Computer Architecture Multiple Choice Test PDF

# Von Neumann and Harvard Architectures ## Von Neumann-Definition - Memory holds both data and program. - Data and programs are stored together. - It is a diagram showing the CPU memory, control unit, arithemtic logic unit, and accumulator. - Two boxes representing **data** and **program**...

# Von Neumann and Harvard Architectures ## Von Neumann-Definition - Memory holds both data and program. - Data and programs are stored together. - It is a diagram showing the CPU memory, control unit, arithemtic logic unit, and accumulator. - Two boxes representing **data** and **program** are shown inside the memory unit. - Arrows between the boxes show how the control unit and the ALU interact with the memory unit. - **Question:** How do we know what we get inside the CPU - Program or Data? - **Rule:** We assume the first piece of information is always a command, followed by possibly data. ## Harvard-Definition - Programs (commands) and data are stored separately. - It is a diagram of the CPU showing the ALU, instruction memory, control unit, data memory and the 1/0 unit. - Two boxes, **instruction memory** and **data memory**, represent separate memory units for programs and data. - **Question:** How do we know what we get inside the CPU - Program or Data? - **Rule:** We know that information from instruction memory is a command and information from data memory is data. ## The Motherboard - The motherboard is the backbone of the computer. - It is a printed circuit board (PCB) that contains buses and electrical pathways. - These components may be soldered directly to the motherboard or added using sockets, expansion slots, and ports. ## The Modern Motherboard - It is a photo of a modern motherboard. - The image shows several components, labels, and connectors. - **BIOS:** Boot program to power up the motherboard and configure the chipset devices. ## Which one CISC or RISC CPU's? - **RISC (Reduced Instruction Set Computer)** and **CISC (Complex Instruction Set Computer)** - Both are popular processor architectures that use different data processing instruction sets. - **CISC:** - Reduced code size. - More efficient memory use. - Popular. - **RISC:** - Simpler instructions. - Faster execution. - Lower power consumption. - **CISC:** - Slower execution. - More complex design. - Higher power consumption. - **RISC:** - More instructions needed. - Increased memory usage. - Higher cost. ## The System Bus Model - Although the von Neumann model prevails in modern computers, it has been streamlined. - The below figure shows a diagram of the system bus model of a computer system. - This model partitions the computer system into three subunits: - CPU - Memory - Input/Output (I/O) - This refinement of the von Neumann model combines the ALU and the control unit into one functional unit, the CPU. - The input and output units are also combined into a single I/O unit. - The System Bus consists of three buses: - Data bus - Address bus - Control bus ## The Fetch and Execute Cycle - The life and times of a CPU is that of a gopher. - It is a simple program that is often stored as a series of numbers in memory - **Load num1 (30)(10):** CPU reads 30 which is the command Load from the memory via the Bus (read cycle). - **Load num2 (30)(20):** CPU read command 10 which is num1 address from the memory via the Bus ( read cycle). - **Add num1+num2 (40):** Now has whole command (fetch cycle complete (30, 10) -> Load num1. CPU now does the command "execute cycle"- the number is read from location 10 and stored in the CPU. - **Store answer in num3 (40)(40):** CPU reads 30 which is the command Load from the memory via the Bus (read cycle). ## The CPU Components - The Central Processing Unit (CPU) has two major components: - Control unit. - Arithmetic-Logic Unit (ALU). - It also has a number of special registers that carry out these operations. - A register is a very fast memory location. ## The CPU Components + Registers - A diagram of the central processing unit, the arithmetic-logic unit, and registers. - Registers include: - PC - CIR - AC - MAR - MDR ## The CPU Components - "The control unit co-ordinates and controls all the operations carried out by the computer." - The control unit: - Controls and monitors hardware attached to the