I succesfully booted the Powerstack with this initrd: http://people.debian.org/~luther/d-i/vmlinuz-2.4.22-powerpc-prep.initrd
It boots without problems... It downloads the installer components without any problems but then it complains about not finding the cdrom drivers. In the console i can see that it does not find the drivers for my scsi controler .. and does not find the drivers for the network card.. but it downloaded the installer components only seconds before.. and you can ping to the network card from an external comp without problems... The missing modules are: tulip for the networkcard, and sym53c8xx for scsi... Has anybody else tried to install sarge on a powerstack?
