Computer Grey Goo

Take a Grey Goo scenario with out-of-control technology, but have it eat most known computing basics - silicon transistors, vacuum tubes, etc. Maybe it's a holdover from a previous civilization on your planet, an out-of-control weapon of some kind.

So your planet has to look for alternate technology, but if they try anything easy/standard it turns to mush in a few days, vastly limiting computing capability.

Computer Grey Goo

The problem with messing with laws of physics is everything tends to tie into everything else. Which is why something like changing the speed of light messes with atomic structures, so it's really hard to think of a simple change that will only make minor modifications like this.

Instead, take a limited Grey Goo scenario with out-of-control nanotech, but have it eat only most known computing basics - silicon transistors, vacuum tubes, etc. Maybe it's a holdover from a previous civilization on your planet, a weapon of some kind that ended up spreading everywhere.

So your planet has to look for alternate technology, but if they try anything easy/standard it turns to mush in a few days, vastly limiting computing capability. This allows mechanical computer, but anything standard won't be viable.