system. - Controls input and output of data. - Controls the flow of data within the CPU. ## The CPU Components - **Arithmetic Logic Unit (ALU):** Performs two sorts of operations on data: - **Arithmetic operations:** Addition, subtraction, multiplication, division. - **Logical operations:** Comparing one data item to another: is it smaller than, greater than, or equal to? ## The CPU Components - Registers - **Program Counter:** Holds the address of the next instruction to be executed. - It is located in the Control Unit. - It gets incremented as soon as that instruction has been fetched. ## The CPU Components - Registers - It is a diagram showing the CPU, control unit, arithmetic logic unit, accumulator, MDR, PC, CIR and MAR. - **Program Counter (PC):** Points to the next instruction to be executed. - **Current Instruction Register (CIR):** Holds the current instruction to be executed. - **Memory Address Register (MAR):** Stores the memory address of the current instruction and the data it uses and is used to fetch them from memory. - **Memory Data Register (MDR):** Stores the actual instruction or data that has been fetched from memory. - **ALU:** Temporarily stores arithmetic and logic results and holds the result before the results are transferred to memory. ## The CPU Components - A bus is a set of parallel wires connecting two or more independent components. - It is used to pass signals between them. - The bus is divided into three separate buses: - Data bus - Address bus - Control bus ## The CPU Connections - The electrical wires coming from the CPU can be grouped into three groups: - Address bus: 16, 32, 64, 128 bit - Data bus: 8, 16, 32, 64 bit - Control bus: read/write, clock,DMA, interrupts etc. ## The CPU - **Question:** How does a CPU work? - The standard CPU operates using a FETCH/EXECUTE cycle. - CPU spends most of its time reading the program, understanding the command, and then doing the command. - The Program/data is stored in external memory in binary/hex and is transferred into the CPU via the bus. ## Interface Standards - ISA - Industry Standard Architecture (ISA) - The development of the IBM XT/AT came with the first industry-wide interface standard. - It was an extension of the FSB (Front Side Bus). - It used the address and data bus in the form of a common connector. ## Interface Standards - PATA - The next major connector is the hard disk/DVD-ROM connection. - It is a 80-wire cable. - The connector allows connection of more than one device using a jumper. - The maximum speed a PATA (IDE) unit can achieve is 133MHz with 16 bits. - **PATA:** Parallel Advanced Technology Attachment. ## Interface Standards - SATA - Current ATA is the **Serial ATA**. - The serial version replaced the parallel cable with a differential serial cable. - This enables the operating system to support different data widths, i.e. burst mode. - It improves the transfer speed and variable transfer speeds. - The maximum speed of a SATA interface: - SATA V1: Bandwidth = 1.5 Gb/sec, Data Transfer = 150MB/sec. - SATA V2: Bandwidth = 3.0 Gb/sec, Data Transfer = 300MB/sec. - SATA V3: Bandwidth = 6.0 Gb/sec, Data Transfer = 600MB/sec. - **SATA:** Serial Advanced Technology Attachment. ## Interface standards- ISA - Industry Standard Architecture (ISA) - It is a table of the upper and lower signals in the ISA 8-bit. ## Interface standards - EISA - Extended Industry Standard Architecture (EISA) - A table showing the memory, I/O, IRQ, DACK and DRQ connections. ## Interface standards EISA - EISA Data Transfer is 16 bits 8.33 MHz Maximum speed. - It is NOT - Giga Hertz. ## Interface Standards - PCI - **Need for speed… PCI (Peripheral Component Interconnect)** - With the development of CPU's and speed improvements, the Extended Industry Standard Architecture (EISA) bus was slowing down the overall computer. - **Alt view:** Driving a sports car in first gear. - The computing industry created a closed shop standard called the 'Peripheral Component Interconnect - PCI' standard. - It introduced a new connector, motherboard, and chipsets. ## Interface Standards - PCI - **Difference between ISA and PCI:** PCI is a significantly faster bus than Extended Industry Standard Architecture (EISA). - It has a double (quadruple in rare instances) bit-width, resulting in faster data transfer. - **Why change?