System-Board Memory - IBM PS/2 65 SX Hardware Maintenance Reference

3.3.1 System-Board Memory

The Model 65 SX has at least 2MB of memory installed at the time of
shipment. An additional memory-module kit can be installed in the second
memory-module connector on the system board.
memory capacity is 4MB (2MB memory module kits installed in memory-module
connector 1 and 2). A memory-module kit must be installed in memory
module connector 1. The system can support a total of 16MB of memory.
IBM PS/2 Model 65 SX HMR
System-Board Memory
The maximum system board
3.3.1 - 1