Apple LaserWriter 12/640 PS - Manual (Page 176)

Installing RAM
Your printer comes with 4 MB of RAM installed in Bank A/B.
The table below lists RAM configurations you can use.
Amount of memory Bank C/D Bank A/B
(megabytes) (left slot) (right slot)
4 MB 0 MB 4 MB
8 MB 4 MB 4 MB
8 MB 0 MB 8 MB
12 MB 4 MB 8 MB
12 MB 8 MB 4 MB
16 MB 8 MB 8 MB
16 MB 0 MB 16 MB
20 MB 4 MB 16 MB
24 MB 8 MB 16 MB
32 MB 16 MB 16 MB
32 MB 0 MB 32 MB
36 MB 4 MB 32 MB
40 MB 8 MB 32 MB
48 MB 16 MB 32 MB
48 MB 32 MB 16 MB
64 MB 32 MB 32 MB
WARNING Refrain from handling the memory until you have put on
a grounding wrist strap. Handling the memory without wearing a
grounding strap may allow static electricity to be discharged into
the memory and damage it. If your memory kit didn’t come with a
grounding wrist strap, you can purchase one from a computer dealer.
151 Installing Options