Someone suggested (off-list) that you should remove any expansion cards,
which is always good advice when troubleshooting an early crash.
E.g. Linux doesn't have support for the WGS 95 PDS card fitted to some
Quadra 950 machines (unfortunately). But if that was your problem, I'd
expect 2.6.29 would not boot either.
Where did you find the 2.6.29 kernel binary? If it is a mainline kernel,
we may be able to solve this with git bisection.
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