Computer Architecture Essay Sample
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- Category: computer
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Computer Architecture Essay Sample
Describe how analogue data can be converted and stored in computer systems
Analogue data needs to be sampled in order to be processed by a computer. As computers deal in One’s and Zero’s it can only record specific intervals. For example, when recording a sound that gradually gets louder over a minute, a digital recording could record the level of sound every second, but would lose the information between seconds. If the sound was sampled every half second, there would be half as much information lost from the original source, but file size would be doubled. This is the trade off that has to be made between file size and quality.
Bit depth is the number of bits of information recorded per second .The higher the bit depth means, the higher the sample rate and this results in higher quality sound file. A good example of bit depth is in CD quality audio which has a bit depth of 16 bits and a sample rate of 44.1 kHz.
Task 3 (P5)
Describe the key components of a computer architecture and how they interact
1. Data Buffer – this is a region of memory used to temporarily hold data while it is being moved from one place to another.
2. Accumulator A – An 8 bit CPU has 1 register called the accumulator, this holds temporary data e.g. the carry-out when you do addition.
3. Arithmetic Logic Unit (ALU) – this is the workhorse of the CPU because it carries out all the calculations.
4. Data Buses – the mechanism that moves information around a computer.
5. Address Buffer – this holds the address part of the instruction register,
6. Program Counter – this contains the location of the next instruction to be executed and, therefore, keeps track of where the computer is up to in a program.
7. Instruction Register (IR) – this divides the information it receives into two fields. One field in the IR contains the operation code that tells the CPU what operation is to be carried out. The other field, called the operand field, contains the address of the data to be used by the instruction.
8. Condition Code Register (CCR) – this takes a snapshot of the state of the ALU after each instruction has been executed and records the state of the carry, negative, zero, and overflow flag-bits. In the above diagram the flag-bits are H, I, N, Z, V & C.
Task 4 (P6)
Describe the features of a processor
Multi-tasking is a method where multiple processes are dealt with at once sharing common processing recourses such as a CPU. It involves the CPU assigning which instructions to be carried out first but it only focuses on one instruction at a time.
Pipelining is a method in which the Processor begins to execute a second instruction before the first has finished. Every pipeline is divided into segments and each segment can be ran along side each other. When each segment completes its task it moves on to the next.
Cache (Level 1 and Level 2)
Cache is a portion of memory made of high-speed static RAM (SRAM). As a result Cache memory is much more efficient than the main memory (RAM) which is dynamic RAM (DRAM) that runs slower but also cheaper. The cache is a smaller, faster memory which stores copies of the data from the most frequently used main memory locations.
DRAM is dynamic in that, unlike SRAM, it needs to have its storage cells refreshed or given a new electronic charge every few milliseconds. SRAM does not need refreshing because it operates on the principle of moving current that is switched in one of two directions rather than a storage cell that holds a charge in place.
If the computer processor can find the data it needs for its next operation in cache memory, it will save time compared to having to get it from random access memory.
Level 1 cache is normally built on to the processor chip. It is extensively used for all sorts of purposes such as data fetching, data shifting and data loops, storing only small amounts of data.
Level 2 cache is normally located on the motherboard. L2 cache stores much more data, coming usually from the L1 cache. L2 cache can be up to sixteen times the size of L1 cache; this also means that it takes up much more room so it has to be located on the motherboard.
The clock rate is the speed at which a processor clock oscillates constantly from a one to a zero, this is measured in hertz. The clock rates speed is determined by an oscillator crystal and amplifier circuit inside a clock generator circuit. The limiting factor of the clock rate is the time it takes for the signal line to settle down from its on state to off state. The Clock rate is also as fast as L2 cache.
Task 5 (P7)
Describe the operation of logic gates using truth tables
* AND (2 inputs)
* OR (2 inputs)
Consider how these three main gates can be combined
* NOR (2 inputs)
NOT Logic Gate also known as (Inverter)
The output is “true” when only one input is “false.” Otherwise, the output is “false”. A Not gate is a logic gate which reverses the state of the input.
AND Logic Gate
The output is “true” when both inputs are “true.” Otherwise, the output is “false.”
OR Logic Gate
The output is “true” if either one or both of the inputs are “true.” If both inputs are “false,” then the output is “false.”
These three main logic gates can be used to make other possible combinations of logic gates such as a NOR gate.
NOR Logic Gate
The NOR gate is a combination of an OR gate followed by an inverter. The output is “true” if both inputs are “false.” Otherwise, the output is “false.”
Task 6 (M1) Explain using examples how data travels around the processor
Task 7 (M2) Create logic circuits using simple logic gates and provide truth tables
This is a circuit that shows binary addition.
Here are a few examples of the circuit being carried out.
The Red circle/circles show input and Green circle/circles show output data
This can be shown in the truth tables below.
Task 8 (M4)
Provide a description of both astable and bistable flip- flops.
A flip-flop is an electrical circuit that can be in one of two states.
Astable flip flop
Astable flip flop is an oscillator which regularly switches states all the time. It has one 1 input and 1 Output. It can be used as a clock.
Bistable flip flop
Bistable flip flop is a memory device/gate which keeps one state indefinitely while it has power it also has 2 inputs and 2 outputs.
The difference between An Astable and Bistable flip flops.
A bistable flip-flop is a multivibrator with two stable states and can be put into either of its two states and it will stay like that.
An example of this could be:
A simple light switch; turn it on, it stays on, turn it off, it stays off.
Task 9 (D1)
Create complex logic circuits made up of arrays of simple logic circuits.
To produce an addition of two numbers each of four bit’s in length we must first.
You can add two numbers together each four bit in length by extending the first full adder’s carry out to another full adder and so on. Until you get 4 full adder’s each following on from the last carry out.
The way a full adder works:
The circuit adds two bits Input A and Input B, taking into account the previous carry in, to give the Sum, and the carry out.
Now we know how a full adder works we can now relate this to the idea of 4 full adders joined together by the last carry out and the diagram below illustrates this.