** Enables higher speeds: - V1 = 33MHz, V2 = 66 MHz, 8/16/32 bit data bus. - Full support from Windows 95 to Windows 11 with plug and play. - The software could automatically set up the hardware. ## Interface Standards - At the same time as CPU development is happening, graphics development also occurred. - Software/multimedia programmers moved from 2 bit black/white or 8 bit color CGA graphics. - The programmers started using 16/32 bit color with textures. - Moving large amounts of data down the FSB (Front Side Bus) through the PCI slot to the graphics card caused a problem for the FSB. ## Interface Standards AGP - Since the speed of the PCI was only 66MHz, it caused a problem. - This led to the introduction of a new standard called **Advanced Graphics Port (AGP)**. - The AGP was based on the existing PCI standard. - It enabled a speed increase from 66Mhz to 1GHz. ## Interface Standards-AGP - Developments in graphics cards are never static. - They are constantly changing between processing the rendering locally within the card or the main CPU. - Some cards have dedicated graphics processors and 1TB of memory. ## Interface Standards PCIe - Recently motherboard manufacturers have virtually phased out most of the standards. - They introduced an overall new connection called 'Pica express.' ## Interface standards PCle - The PCle specification is fairly new. - It changed the standard to a serial protocol (x1). - It allows multiple serial channels to work at the same time. - This was possible to achieve x4 x8 x16. ## Variations of Drives? - **Solid state Hard drive (SSHD):** Best of both worlds, magnetic drive and solid state drive. - **Not SSD:** SSD drive is a solid state drive with no moving parts. - **Question:** Which one is better, SSHD or SSD? - **SSHD:** - **Lifetime:** less block copy. - **Cost:** More cost effective than SSD. - **Data Capacity:** Larger capacity than SSD. - **Access Time:** Faster access time than HDD but slower than SSD. - **SSD:** - **Windows:** Better for Windows installation. - **Bulk Storage:** Better for bulk storage than SSHD. ## Choosing a Storage Drive? - When choosing a storage drive, the main factors are: - Data transfer time. - Rotational speed. - On board cache. - Form factor. - Interface standard. - Data storage size. - Cost. - Lifetime - SSD/SSHD. - **Questions:** How hot is it? Does it need water cooling? ## How are CPU's made? - CPU's are made with Silicon doped with group 3,5 materials. - The combination of adding together these semiconductors produces the **transistor (an electronic switch)**. - **Transistors** can be combined to create **more complex devices, such as logic gates**. - These logic gates are the foundation of digital circuits and computer systems. ## Basic Building Blocks - In computing, we associate **TRUE** with binary '1' and **FALSE** with binary '0'. - **Logic elements** are represented as truth tables of 0' and 1's. - **Truth table input** can be calculated by counting in binary, adding 1 each time. - 00 + 1 = 01 - 01 + 1 = 10 - 10 + 1 = 11 - **Logic gates** are fundamental building blocks of digital circuits. - **AND gate:** Output is TRUE only if both inputs are TRUE. - **OR gate:** Output is TRUE if at least one input is TRUE. - **NOT gate:** Output is the inverse of the input. ## | Blocks together to form More - Logic gates can be combined in various ways to create more complex logic functions. - **NAND gate:** A combination of an AND gate and a NOT gate. - **NOR gate:** A combination of an OR gate and a NOT gate. ## Exclusive OR - **XOR gate:** It is a diagram of an XOR gate with a truth table below. - The output is TRUE if only one input is TRUE. ## SSI, MSI, VLSI, LSI, Devices - **Basic building blocks** are joined together to create **more complex blocks**. - The complexity of the logic circuit is described based on the packing of the devices onto silicon. - **Small Scale Integration (SSI):** Devices with a few transistors on a single chip. - **Medium Scale Integration (MSI):** Devices with hundreds of transistors on a single chip. - **Large Scale Integration (LSI):** Devices with thousands of transistors on a single chip. - **Very Large Scale Integration (VLSI):** Devices with millions or billions of transistors on a single chip. ## Truth Tables - **Truth