The supplied LispWorks (64-bit) for Macintosh images are now universal binaries which run the correct native architecture on PowerPC and Intel-based Macintosh computers by default. This was already true for LispWorks 5.0 (32-bit) for Macintosh but was not possible at the time of the initial LispWorks 5.0 (64-bit) for Macintosh release.
A running Lisp image only supports one architecture, chosen when the image was started. On a PowerPC based Macintosh, this is always the PowerPC architecture. On an Intel-based Macintosh, for 32-bit LispWorks it can be either the native Intel architecture or the PowerPC architecture (using Rosetta), while for 64-bit LispWorks it is always the Intel architecture.
Functions such as
create an image containing only the running architecture and functions that operate on fasl files such as
only support the running architecture.