Any idea why undoing (ctrl+z) something as simple as scaling an icosphere just kills blender? My fans spin up like crazy. Is this a bug or just how it is? I'm pretty new.

  • $\begingroup$ What's your spec? It might be the problem. I have 4 GB of RAMs, GeForce GT 720, and i3 CPU and they work fine $\endgroup$ Commented Nov 22, 2020 at 23:54
  • $\begingroup$ i5 6600K, 16GB Ram, GTX1080 $\endgroup$ Commented Nov 25, 2020 at 15:04

1 Answer 1


Consider Blender undo/redo as an automately backup system, they read all data in previous step and load all of them directly. (2.8x)
(2.9x add some optimized method to it, see the link below)
(2.7x and below is another system)

Handling time will depend on your memory accessing speed and your data 'size'. In some situation, undo/redo can be bulky:

  • Large amount of meshes vertices
  • Low available system memory (RAM) causing constantly memory swap
  • Dirty blender file with lots of abandon/orphan data chunks leaved in data
  • Cumulative memory leak in process when running Blender (restart Blender)

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