Architectures

Question 1

What is CISC RISC debate

Answer 1

Debate considering how to split relative complexities and size of hardware and software

Question 2

CISC

Answer 2

Complex instruction set. A large instruction set to accomplish tasks in as few lines of assembly language as possible.
Complex processor hardware needs to be designed as it can understand and execute the series of subtasks that make up a single complex instruction.
Chipmakers provide a rich set of high level instructions to code with.

Question 3

How to distinguish CISC

Answer 3

Combining load/store with calculation

Question 4

Registers in CISC

Answer 4

Less registers to make space for complex decoder so data has to move about more in memory

Question 5

Cycles in CISC and RISC

Answer 5

CISC- a single instruction may take more than one cycle

RISC- a single instruction takes one clock cycle

Question 6

Memory movement for CISC

Answer 6

More movement in and out of CPU because fewer registers so often a bottleneck

Question 7

Coding and compiling CISC

Answer 7

Code is small, tight and easy to write. Compiler generates a single complex machine code instruction to achieve task

Question 8

RISC reduced instruction set computers

Answer 8

A relatively simple CPU decoder with more registers at the expense of having to write more lines of code to do the same thing

Question 9

RISC allows…

Answer 9

Parallel processing so performance improves e.g. LDA A and LDA B are independent

Question 10

Who provide RISC

Answer 10

ARM

Question 11

Who provide CISC

Answer 11

AMD and INTEL

Question 12

CISC is better for and RISC is better for…

Answer 12

CISC: complex maths
RISC: basic calculations and comparing (faster for this)

Question 13

CISC v RISC

Answer 13

• CISC more complex hardware
• CISC more addressing modes
• CISC has more compact software code v more complicated software code
• CISC has more instructions v limited instructions available
• CISC has variable sized bytes, RISC has a fixed number
• CISC uses less ram to store a program v more ram
• CISC fewer registers so more RAM used for intermediate results v more registers so less RAM movement
• Each instruction takes multiple cycles v each instruction takes one cycle each
• RISC = pipelining is possible
• RISC = more addressing modes

Question 14

Why programs run faster for RISC

Answer 14

Because simpler instructions, each taking one clock cycle

Question 15

Define co-processor

Answer 15

An extra processor used to supplement the functions of a primary processor , generally carrying out a limited range of functions. Not a general purpose processor able to fetch its own instructions

Question 16

Computers first built

Answer 16

1940s and 50s

Question 17

Pioneers of computers

Answer 17

Turing and Von Neumann

Question 18

Von Neumann machine key idea

Answer 18

Not only program but data being processed by program should be stored in the same memory. Data and instructions should share the same memory and buses
Stored program concept:
Machine code instructions are fetched decoded and executed serially, one at a time by a processor that performs logical and arithmetic operations. The program must be resident in main memory to be executed

Same data (and address) bus for (address of) instructions and data
Same word length for all memory: instructions and data

Question 19

Harvard key idea

Answer 19

Memory split into two parts which are physically separate, one for data and one for memory

Question 20

Why is Harvard better than Von Neumann

Answer 20

Faster as data and instructions fetched in parallel rather than competing for same bus

Question 21

The two memories in Harvard

Answer 21

Are physically separate and can have different characteristics e.g. Data in read write and instructions in read only for embedded
E.g. Instructions have more memory with wider bus and word size

Question 22

Harvard used extensively with

Answer 22

Digital signal processing: embedded e.g. Audio and image processing, sonar processing, radar processing, biomedical processing

Question 23

disadv of coprocessors

Answer 23

take up motherboard space, more expensive, uses a lot of power, limited by applications ability to take adv

Question 24

GPU

Answer 24

a co-processor used for offloading computer intensive parts of an application. It has a massively parallel architecture consisting of smaller, more efficient cores to handle tasks simultaneously (vs optimised for sequential serial processing.) Suitable for processing large blocks of visual data simultaneously and manipulating computer graphics and image processing.