In STM32f105rbt6 as i am using external crystal of 8MHz. i tried to config it at 72MHz using (PLL) STMcube ide. what will be the maximum toggle frequency of a gpio.

[waclawek.jan]

If driven by hardware peripheral, e.g. a timer, the pin may toggle at maximum possible speed, i.e. being set as 1 during 1/72MHz and as 0 during 1/72MHz, resulting in output frequency of 36MHz.

However, if you toggle the pin as a GPIO Output by sofware, the resulting frequency will probably be significantly lower.

JW