Making STM32 Ethernet Work With Cache Enabled

This article explains how turning on CPU cache on modern STM32 chips can silently break Ethernet DMA and cause weird, hard-to-debug network issues. It walks through why this happens and shows simple, practical ways to fix it by keeping Ethernet buffers out of cached memory or properly syncing the cache so the CPU and DMA see the same data. Overview The world of microcontrollers was peaceful and predictable until someone introduced advanced interconnect buses. Unhappy with that, someone else introduced caches.