(7) Computer Architecture Flashcards

Question

What happens in the Fetch-Decode-Execute cycle? (Mentioning registers)

Answer 1

Fetch: Contents of Program Counter (PC) is transferred to Memory Address Register (MAR); Address bus are used to transfer this address to main memory; Contents of addressed memory location is loaded into the Memory Buffer Register (MBR); Transfer of content uses the data bus; Increment contents of Program Counter (PC) by 1; Increment Program Counter / PC and fetch simultaneously; A any part of fetch process Transfer content of Memory Buffer Register (MBR) to the Current Instruction Register (CIR) Decode: Decode instruction held by the Current Instruction Register (CIR); The control unit decodes the instruction; Instruction split into opcode and operand; Execute: The opcode identifies the type of instruction it is; Execute instruction by relevant part of processor; Result stored in accumulator; Status register updated; If jump / branch instruction Program Counter/PC is updated;

Answer 2

- No. of cores - The amount and type of cache - Clock speed - Word length - Address bus width - Data bus width

Answer 3

Number of bits which can be addressed at a time

Answer 4

A secondary storage device - Made up of disks arranged in a stack - Binary digits are represented by magnetise spots on a disk - Disks are divided into tracks and sectors - The disk continuously spins - A drive head can move in and out to read and write data

Answer 5

- Uses laser technology to read and write data - Made up of a spiral track that starts from the centre outwards - Within the track there's pits and lands which represent 1s and 0s - The track is read by the laser and interprets each reflection from the laser

Answer 6

Fast memory

Answer 7

- Consists of a light source, lens and photoelectric detectors - The scanner shines a light on the black and white bands (lines) - The white is reflected more than the black (i.e. can distinguish between them) - The pattern is turned into electrical data and is analysed by a computer - The electrical signal is usually decoded into a number

Answer 8

* Shutter opens and lets light through the lens * The light is focussed onto a sensor * Sensors are made up of millions of transistors which stores the data for one or more pixels * As the light hits the sensor it is converted into electrons and the amount of charge is recorded for each pixel in digital form * Mark scheme: Camera/CCD measures (ambient) light reflected from bar code; • Camera/CCD converts light into an electrical signal; • Light reflected back; • Black areas reflect less light than white; • Raw image data transmitted to computer; • Image analysis software analyses image to determine value encoded in • bar code;

Answer 9

- The printer generates a bitmapped image - Laser turns on and off and is directed at the drum - The drum rotes - The drum is coated in a negative charge which the laser neutralises - As the drum rotates the image is drawn into the drum - The toner is picked up and transferred to the paper - Heat and pressure fuse the toner to the paper Exam Mark scheme: Page printer; Print drum coated in (negative static) charge; Printer generates bit map of page; Laser beams shone/directed at/"draws" on print drum; Via rotating (octagonal) mirror; Laser is modulated (turned on & off); Laser removes/neutralises/reverses electric charge on drum; where image should be dark/black: Toner is given (negative) charge; Charged drum picks up toner; Toner transferred from drum to paper; ("from drum" may be implicit in order of answer) Toner is fused/bonded/melted/stuck to paper by (heated rollers/pressure; (must be clear that toner is already on paper when it is fused, not still on drum)

Answer 10

increase the number of bits that can be transferred at one time... increasing the speed

Answer 11

increases the number of memory addresses

Answer 12

The amount of available memory locations will double

Answer 13

- instructions performed more quickly - instructions executed at faster rate - fetch execute cycle will happen faster - increased heat may cause malfunctioning of device - overheating

Answer 14

The idea that instructions and data are stored together in memory - instructions are stored in main memory; - instructions are fetched, (decoded) and executed by the processor; - programs can be moved in and out of main memory

Answer 15

Data bus has to transport data values to and from various internal components ; Only the processor assigns address values to the different components;

Answer 16

- Instruction(s); - address(es);

Answer 17

Address only goes from the processor to main memory

Answer 18

Direct addressing means that the operand is the memory address Tells the CPU which address contains the data you want to access Whereas, Immediate addressing means the operand is the data. It loads the data directly

Answer 19

Opcode- Indicates the instruction part i.e. add Operand- Represents a set of binary data

Answer 20

The complete set of all the instructions in machine code that can be recognised and executed by a CPU

Answer 21

Fetch MAR ——[PC] PC ——[PC] + 1 MBR —— Memory Contents CIR ——[MBR] Decode Instruction Execute Instruction

Answer 22

We need it because it retains its contents when the power is turned off unlike ram