Background
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I just read this [question](https://worldbuilding.stackexchange.com/q/154420/67246) about how to get a planet to have one hemisphere with [tropical](https://sciencing.com/hot-equator-but-cold-poles-6908312.html) climate and one with polar climate. 
The (not yet accepted) [answer](https://worldbuilding.stackexchange.com/a/154421/67246) with the highest score recommends placing large enough mountains on one hemisphere, so that simply by altitude, it would be cold on the ground. 

Question
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Now I ask myself, what would have to happen to a planet so that exactly one hemisphere is (exclusively) full of high mountains whereas the other hemisphere is entirely flat? 

Related
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[This](https://worldbuilding.stackexchange.com/q/30110/67246) question might be the same as mine, just inverted. I do not know if this is the case though, and I also do not find the higher-scored answers to be answering my question.

Edit
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Since it came up in the comments: I'm only asking about landmass. The underwater topology does not factor in here, since the question linked above is framed in terms of human habitat.