IBM Aptiva Handbook page 102

Your system board has two system memory module sockets:
DIMM 0, and DIMM 1. These sockets hold Dual Inline
Memory Modules (DIMMs) that contain 3.3V single- or
double-sided synchronous DRAM (SDRAM). You can install
up to a maximum of 256 MB of system memory into these
sockets. For information about supported memory
comfigurations, see "Memory module placement" on page
A-1.
Note: You must always have memory installed in DIMM 0.
The following figure shows the location of the DIMM sockets
on the system board.
9-6 Chapter 9: Adding and replacing system board components
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To install a DIMM:
1.
Locate the memory retaining clips at both ends of the
socket. Pivot the memory retaining clips outward.
2.
Locate the two notches on the DIMM and the two tabs
on the socket. Align the DIMM with the socket. Make
sure the nothes and tabs align.
3.
Press the DIMM into the socket until the clips lock into
.
the DIMM
The DIMM socket is slotted to ensure proper
installation. If you insert a DIMM but it does not fit
Note: easily into the socket, you may have inserted it
incorrectly. Turn the DIMM around and try to insert
it again.