A little over 10 years ago I was doing some very resource-constrained embedded programming. We had been using custom chip with an 8051-compatible instruction s

A little over 10 years ago I was doing some very resource-constrained embedded programming. We had been using custom chip with an 8051-compatible instruction set (plus some special purpose analogue circuitry) with a few hundred bytes of RAM. For a new project we used an ARM Cortex M0, plus some external circuitry for analogue parts. The difference was ridiculous - we were actually porting a prototype algorithm from a powerful TI device with hardware floating point. It turned out viable to simply compile the same algorithm with software emulation of floating point - the Cortex M0 could keep up. Having said all that though: the 8051 solution was so much physically smaller that the ARM just wouldn't have been viable in some products (this was more significant because having the analogue circuitry on-chip limited how small the feature size for the digital part of the silicon could be). Obviously that was quite a while ago! But even at the time, I was amazed how much difference the simpler chip made actually made to the size of the solution. The ARM would have been a total deal breaker for that first project, it would just have been too big. I could certainly believe people are still programming for applications like that where a modern CPU doesn't get a look in.