Solved
Web page inconsistency STM32F7x5 caching
https://www.st.com/en/microcontrollers-microprocessors/stm32f7x5.html
Top of page talks about I/D cache being 4K+4K
on sub pages becomes 16K + 16K for 32K total
https://www.st.com/en/microcontrollers-microprocessors/stm32f765vi.html

