Would it be by way of some hard coded cpu bootrom or by way of some ROM boot loader or some embedded firmware ? Anyone ?
The CPU is installed on a platform board along with a chipset component. The power up sequence starts with instructions from within the chipset that cause the CPU and memory power rails to come up. A power good signal is then passed to the CPU where there is an embedded controller that takes care of waking up the CPU and its cores. There is also a whole sequence of handshaking that goes on from that point that is involved with deasserting the reset of the CPU and getting its busses initialized so that it can start to fetch its first instructions (BIOS) and initialize memory and all the I/O devices.