Dell OptiPlex E1 Reference And Installation Manual page 97

Because of the height of the hard-disk drive, expansion-card connector PCI1 is
limited to an 8.75-inch-long card.
LED
ISA2
ISA1
HDLED
connector
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To install an expansion card, follow these steps:
See Chapter 3, "Using the ISA Configuration Utility," for instructions.
NOTE: If you install a PCI or Plug and Play expansion card, your system automati-
cally performs any required configuration tasks during the boot routine.
See the documentation that came with the expansion card for information on
configuring the card, making internal connections, or otherwise customizing the
card for your system.
Save the screw to use when installing the expansion card later in this procedure.
P1
PCI2
PCI1
Installing System Board Options 6-3