Motorola 68230 - Vanguard 300 DSU/CSU Operator's Manual page 64

U73 and U69 are marked on the surface of the motherboard, just below the SIMM
slots. The SIMMs are different sizes, so you cannot install the SIMMs in the
incorrect slots.
Procedure to Install SIMMs
Use the following procedure to install SIMMs.
Step Action
Insert the SIMM into a slot at a slight angle as shown in 4-14.
1
Press the SIMM into the socket.
2
Make sure it locks in place with the locking tabs.
3
Figure 4-14. SIMM Installation