Compact Flash Adapter
The Compact Flash (CF) adapter supplied with MISE is inserted into an IDE box header; you could use an IDE cable and electromechanical hard drive instead if you wanted. You'd need an IDE cable with the "key" pin (pin 20) unblocked--many cables have that pin blocked to ensure the cable is inserted correctly, but MISE uses it to power the CF adapter. You'd need an external power supply for the IDE drive.
The adapter has 3 LEDs on the front side: red (power), yellow (hard drive activity), and green (CF card inserted).
The adapter has two CF sockets, for Primary and Secondary devices. The Primary CF device (the one that LDOS boots from) is inserted into the CF socket on the side with the LEDs. The Secondary device (if any) is inserted on the other side of the adapter.
The jumper labeled CF1 on the adapter will, if shifted to the rightmost position, swap the Primary and Secondary devices.
With two CF cards inserted into the adapter, you may notice that the yellow LED is illuminated when reset to the MISE is removed (usually when the Expansion Interface is first switched on.) This is normal--the signal used on the IDE interface to indicate the presence of the secondary device is shared with the activity indicator. Once the MISE is booted, the yellow LED will function normally.
Important: The pins of the CF sockets are extremely delicate. If you feel any resistance when trying to insert or remove a CF card stop immediately. Check carefully for bent pins. Trying to force a CF card in or out can cause the pins to become unseated from the back of the socket! If the socket is simply too tight, a gentle rocking motion can sometimes help to insert or remove a CF card. The connectors for the Secondary cards tend to be particularly tight.