[als0]

> Regardless of where the CPU begins getting its instructions, the beginning point should always be somewhere in a ROM chip. The computer needs startup instructions to perform basic hardware checking and preparation, and these are contained in a ROM chip on the motherboard called the BIOS. This is where any computer begins executing its code when it is turned on.

I can't see any date on this, but this is a bit antiquated. For security and reliability, modern CPUs have an on-chip ROM, which is executed first. That on-chip ROM will tend do basic things like check clock, power, memory etc. Once that's complete it will then securely load firmware from the motherboard flash. Even modern cheapo microcontrollers are shipping with on-chip ROM these days.