Frequently (I work on large SOCs) it's less risk and more flexible to let software do boot. For example, there is some initialization step in the way between t

Frequently (I work on large SOCs) it's less risk and more flexible to let software do boot. For example, there is some initialization step in the way between the big core and the instructions, and it is deemed easier/less risky to let software perform this initialization rather than do it in hardware and not have a fallback in case of hardware bugs. Or, if you have the fallback, then you've just reinvented the simple-core boot mechanism so you might as well ditch the hardware work. I hate this trade-off because it means so much irritating work for the software engineer and frequently has downstream impact on other parts of the system (e.g. does PCIe link come up in time?) but the risk of silicon problems drives this design decision.