In addition to what cjbprime mentioned... There's a lot going on in a modern (or even one from 10 years ago) SoC with regards to power management. Just the pr

In addition to what cjbprime mentioned... There's a lot going on in a modern (or even one from 10 years ago) SoC with regards to power management. Just the processor cores themselves can run at different voltages and frequencies, and these are tied to the software workload. And then you've got the big / little stuff from ARM now, which is an asymmetric multiprocessor, and which cores you use depends on the workload. At how it works and the interface to it changes from vendor to vendor, sometimes from chip to chip. So it usually isn't implemented all that well, nor is it maintained for very long either. If (big if) we had more standardized interfaces to this functionality, we could use common drivers that can be upgraded independently. Like I said, the desktop people may not realize how easy they've got it, where most things are accessed via a standardized bus interface (PCIe or USB). There's no virtuous cycle of software and interface re-use, like there is in desktop land.