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 ...