Comment 31 for bug 87652

Probably a quick and dirty fix is to just install a past ubuntu kernel deb, like this one:

http://packages.ubuntu.com/edgy/base/linux-image-2.6.17-11-powerpc

Otherwise, I followed these instructions, roughly, with a 2.6.19.7 kernel from kernel.org:

http://ubuntuforums.org/showpost.php?p=1359285&postcount=5

but doing a
make pmac32_defconfig
instead of the g5_defconfig on that thread.

Then I made sure to uncheck the module
PowerMac dma sound support

so the sound configuration looks like this:

http://ubuntuforums.org/showpost.php?p=2572887&postcount=30

Otherwise, it's a stock pmac32_defconfig kernel config.

There's probably a more proper ubuntu-way of compiling your own kernel, but this works.

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FWIW I tried the newer 2.6.21 kernel, and varying releases of alsa with no luck. So seems that something happened in the 2.6.20 kernel.