Atari PC Owner's Manual page 62

3. Carefully turn the computer right side up while holding the
bottom panel in place. Set the computer down. Remove the
cover by lifting it straight up.
4. The chip sockets are in an opening, or hatch, in the metal
shield that protects the motherboard. Remove the two screws
on the hatch cover with a small Phillips screwdriver. Hook your
finger through the hatch cover hole, gently lift it off, and lay it
on top of the shield. Take care not to disconnect the speaker
and wire attached to the motherboard and the underside of the
hatch cover.
Installing the Chips
The hatch can hold four 64 kilobyte x 4 RAM chips. You should
install all four chips. You can also install any of the following Intel
numeric data processors:
8087 (5 MHz)
8087-2 (8 MHz)
8087-1 (10 MHz)
Note: If you install the 5 MHz numeric data processor, you will
not be able to use the PC's turbo mode.
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Speaker and Wire