Was there an IBM computer where a memory upgrade was flicking a switch?

[Darren_Garrison]

Here’s one example:

Energy needs of UNIVAC type computers

From the wiki: The Cyber-72 had identical hardware to a Cyber-73, but added additional clock cycles to each instruction to slow it down. This allowed CDC to offer a lower performance version at a lower price point without the need to develop new hardware. Don’t tell me nobody tried to hack that!