What does the "In-line" in SIMM and DIMM memory mean?
The &quot;in-line&quot; is about all the contacts being in a straight line on the edge of the PCB.
The SIMM has only actually one set of contacts: the contacts on either side of the PCB are connected.
You can see that on a photo of the slot; there is only one contact for both sides.

source: wikimedia user Wolfgang &quot;Darkoneko&quot; ten Weges
On a DIMM, both sides of the PCB carry one line of different contacts:

source: wikimedia user Project Keil