A device configured to connect an external graphic processing unit to a computer apparatus for adjusting power consumption of the external graphic processing unit according to different voltage sources and comprising: a first voltage input configured to receive power from a first voltage source; a second voltage input configured to receive power from a second voltage source, wherein the second voltage source is the computer apparatus and wherein the voltage of the first voltage source is higher than the voltage of the second voltage source; a voltage output coupled to said first and second voltage inputs (160, 170) and configured to supply power to the external graphic processing unit; a determination module coupled to the voltage output and configured to determine whether power to the external graphic processing unit is supplied by the first voltage source or the second voltage source of the different voltage sources according to a comparison result of the output voltage for the external graphic processing unit and a default reference voltage, wherein the determination module is configured to determine that the power to the external graphic processing unit is supplied by the first voltage source if said output voltage is higher than or equal to the default reference voltage, and the determination module is configured to determine that the power to the external graphic processing unit is supplied by the second voltage source if said output voltage is lower than the default reference voltage; and a control unit coupled to the determination module, wherein the control unit is configured to control the external graphic processing unit to remain in a normal speed operation status when the power to the external graphic processing unit is determined to be supplied by the first voltage source, and to remain in or convert to a low speed operation status when the power to the external graphic processing unit is determined to be supplied by the second voltage source; wherein an operation speed of the low speed operation status is lower than the operation speed of the normal speed operation status. a first voltage input configured to receive power from a first voltage source; a second voltage input configured to receive power from a second voltage source, wherein the second voltage source is the computer apparatus and wherein the voltage of the first voltage source is higher than the voltage of the second voltage source; a voltage output coupled to said first and second voltage inputs (160, 170) and configured to supply power to the external graphic processing unit; a determination module coupled to the voltage output and configured to determine whether power to the external graphic processing unit is supplied by the first voltage source or the second voltage source of the different voltage sources according to a comparison result of the output voltage for the external graphic processing unit and a default reference voltage, wherein the determination module is configured to determine that the power to the external graphic processing unit is supplied by the first voltage source if said output voltage is higher than or equal to the default reference voltage, and the determination module is configured to determine that the power to the external graphic processing unit is supplied by the second voltage source if said output voltage is lower than the default reference voltage; and a control unit coupled to the determination module, wherein the control unit is configured to control the external graphic processing unit to remain in a normal speed operation status when the power to the external graphic processing unit is determined to be supplied by the first voltage source, and to remain in or convert to a low speed operation status when the power to the external graphic processing unit is determined to be supplied by the second voltage source; wherein an operation speed of the low speed operation status is lower than the operation speed of the normal speed operation status.