You can change the drive current with the Current Strength setting in the Assignment Editor.

The drive current value that can be set differs depending on the Column/Row, so please search for the keyword ”Programmable Current Strength” in the Device Handbook of the ULR link below and refer to it.

https://www.altera.com/en_US/pdfs/literature/hb/stratix-iv/stx4_siv52001.pdf

When I run the High Performance Controller TCL command, it is set to “MAXIMUM CURRENT”.
If you compile in this state, the drive current will be 8mA for Class I of SSTL-15 and 16mA for Class II.
When changing the drive current value from this value, it is recommended to thoroughly verify whether there is no problem in operation.