Radeon HD 4800 CrossFire User Manual page 19

Chapter 2: Hardware Installation
HD4870X2
D13 and D14: Identify the EXT_12V connector for inserting Power cable.
D15: Identify the thermal /FAN failure.
D5 and D7: VDDC of GPU 1 and GPU 2 core voltage failure.
When the graphic card works normally the five LED don't light up.
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