Not dead, but just injured.
Replaced two 312M RAM cards with one faster 2G RAM card.
Old RAM defective; tech told me that its speed was actually mismatched to
the rest of the system, slowing it down. Of course "defective" was the
crucial issue, not speed.
Machine works fine now, running devuan ascii.

Next plan: upgrade to current chaemera in stages

Thank you for all the testing suggestions. They really helped narrow down
the problem. Not mention moral support.

-- hendrik