tables** are used to represent the logic functions of gates. - Shows the relationship between the input and output states of the gate. - It includes tables showing how AND, OR, NOT, NAND, NOR, and XOR gates work. ## Types of Memory - **ROM (Read Only Memory):** Data is permanently stored and cannot be modified. - **RAM (Random Access Memory):** Data is volatile, meaning it is lost when the power is turned off. - RAM includes: - **SRAM (Static RAM):** Uses latches to store data. - **DRAM (Dynamic RAM):** Uses capacitors to store data, and data needs to be refreshed periodically. - **EPROM (Erasable Programmable Read-Only Memory):** UV Light erasable ROM. - **E2PROM (Electrically Erasable Programmable Read-Only Memory):** Slow high voltage erasable ROM. - **FLASH ROM:** Low-voltage erasable ROM, provides a balance between the performance of SRAM and the affordability of DRAM. ## Memory Hierarchy - A pyramid diagram showing the memory hierarchy in a CPU. - The hierarchy is based on the speed and capacity of each memory type. - **On CPU:** - **Registers:** Fastest memory, but very small. - **Cache:** Small, but faster than main memory. - **Primary Storage:** - **Main Memory:** Larger than cache, but slower. - **Secondary Storage:** - **Flash Disk:** Relatively fast and large capacity. - **Traditional Disk:** Slower than flash disk, massive capacity. - **Remote Secondary Storage:** Slowest, but has massive capacity. ## Virtual Memory - A diagram showing the interaction between the CPU, MMU, memory, and disk controller. - The CPU sends virtual addresses (logical addresses) to the MMU (Memory Management Unit). - The MMU translates it into physical addresses and sends it to the memory for access. ## Virtual Memory - It is a diagram showing how virtual memory works. - The virtual memory space can be larger than the physical memory space. - It uses a page table to map virtual addresses to physical addresses. ## Virtual Memory - A diagram to visualize the workings of virtual memory. - The logical memory space (virtual) is mapped to the physical memory space (real). - The page table is used to translate virtual addresses to physical addresses. - **Fragmentation:** The fragmentation of memory (unused spaces) will affect performance. ## Memory - Design and Performance - **Factors influencing memory performance:** - **Access Time:** Speed at which data can be read from or written to memory. - **Data Bus Size:** Width of the data path, determining how much data can be transferred at once. - **Cost per Gigabyte:** The cost of memory per unit of storage. - **Cooling Requirements:** Heat produced by the memory. - **Availability:** How readily the memory module is available in the market. - **Compatibility with Motherboard:** Ensuring compatibility between the memory and the motherboard. ## RAMBUS - **RAMBUS** is a type of memory technology. - It is a diagram showing a RAMBUS chip. - **One major development** was the total redesign of DDR memory. - **Changes:** - A new protocol-based interface (RAM bus controller). - It changed the electronic voltage levels of logic '0' and logic '1' to improve speed. ## Memory - RAMBUS changed the electronic voltage levels of logic '0' and logic '1' (threshold levels) - It reduces the time for electronics to reach logic '1', leading to faster RAMBUS threshold levels. ## RAMBUS problems - If we reduce the logic threshold, then the logic levels are more prone to interference from noise. - This can cause data problems. - RAMBUS is installed in matched pairs to balance the bus system. - This is done to reduce the effect of electronic noise. ## Light and Color - By combining lights of different wavelengths, we can see **different colours**. - The colors are different from any of the constituent colored lights. - **In physics and light, the three primary colours are:** - Red - Green - Blue (RGB) - **Additive color mixing:** Combining light of different wavelengths is known as additive color mixing. It defines the RGB color model. - **White:** Produced by combining red, green, and blue in equal proportions. ## Pixels and Colour displays - Digital images consist of a large number of discrete small areas, each of which has a **specific colour.