My Symbolics 3640 Lisp Machine, a model introduced in the mid 1980s had 20 MB RAM and 200 MB virtual memory on one or two disks. The OS was already a 50 MB image. The memory used by Lisp was typically much larger than the available (and/or affordable) RAM.
Access times were far from constant.
A full Garbage Collection over virtual memory took 30 minutes. That's why it had extensive support for incremental garbage collection, copying GC, manual memory management, areas for various data types, ephemeral GC with hardware support, cdr-coded lists, various types of multidimensional arrays, graphics cards with special video memory, 36 bit memory with additional ECC, ...
Before saving a new Lisp image to disk, one was using a special command to reorder objects in memory to optimize access times. That command also took 20-30 minutes.
Lisp Machines like this were developed because Lisp systems on Mainframes or Mini Computers were thrashing the machines during GC and making performance hell for Lisp users and other time sharing users. Thus a personal machine was needed where the memory and CPU belong to one user. They were among the very first commercially available GUI based personal workstations in 1981.