.org, and they confirm that this slight shift to the right is due to a recent commit to nv that fixed some other user's problems with flat panels - unfortunately, that messed it up for us. So it is upstream of ALL the distros. If it drives you nuts, only Feisty and below (or Debian Etch 4.0rX) use the older nv driver which didn't have this "fix".

    2. Networking drivers are present, and I can get online... I configured eth0 manually. However, when I go thru any gui networking config it shows that i am NOT connected. Also, my wifi won't connect... which is a relatively minor issue, but I'd like to have the networking fixed up.
    I think the big issue here is that if you are going to manually configure your network by manually editing the /etc/network/interfaces file, you need to remove Network Manager. Or, even if using the standard Gnome network gui setup, NM has to go. If you DO use network manager, do NOT try to manually configure your /etc/network/interfaces file, or use the gui in System > Network. That drove me nuts for quite awhile. I chose to rip out Network Manager.

    I'm very interested to see if you are using something other than a 20" G5 iMac running nvidia.
    20" G5 iMac - AMD64 HP desktop
    http://www.ppclinux.info/

  8. #18
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    Re: Ubuntu 8.10 on an iMac G5 PPC? You betcha!

    Quote Originally Posted by stream303 View Post
    I wonder what driver xorg is really picking up? Does the log /var/log/Xorg.0.log show ati, radeon, etc, or just something like fbdev?
    The log shows that it is indeed using the radeon driver. Strange thing about it is, like with everyone else, if i take a screenshot and view it with another machine that displays 24 bit color correctly, there is no banding. I would guess that means that it's rendering in 24-bit, but the LCD is not displaying it that way. It was my understanding that the Dac6Bit option would dither the image to 6 bits from 8 before it was sent to the display eliminating color banding.

  9. #19
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    Re: Ubuntu 8.10 on an iMac G5 PPC? You betcha!

    This caught my eye - can you disable DRI and see if that makes a difference? :

    http://forums.gentoo.org/viewtopic.php?t=469455

    The warning in that xorg.conf mentions not being able to use 24 bits if dri is enabled, and although it is for a different card, and much lower graphics memory, I wonder if that is worth trying just to see...
    20" G5 iMac - AMD64 HP desktop
    http://www.ppclinux.info/

  10. #20
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    Re: Ubuntu 8.10 on an iMac G5 PPC? You betcha!

    Quote Originally Posted by stream303 View Post
    This caught my eye - can you disable DRI and see if that makes a difference? :

    http://forums.gentoo.org/viewtopic.php?t=469455

    The warning in that xorg.conf mentions not being able to use 24 bits if dri is enabled, and although it is for a different card, and much lower graphics memory, I wonder if that is worth trying just to see...
    I disabled DRI and it still shows alot of color banding. I'm using this as a test image: http://web.comhem.se/zacabeb/reposit...ectrum_rgb.png

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