Computer Hardware: What is Motherboard, Bios, CMOS, CPU, RAM, etc.

A computer is the sum of it’s parts. One part alone doesn’t make a computer. Typically the primary hardware components that make up a computer is the CPU (Central Processing Unit), Memory (main memory), Storage Devices (like flash drives, cds, HDD), Input Devices (keyboard & mouse), Output Devices (i.e. Monitors and Printers), and Communication devices (i.e. modems and network interface cards).

A computer parts are interconnected by the bus. A bus is a system or roads that run from one component to another, allowing data & power able to reach all the components. For personal computers, the bus is built into the Motherboard.


A motherboard is  a circuit case that connects all the parts of a computer together. Motherboards can be monolithic or modular. Monolithic refers to motherboards that don’t give you the option of customizing internal parts (like Macs). Modular refers to motherboards that allow you to customize and swap parts (Dell).


BIOS stands for Basic Input Output System. Bios is the software embedded in a chip on the motherboard. This Software is responsible for checking the memory, processor, and other components are functioning properly before the PC boots up. Error Checking done by Bios is called POST (Power On Self Test). POST is recognized as beeps. BIOS also tells the computer how to turn on.


Stores setting data from the BIOS -or- Can mean the same as BIOS. Resets when CMOS battery is removed.


The CPU stands for the Central Processing Unit. The CPU is the computer’s brain, so to speak. It retrieves instructions from the memory and executes them.

The CPU usually has two components: a control unit and an arithmetic/logic unit. The control unit controls and coordinates the actions of the other components. The arithmetic/logic unit performs numeric operations (addition, subtraction, multiplication, division) and logical operations.

Today’s CPUs are built on small silicon semiconductor chips that contain millions of tiny electric switches, called transistors, for processing information.

Every computer has an internal clock, which emits electronic pulses at a constant rate. These pulses are used to control and synchronize the CPU’s pace of operations. A higher clock speed enables more instructions to be executed in a given period of time. The unit of measurement of clock speed is the hertz (Hz), with 1 hertz equaling 1 pulse per second.

Most modern CPUs are microprocessors, meaning they are contained on a single integrated circuit (IC) chip. An IC that contains a CPU may also contain memory, peripheral interfaces, and other components of a computer; such integrated devices are variously called microcontrollers or systems on a chip (SoC). Some computers employ a multi-core processor, which is a single chip containing two or more CPUs called “cores”; in that context, single chips are sometimes referred to as “sockets”. Array processors or vector processors have multiple processors that operate in parallel, with no unit considered central.

CPU prioritizes data retrieval like so: L1 > L2 > L3 > RAM > Hard drive

Computer Storage & Memory

In computing, memory refers to the computer hardware devices used to store information for immediate use in a computer; it is synonymous with the term “primary storage”. Computer memory operates at a high speed, for example random-access memory (RAM), as a distinction from storage that provides slow-to-access program (HD drive) and data storage but offers higher capacities. If needed, contents of the computer memory can be transferred to secondary storage, through a memory management technique called “virtual memory”.

Most semiconductor memory is organized into memory cells or bistable flip-flops, each storing one bit (0 or 1). Flash memory organization includes both one bit per memory cell and multiple bits per cell (called MLC, Multiple Level Cell). The memory cells are grouped into words of fixed word length, for example 1, 2, 4, 8, 16, 32, 64 or 128 bit. Each word can be accessed by a binary address of N bit, making it possible to store 2 raised by N words in the memory. This implies that processor registers normally are not considered as memory, since they only store one word and do not include an addressing mechanism.

Memory is often associated with addressable semiconductor memory, i.e. integrated circuits consisting of silicon-based transistors, used for example as primary storage but also other purposes in computers and other digital electronic devices. There are two main types of semiconductor memory, volatile and non-volatile. Examples of non-volatile memory are flash memory (used as secondary memory) and ROM, PROM, EPROM and EEPROM memory (used for storing firmware such as BIOS). Examples of volatile memory are primary storage (typically dynamic RAM, DRAM), and fast CPU cache memory (typically static RAM, SRAM, which is fast but energy-consuming and offer lower memory capacity per area unit than DRAM).

Cache Memory

Note that Cache memory is the fastest memory, and is closely situated to the CPU for efficiency (less time taken for signal to reach CPU).


RAM, or Random Access Memory, is a form of computer data storage that allows for changes to stored data (in contrast to ROM). In other words, RAM is re-writable, and ROM is not. RAM is a type of volatile memory, meaning the data stored is lost if the power is removed.


Hard Disk Drive (HDD) is a computer data storage device. It contrasts from RAM & other memory by storing data for long periods of time without loss, and not losing data when the power is removed. HDD uses rapidly rotating disks that are coated with magnetic material. This magnetic material store changes applied to it by the magnetic heads; this is how data is “etched” onto the Hard Disk Drive.

HDD Internal



ROM, or Read-Only Memory, is a type of non-volatile memory. Read-Only means that you cannot make changes to the stored data on the memory. Non-volatile means that the data on the memory is not erased when the computer is turned off. Typically, ROM is used to store instructions that are required to start a computer. These instructions are called bootstrap.

Router & Switch

Network Router is a networking device that delivers data packets between computers on a network. Routers can connect multiple networks together for computers to communicate through.

Network Switch is just like a router, except the Switch only connects data lines from one single Network. Router connects multiple networks. …

Takeaway: Router can connect multiple networks, Switch only connects a single network.

Switch vs Router
A Switch functions by moving/forwarding data frames based on MAC address. This happens at that lower level of the network in what is known as Layer 2 (Data link layer) of the OSI Model.  When communications happen it is from MAC address to MAC Address, or hardware to hardware

A Router functions by moving/routing data packets based on IP address.  This happens a little higher in the network in what is known as Layer 3 (Network layer) of the OSI Model. When communications happen here it is from IP address to IP address.

Network Card is an electronic device that connects a computer to a Network.

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