Hi, how exactly cpu becomes clever from just be a piece of silicon? Initially its just a piece of stone and metal with photolithography on it, and then somehow it piece of stone starts understand commands, how exactly first instruction is loaded to a piece of stone?
In: Engineering
The CPU is designed to, from a total power loss or a reset, start in a specific mode and start loading instructions from what it sees as “memory” starting from a specific address. The CPU specifications and/or its manufacturer will specify what this is. Beyond that, it does just start running instructions immediately in the usual way.
When I say “specific mode”, for example modern CPUs can run in several modes such as 16 bit, 32 bit and 64 bit and many variants and so on. At power-on which mode it is in will always be the same.
Whoever makes the circuit board the CPU is installed into is responsible for having a storage chip on the board with code already saved onto it, ready to go and available to the CPU as part of its “memory”/RAM. In the old days this was often a removable chip to allow upgrading by literally swapping it out, or re-programming it with a device designed to do it. These days it’s stored on flash memory, like an SSD, but on the board itself.
That code usually goes by the name of “firmware”, or on PCs people will call it the BIOS sometimes.
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