As discovered previously the overclocking program ftune performed better when USB cable is plugged in, it was not sure back then whether the data link or the extra power supply contributed to the performance boost. It is now confirmed power supply alone will do the trick.
The test is carried out using a Casio Basic program running a parameter searching for a logistic regression equation using the Nelder-Mead algorithm. A portable power bank is plugged to the USB port of the Casio fx-9860gII with ftune.
The tested portable USB power bank comes with 4000mAh capacity and 1A output, and is fully charged. There are 4 blue LED indicator lights.
The power bank is turned on.
The test result shown that the program run with power bank finished in 46 seconds, and the one without finished in 93 seconds.