WGU C952 Computer Architecture Terms to Know; Explained Correctly

WGU C952 Computer Architecture Terms to Know; Explained Correctly WGU C952 Computer Architecture Terms to Know; Explained Correctly Information revolution correct answer Computers have led to a third revolution for civilization, with the _________________ taking its place alongside the agricultural and the industrial revolutions. Personal Computer (PC) correct answer A computer designed for use by an individual, usually incorporating a graphics display, a keyboard, and a mouse. Server correct answer A computer used for running larger programs for multiple users, often simultaneously, and typically accessed only via a network. Supercomputer correct answer A class of computers with the highest performance and cost; they are configured as servers and typically cost tens to hundreds of millions of dollars. Embedded computer correct answer A computer inside another device used for running one predetermined application or collection of software. processor cores correct answer Many embedded processors are designed using ______________, a version of a processor written in a hardware description language, such as Verilog or VHDL. Personal mobile devices (PMDs) correct answer are small wireless devices to connect to the Internet; they rely on batteries for power, and software is installed by downloading apps. Conventional examples are smart phones and tablets. Warehouse Scale Computers (WSCs) correct answer Taking over from the conventional server is Cloud Computing, which relies upon giant datacenters that are now known as__________________________ Cloud computing correct answer refers to large collections of servers that provide services over the Internet; some providers rent dynamically varying numbers of servers as a utility. Software as a Service (SaaS) correct answer delivers software and data as a service over the Internet, usually via a thin program such as a browser that runs on local client devices, instead of binary code that must be installed, and runs wholly on that device. Examples include web search and social networking. Multicore microprocessor: correct answer A microprocessor containing multiple processors ("cores") in a single integrated circuit. Terabyte (TB): correct answer Originally 1,099,511,627,776 (240) bytes, although communications and secondary storage systems developers started using the term to mean 1,000,000,000,000 (1012) bytes. tebibyte (TiB) correct answer To reduce confusion, we now use the term _______________ for 240 bytes, defining terabyte (TB) to mean 1012 bytes. Moore's Law . correct answer __________________ states that integrated circuit resources double every 18-24 months abstractions correct answer A major productivity technique for hardware and software is to use________________ to characterize the design at different levels of representation; lower-level details are hidden to offer a simpler model at higher levels. common case correct answer Making the________________ fast will tend to enhance performance better than optimizing the rare case. parallel correct answer Since the dawn of computing, computer architects have offered designs that get more performance by computing operations in _______________. pipelining correct answer A particular pattern of parallelism is so prevalent in computer architecture that it merits its own name: _______________ , which moves multiple operations through hardware units that each do a piece of an operation, akin to water flowing through a pipeline. prediction correct answer The idea of _________________ is that, in some cases it can be faster on average to guess and start working rather than wait until you know for sure, assuming that the mechanism to recover from a misprediction is not too expensive and your prediction is relatively accurate. hierarchy of memories correct answer Architects have found that they can address conflicting demands of fast, large, and cheap memory with a hierarchy of memories, with the fastest, smallest, and most expensive memory per bit at the top of the hierarchy and the slowest, largest, and cheapest per bit at the bottom. dependable correct answer Since any physical device can fail, we make systems dependable by including redundant components that can take over when a failure occurs and to help detect failures. Systems software correct answer Software that provides services that are commonly useful, including operating systems, compilers, loaders, and assemblers. Operating system correct answer Supervising program that manages the resources of a computer for the benefit of the programs that run on that computer. Compiler correct answer A program that translates high-level language statements into assembly language statements. binary numbers correct answer The two symbols for these two letters are the numbers 0 and 1, and we commonly think of the computer language as numbers in base 2, or binary numbers. Binary digit correct answer Also called a bit. One of the two numbers in base 2 (0 or 1) that are the components of information. Instruction correct answer A command that computer hardware understands and obeys Assembler correct answer A program that translates a symbolic version of instructions into the binary version. Assembly language correct answer A symbolic representation of machine instructions. Machine language correct answer A binary representation of machine instructions. High-level programming language correct answer A portable language such as C, C++, Java, or Visual Basic that is composed of words and algebraic notation that can