P7

Polling

Polling is when the CPU checks the printer to see if it's ready to receive another it does this by using  ‘busy flag’ if the busy flag is on then the printer is not ready to receive another print. Polling is a good way of not overloading the printer. When the busy flag is off the computer will send the data to the printer the busy flag will represent the digit 1 to the CPU this makes the computer aware that the printer is not ready to receive data however when the busy flag represents the 0 it will make the CPU aware that its ready to receive data and is not busy yet. However the downside of using this system is that the CPU is constantly checking to see if the printer is ready and the printer is generating this flag it wastes a lot of resources trying to find this information out.

However the polling is treated as main priority with in the CPU this means this is the first task that the CPU will attempt if the printer is in use by another computer and the CPU is still checking if the printer is in use this may use a lot of valuable resources and slow down the computer.

P8

Comparison between RISC and CISC

CISC	RISC
Emphasis on hardware	Emphasis on software
Includes multi-clock complex instructions	Single-clock, reduced instruction only
Memory-to-memory: "LOAD" and "STORE" incorporated in Instructions	Register to register: "LOAD" and "STORE" are independent instructions
Small code sizes, high cycles per second	Low cycles per second, large code Sizes
Transistors used for storing complex Instructions	Spends more transistors on memory registers

The RISC machine executes instructions faster because it does not have to go through a microcode conversion layer. The RISC compiler generates more instructions than the CISC compiler for the same processing.

CISC:

Pronounced sisk, and stands for complex instruction set computer. Most personal computers use a CISC architecture, in which the CPU supports as many as two hundred instructions. The traditional architecture of a computer which uses microcode to execute instructions. Instructions may be variable in length and use all addressing modes, requiring complex circuitry to decode them.

RISC:

It’s a type of microprocessor that recognizes a relative limited number of instructions. One advantage is that they can execute their instructions very fast because the instructions are so simple. Another important advantage is that the RISC chips requires transistors which makes them cheaper to design and produce.

Advantages CISC	Disadvantages CISC
Microprogramming is as easy as assembly language to implement, and much less expensive than hardwiring a control unit.	Earlier generations of a processor family generally were contained as a subset in every new version so instruction set & chip hardware become more complex with each generation of computers.
The ease of microcoding new instructions allowed designers to make CISC machines upwardly compatible: a new computer could run the same programs as earlier computers because the new computer would contain a superset of the instructions of the earlier computers.	So that as many instructions as possible could be stored in memory with the least possible wasted space, individual instructions could be of almost any length---this means that different instructions will take different amounts of clock time to execute, slowing down the overall performance of the machine.
As each instruction became more capable, fewer instructions could be used to implement a given task. This made more efficient use of the relatively slow main memory.	Many specialized instructions aren't used frequently enough to justify their existence approximately 20% of the available instructions are used in a typical program.
Because microprogram instruction sets can be written to match the constructs of high-level languages, the compiler does not have to be as complicated.	CISC instructions typically set the condition codes as a side effect of the instruction. Not only does setting the condition codes take time, but programmers have to remember to examine the condition code bits before a subsequent

Advantages RISC	Disadvantages RISC
Speed. Since a simplified instruction set allows for a pipelined, superscalar design RISC processors often achieve 2 to 4 times the performance of CISC processors using comparable semiconductor technology and the same clock rates.
Simpler hardware. Because the instruction set of a RISC processor is so simple, it uses up much less chip space; extra functions, such as memory management units or floating point arithmetic units, can also be placed on the same chip. Smaller chips allow a semconductor manufacturer to place more parts on a single silicon wafer, which can lower the per-chip cost dramatically.
Shorter design cycle. Since RISC processors are simpler than corresponding CISC processors, they can be designed more quickly, and can take advantage of other technological developments sooner than corresponding CISC designs, leading to greater leaps in performance between generations.

P9

1)Fetch:

The Fetch Operation is used for taking the instructions those are given by the user and the Instructions those are stored into the Main Memory will be fetch by using Registers.

2)Decode:

The Decode Operation is used for interpreting the Instructions means the Instructions are decoded means the CPU will find out which Operation is to be performed on the Instructions.

3)Execute:

The Execute Operation is performed by the CPU. And Results those are produced by the CPU are then Stored into the Memory and after that they are displayed on the user Screen.