You should be fascinated hitting the power button on your computer. Every boot on an x86 machine iterates through the entire sequence of computing evolution in a few milliseconds: Stage 1: 16-bit Real Mode, acts like an 8086 from ~1978. 500ns (ish); about 15-30 instructions. Goal of this stage is to create a writeable stack+heap. Stage 2: 32-bit Protected Mode, acts like a 386 from ~1985. Tens of millions of instructions; takes forever on DDR5 /w memory training. Temporarily uses L2/L3 “cache-as-ram” to kickstart main ram (Intel calls this NEM). Stage 3: 64-bit Long Mode, acts like AMD64 from ~2003. Hundreds of millions of instructions; enumerate pcie devices, gpu, bootloader, etc. Stage 4+: Secondary core wakeup. Every *single* core has to go through the same process, but by this point it’s faster because Main RAM is warmed up. Stage 2 is just so neat man. Quite literally the same concept as an APU/cart start. Use the smaller motor (L2/L3) to kickstart the main turbine (Main Ram) and execute the training process. Is that not just the coolest thing? Next time I’m annoyed waiting at the DDR5 training process, I’m going to imagine it’s spinning up SR71 turbines.