IBM PS/2 80 Hardware Maintenance Reference page 28

IBM PS/2 Model 80 HMR
Memory Requirements and Limitations
4.1.3 Memory Requirements and Limitations
The system board does not have to be fully populated before you add 80386
Memory Expansion Adapters, and each memory-expansion adapter does not have
to be filled to capacity before you add another memory-expansion adapter.
Whenever memory is added or removed from the system, the set configuration
program must be run.
¦ Copyright IBM Corp. 1990
4.1.3 - 1