> BIOS is not stored in CMOS. It is in an EEPROM (or similar) these days. Flash usually > hardware features and test them." And so forth. Some tests require minor > amounts of ram. So setting up the path to the RAM is probably first. Then > a small bit, hundreds of bytes, is checked and used. Then, for example, > the onboard serial ports, parallel ports, and such can be initialized to > safe states and some quick checks performed on them. There is a ton happens even before the CPU begins operation - all the different voltage planes have to be powered up in the right order with the right timings. After that the processor begins execution and usually starts by running simple identification checks followed by manufacturer supplied initialisation sequences for the processor, for the cache (which is usually used instead of ram initially), then for the chipset logic, and after bringing the chipset up you can precharge all the RAM, test it and begin to use the hardware more like a real PC.
