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