GIGABYTE AMD Socket AM2 Processor Motherboard GA-M55SLI-S4 - Manual (Page 31)

Hardware Installation - 31 -
English
19) CI (Chassis Intrusion, Case Open)
This 2-pin connector allows your system to detect if the chassis cover is removed. You can
check the "Case Open" status in BIOS Setup.
Pin No. Definition
1 Signal
2 GND
1