You can install LispWorks 8.1 in the same directory as previous versions such as LispWorks 8.0. This is because most of the 8.1 files are stored in a subdirectory called lib/8-1-0-0.
Binaries produced by cl:compile-file in previous versions of LispWorks do not load into a LispWorks 8.1 image. You must recompile all your code with the LispWorks 8.1 compiler.
Release Notes and Installation Guide - 25 Feb 2025 19:14:05