All Raspberry Pi boards have status LEDs positioned in one corner next to the 3.5mm audio jack and USB port(s).
The Model B has five status LEDs whereas the Model A has two. The Model A has PCB labels for all the LEDs but the three network related LEDs are not populated.
The following photo shows the five status LEDs on a Raspberry Pi Model B Rev 2.0 board (Note the mounting hole not present on the original Model B Rev 1.0 devices).
Revision 1.0 Boards (Model B) labels are :
Revision 2.0 Board (Model A & Model B) labels are :
The LEDs have the following meanings :
- ACT – D5 (Green) – SD Card Access
- PWR – D6 (Red) – 3.3 V Power is present
- FDX – D7 (Green) – Full Duplex (LAN) connected
- LNK – D8(Green) – Link/Activity (LAN)
- 100 – D9(Yellow) – 100Mbit (LAN) connected