What is a computer?

Computer Interface

4 Layers

• Layer 4: Applications (OS)​

• Layer 3: Kernel​

• Layer 2: Hardware Abstraction Layer​ (HAL)​

• Layer 1: CPU Memory MMU, Timers and Ports/Devices​

Level 4: OS 1

• An Operating System (OS) is considered the most important software that runs on an computer. ​

• It allows users to operate and communicate with the hardware on the computer.​

• Ergo a Computer useless without the OS.​

• OS manages all the Software and Hardware on the computer

Operating Systems

Types of OS generally come in three flavours:​

1. Microsoft Windows (Win 11, Win10, XP, VISTA, 3.0)​

2. MacOS (Cheetah, Puma, Big Sur)​

3. Linux (distros-> Ubuntu, Redhat, Kali)​

4. Dos​

Level 3: Kernel

Kernel...

• The kernel is a busy personal assistant for a powerful executive (the hardware). ​

• It’s the assistant’s job to relay messages and requests (processes) from employees and the public (users) to the executive. ​

• To remember what is stored where (memory).​

• To determine who has access to the executive at any given time and for how long.​

Kernel...

If implemented properly the Kernel is invisible to the user, working in its own little world known as the Kernel Space. Like where it allocates memory and track of where everything is stored. The User Space is the files or applications, what the user sees!​

​

The Kernel is software​

Level 2: Hardware Abstraction Layer (HAL)

The HAL handles the communication between the Kernel of the OS and the Hardware​

Level 1: Hardware

Basic components of modern digital computer are:​

• Input/Output device (I/O)​

• Central Processing Unit (CPU)​

• Mass Storage Device​

• Memory

Functions of a Computer​

So therefore the four main functions of a computer are:​​

1. Input

2. Processing

3. Output

4. Storage

What parts are needed for a computer work?

Processor​

• Component that executes instructions from the software and hardware​

Memory​

• Temporary primary storage for data travelling between storage and CPU​

Motherboard​

• Component that connects all components.​

Storage Device​

• Slower Secondary storage that permanently stores data.

But wait, there are other types of computers

Back to the Architecture

Now we are going to have a look at the CPU and in part the memory and how they are related.​

Central Processing Unit

• Chipset dictates what type of CPU you have​

• Likewise because the CPU has the memory controller built-in this dictates what Chipset you have.

• DMI (Direct Media Interface ) a high speed BUS (data highway , ‘omnibus’ [Latin])​

• Chips controls the flow of data and instructions to the CPU​

Cores

• CPU have multiple cores​

• Own CU, ALU and registers​

• Independently processing programming instruction​

• Software can take advantage of this and therefore double number of cores double rate of execution.​

Cache Levels

Crystal Oscillator - Base Clock

• 100 million times a second – cycle is 10ns​

• Base clock, tempo, is multiplied by a frequency multiplier to increase the rate of instructions executed​

• Multiplying by 35 we get 3.5Ghz, which 0.3ns per cycle​

​

Overclocking

Overclocking, suppling more voltage to the crystal to increase the frequency.​

Means faster system, calculations, instructions etc. ​

More power more heat

Example CPU

Core speed is the multiplication result, per core

Multiplier CPU dynamically adjust clock speed​

Bus Speed Base clock frequency from the Quartz crystal​

Example Cache

L1 Cache is​ In two parts, Instruction and ​Data. Both are 32 KBytes in size​

L2 Cache as expected is larger at 256 Bytes​

L3 Cache Finally, L3 is 6M bytes

Example Memory

DRAM:Frequency Speed of the memory bus​

FSB:DRAM Base clock /3 * up to get DRAM Frequency ​

Column Address Strobe (CAS) latency, or CL, is the delay in clock cycles between the READ command and the moment data is available. Smaller the number the better​