The PTC does not allocate power of I/O elements in the FPGA core die uniformly; rather, power contributions of I/O elements are allocated according to their physical locations in the die. The thermal solver uses this power allocation to calculate the temperature map of the die.
If the I/O bank locations are not specified correctly, the power of I/O elements may get allocated incorrectly, to a single bank or to the wrong banks. In such scenarios, the thermal solver still produces a result; however, due to the increased power density, a hot spot may incorrectly occur in the I/O section and erroneously increase the maximum thermals.
The I/O Bank Allocation feature allows you to specify location of I/O elements to banks, thus ensuring that power contributions of I/O banks are allocated correctly, and that there is no miscalculation of thermals.