I-cache was just one example that most people find easy to understand. The original paper on compressed instructions claims 25-30% reduction in total instructi

I-cache was just one example that most people find easy to understand. The original paper on compressed instructions claims 25-30% reduction in total instruction size. A typical small M0 microcontroller will have something like 4-32kb of RAM and 32kb to 1MB of flash storage. No matter how you slice it, saving 30% of your instruction space is a HUGE deal. Even with EEPROM (usually used for flash memory) taking just 2 transistors per bit, we're still talking about compressed instructions taking up 200 bits, 40 bytes, or just TEN 32-bit instructions in your flash memory. With that 30% optimistic number, any program with more than 30 instructions will have a net benefit from compressed instructions. Even my very pessimistic 10% number would mean just 100 instructions before you break even.