A complete summary of slowdown devices and eunuch hardware would make a
fascinating document. Every vendor I know of at some point had the "wire
wrap" clock-x-2 upgrade, there is of course the infamous 486/487 story, and
Jon Hall used to love telling the story of the VAX backplane with the glue
in the board slots, which clever customers managed to damage and have
repaired with a non-glued-up backplane.

And on a bigger scale is the tragedy of, e.g., DECs use of its ownership of
Alpha firmware to hamstring its customer-competitors who tried to build
systems with Alpha.
"What are you doing to our Alpha customers? They're selling systems with
Alpha!"
"They're system competitors, we must crush them"

It would be neat to collect them all somewhere ...