'Special' software configurable memory regions are still appearing in new embedded designs. ARM9-ARM11 has had Tightly-Coupled Memory (TCM) to "hold critical r

'Special' software configurable memory regions are still appearing in new embedded designs. ARM9-ARM11 has had Tightly-Coupled Memory (TCM) to "hold critical routines, such as interrupt handling routines or real-time tasks," "scratch pad data" and interrupt stacks. This has now appeared in the latest (M7) ARM Cortex designs. The fact is that frequently it is critical to optimize that 0.1% and reserve predictable, fast memory for it. So that's the lesson learned at least for the highly successful embedded ARM platform.