What Is Inside That Beige Box

What Is Inside That Beige Box?

Power Supply
The +3.3V and +5V circuits supply power to all the electronic circuitry in the system (motherboard, adapter cards and disk drive logic boards), and through the port sockets on the motherboard that poke out through the rear of the case, to the peripherals that don't have their own power supply (e.g. keyboard, mouse).
Power supplies are often overlooked, but are essential to the proper operation of your system which requires a good, steady supply of DC power at the appropriate voltages. These voltages must be constant, right up to the maximum current your system will draw under load.

CPU
The CPU (Central Processing Unit) is the brain of the system. It executes all the program code from the operating system and the applications you run, and does most of the calculating and processing of data. It sends commands to direct the actions of all the other components in the PC and it manages the distribution of data to/from those various components.

Inside the CPU are registers, arithmetic and logic units (ALU), a floating-point unit (FPU), control circuitry and cache memory. Registers are circuits designed to hold data so that it can be processed in some way by an ALU or the FPU. Cache memory is extremely fast, but small relative to the main memory. Cache memory is used to store the current set of working data and code. So when the processor needs to read the next bit of data or code, usually it can retrieve it much faster from the cache. On occasions when it must recall data from the (slower) main memory, the CPU is forced to wait instead of getting on with other operations.

The CPU is the fastest component in your system. It works hard only sometimes, maybe when you play a game involving 3D graphics, or perhaps compile a very large program or run a very large spread-sheet; but most of the time it is just waiting for you to press the next key, or for the next bit of data to arrive from the Internet, through your modem.

Main Memory or RAM (Random Access Memory)
Memory is temporary storage where the processor can access program code and data. It is temporary because any information stored there is lost when the system loses power or is rebooted.

A low or high (on or off) voltage state in those small circuits represents a "0" or "1", which are the only two possible states of a binary digit (a "bit").