** - **Pixel (Picture Element):** A small area that comprises a digital image. - **RGB colour model:** Each pixel is composed of three small areas, one for each primary colour. - The colour of the pixel is determined by the degree to which each area glows. - **Dot pitch:** Distance between pixels. ## Display standards - Over the years, a number of display standards have evolved. - **The most important ones are:** - VGA (Video Graphics Adaptor) - SVGA (Super VGA) - XVGA (Extended Graphics Array) - WXGA (Wide Extended Graphics Array) - HDMI (High-Definition Multimedia Interface) - Ultra HDMI (4K/8K) - **Display standard:** Identifies a series of video display modes, which defines: - **Display resolution:** Number of pixels on the screen. - **Range of colours:** Total number of colours available to define a pixel color. ## Terminology - **Resolution:** Number of pixels on the screen (X and Y). - **X:** Number of horizontal pixels - **Y:** Number of vertical pixels - **Various standards exist:** - **VGA:** (Lowest standard) 640x480 - **SVGA:** 800x600, 1024x768 - **XVGA:** 1024x768 - **WXGA:** 1280x720 - **HDMI:** 1920×1200 - **8k HDMI:** 7680x4320 -**Dot pitch:** Distance between pixels - typically 0.26mm. ## Terminology (Continued) - **Refresh rate:** Frequency of repainting the screen. - **100Hz:** Repainting the screen 100 times per second. - **Dot frequency:** Number of pixels output to the screen per second. - It is calculated by multiplying the size of the display by the refresh rate. - **Aspect ratio:** Ratio of the width to the height (4:3 or 16:9). - **Size of screen:** Diagonal of the display. ## Another Terminology: Colour Depth - **Colour depth:** Number of bits used to represent the range of colours in a display. - **8-bit:** Represents 28 = 256 different colours. - Part of the VGA standard. - **16-bit:** Represents 216 = 65,536 different colours. - Known as "High Colour" and is available in SVGA. - **24-bit:** Represents 224 = (approx.) 16 million different colours. - Known as "True Colour" – defined in the SVGA standard. - **30/36/48-bit:** Represents 248 = (approx.) 281.5 trillion colours. - Known as "Deep Colour" – defined in the HDMI 1.3 standard. ## Another Terminology: Colour Depth - **8-bit or 256 color displays:** Each screen pixel is represented by eight bits of memory. - The 256 colors are referenced to a “palette” or “index” (color lookup table, or CLUT). - The main point for eight-bit images is they can never contain more than 256 colors. - **Bit depth and color graphics files:** In their uncompressed states, eight-bit or 256-color image files dedicate eight bits to each color pixel in their respective images. ## Another Terminology: Color Depth - **24-bit “true color” displays:** Each screen pixel is represented by three groups of eight bits for a total of 24 bits. - A color image is typically represented by a bit depth ranging from 8 to 24 or higher. - **24-bit image:** The bits are divided into three groupings: 8 for red, 8 for green, and 8 for blue. - Combinations of these bits are used to represent other colors. - A 24-bit image offers 16.7 million (224) color values. ## Memory Requirements - **VGA example with a color depth of 8:** - Resolution = 640 x 480 = 307200 pixels. - Each pixel needs 8 bits (1 byte) = 300 kilobytes (307200/1024=300). - 8 bits color depth = 256 colors. ## Pixel data to RGB colour mapping: Direct representation - **Pixel data:** The number used to represent pixel data is composed of three numbers, one for each RGB colour. - **24-bit colour depth:** Consists of three 8-bit (1 byte) values representing RGB colour combinations. - This gives 256 colour values for each RGB colour. - **16-bit colour depth:** Consists of 3 fields for each RGB colour: - Red (5 bits), Green (6 bits), and blue (5 bits). - It gives 65,536 = 32x64x32 colour values for each RGB colour. ## Components of a Liquid Crystal Display (LCD) - A diagram of a liquid crystal display (LCD). - **Backlight:** Provides the source of light. - **Horizontal Polarising Filter:** Polarises the light horizontally. - **Active Transistor Matrix:** Controls the liquid crystal cell's voltage. - **Liquid Crystal:** The material that changes the polarization of light. - **RGB Colour Filters:** Filters light into its red, green, and blue components. - **Vertical Polarising Filter:** Allows only vertically polarized light to pass through. - **Process:** 1. **Light from the backlight passes through the horizontal polarising filter.