Some autobump tests. The cave wall is a procedural material with displacement and bump.
RAM usage:
Autobump off, displacement size 1px: 11,6 GB
Autobump off, displacement size 4px: 3,4 GB
Autobump on, displacement size 4px: 5,2 GB
Note that the quality of autobump off 1px is _similar_ to the quality of autobump on 4px, while the RAM usage is 11,6 GB vs 5,2 GB.