Apple Macintosh Performa 600 Series - Manual (Page 100)

6 Unplug the power cord from your computer.
7 Swing the handle out from its storage position. Then grasp the handle and gently but
firmly pull it toward you.
The vertical plate and the logic board to which it’s attached slide all the way
out of the computer. Carefully support the logic board as it comes out, and
put it on a stable, clean, flat surface.
What you do next depends on the type of expansion card you want to install.
93 Installing an Expansion Card