** 2. **A charge is applied to a liquid crystal cell, changing the intensity of the RGB colour.** ## Simple graphics card components and operation - **Graphics card:** It processes video image data, sends it to Image Frame Buffer, converts RGB numerical values to voltage levels, and sends it to the display device synchronized to the dot clock. - **Problem:** How does the graphics card handle high-speed video games with lots of pixels? ## Speed / Memory Improvements: Coprocessors & GPUs - **The CPU** was responsible for performing the calculations needed to produce pixel colour values. - **Pixel value data:** Sent over the external bus to the graphics card frame buffers. - **The graphics card:** It took time for the calculations to be completed. - **Transfer** of pixel colour values to the graphics card had an impact on CPU performance. ## Speed / Memory Improvements: Coprocessors & GPUs - **GPU Co-processors (graphics accelerators):** Powerful and fast CPUs that were introduced onto graphics cards. - They are dedicated to performing the pixel colour calculations. - **The main CPU:** Still has to specify the information about the nature of the image to be produced ## Lets shrink the data - **Data compression:** Used to reduce the amount of data required to send or store an image. - This improves the throughput of images in the system. - **Data compression algorithms:** Reduce data size while maintaining acceptable levels of quality. - **Lossless:** Original values can be fully recovered when data is decompressed. - **Lossy:** Compression reduces data size at the expense of some quality degradation when the image is decompressed. ## Floating Point Numbers - **IEEE754 standard:** Represents floating point numbers in a standard format. - **Write the number in the format:** - **S:** Sign bit (0 = positive, 1 = negative). - **E:** Exponent (8-bit single precision, 11-bit double precision). - **B:** Exponent Bias (127 for single precision, 1023 for double precision). - **M:** Mantissa (23 bits for single precision, 52 bits for double precision). - Stored in memory with the least significant byte first (little endian format). ## Using Text - **Telex (1926):** Original Telex required characters and control codes to be sent, such as "a" and BELL. - **ASCII:** To save text on a computer, we use ASCII (American Standard Code for Information Interchange). ## Extended ASCII and Unicode - **ASCII:** Extended to include European characters. - **Unicode:** Defined to allow font, characters, symbols, and more. - Different formats: 32bit, 16 bit, 8 bit UTF-64, UTF-128, UTF-256, UTF-384, UTF-512 etc. ## Computer Misuse Act 1990 - It governs how individuals can lawfully access data on a machine. - **Unauthorised access:** - Unauthorised access to computer material. - Unauthorised access with intent to commit further offenses. - Unauthorised access with intent to impair, or with recklessness as to impairing, operation of computer, etc. ## Computer Misuse Act 1990 - **The Computer Misuse Act:** Protects personal data held by organisations from unauthorized access and modification. - **Illegal activities:** - **Unauthorised access:** Entering a computer system without permission (hacking). - **Unauthorised access with intent:** Entering a computer system to steal data or destroy a device or network (e.g., planting a virus). - **Unauthorised modification:** Modifying or deleting data, introducing malware or spyware onto a computer (electronic vandalism). - **Making, supplying, or obtaining anything:** Using it in computer misuse offenses. - **Offences:** Hacking, computer fraud, blackmail, and viruses. ## Data Protection Act 1998 - **UK Legislation:** Sets out guidelines on handling personal information. - **Appropriate measures:** Safeguarding personal information during examinations. - **Exemptions:** - Prevention/detection of criminal activities. - Assessment/collection of tax duties. - Safeguarding national security. ## Environmental Issues To Consider - **Main areas of concern:** - Usage of Earth's natural resources. - Consumption of energy. - Waste from the manufacturing process. - Waste from redundant/old technology. - Creation of a disposable society. - Environmental benefits from computing.