be translated by a compiler into assembly language. Input device correct answer A mechanism through which the computer is fed information, such as a keyboard. Output device correct answer A mechanism that conveys the result of a computation to a user, such as a display, or to another computer. liquid crystal display (LCD) correct answer A display technology using a thin layer of liquid polymers that can be used to transmit or block light according to whether a charge is applied. Active matrix display correct answer A liquid crystal display using a transistor to control the transmission of light at each individual pixel. bit map correct answer The image is composed of a matrix of picture elements, or pixels, which can be represented as a matrix of bits, called a ____________ Pixel correct answer The smallest individual picture element. Screens are composed of hundreds of thousands to millions of pixels, organized in a matrix. raster refresh buffer correct answer The computer hardware support for graphics consists mainly of a raster refresh buffer, or frame buffer, to store the bit map. Integrated circuit correct answer Also called a chip. A device combining dozens to millions of transistors. Central processor unit (CPU): correct answer Also called processor. The active part of the computer, which contains the datapath and control and which adds numbers, tests numbers, signals I/O devices to activate, and so on. Datapath correct answer The component of the processor that performs arithmetic operations. Control correct answer The component of the processor that commands the datapath, memory, and I/O devices according to the instructions of the program. Memory correct answer The storage area in which programs are kept when they are running and that contains the data needed by the running programs. Dynamic random access memory (DRAM): correct answer Memory built as an integrated circuit; it provides random access to any location. Access times are 50 nanoseconds and cost per gigabyte in 2012 was $5 to $10. Cache memory: correct answer A small, fast memory that acts as a buffer for a slower, larger memory. Static random access memory (SRAM) correct answer Also memory built as an integrated circuit, but faster and less dense than DRAM. Instruction set architecture correct answer Also called architecture. An abstract interface between the hardware and the lowest-level software that encompasses all the information necessary to write a machine language program that will run correctly, including instructions, registers, memory access, I/O, and so on. Application binary interface (ABI): correct answer The user portion of the instruction set plus the operating system interfaces used by application programmers. It defines a standard for binary portability across computers. Implementation correct answer Hardware that obeys the architecture abstraction. volatile memory correct answer Storage, such as DRAM, that retains data only if it is receiving power. Nonvolatile memory correct answer A form of memory that retains data even in the absence of a power source and that is used to store programs between runs. A DVD disk is nonvolatile. Main memory correct answer Also called primary memory. Memory used to hold programs while they are running; typically consists of DRAM in today's computers. Secondary memory: correct answer Nonvolatile memory used to store programs and data between runs; typically consists of flash memory in PMDs and magnetic disks in servers. Magnetic disk correct answer Also called hard disk. A form of nonvolatile secondary memory composed of rotating platters coated with a magnetic recording material. Because they are rotating mechanical devices, access times are about 5 to 20 milliseconds and cost per gigabyte in 2012 was $0.05 to $0.10. Flash memory correct answer A nonvolatile semiconductor memory. It is cheaper and slower than DRAM but more expensive per bit and faster than magnetic disks. Access times are about 5 to 50 microseconds and cost per gigabyte in 2012 was $0.75 to $1.00. networks correct answer interconnect whole computers, allowing computer users to extend the power of computing by including communication. Local area network (LAN): correct answer A network designed to carry data within a geographically confined area, typically within a single building. Wide area network (WAN): correct answer A network extended over hundreds of kilometers that can span a continent. Transistor correct answer An on/off switch controlled by an electric signal. Very large-scale integrated (VLSI) circuit: correct answer A device containing hundreds of thousands to millions of transistors. Silicon: correct answer A natural element that is a semiconductor. Semiconductor: correct answer A substance that does not conduct electricity well. Silicon crystal ingot: correct answer A rod composed of a silicon crystal that is between 8 and 12 inches in diameter and about 12 to 24 inches long. Wafer: correct answer A slice from a silicon ingot no more than 0.1 inches thick, used to create chips. Defect correct answer A microscopic flaw in a wafer or in patterning steps that can result in the failure of the die containing that defect. Die: (also called chips) correct answer The individual rectangular sections that are cut from a wafer, more informally known as chips. Yield: correct answer The percentage of good dies from the total number of dies on the wafer. Response time: correct answer Also called execution time. The total time required for the computer to complete a task, including disk accesses, memory accesses, I/O activities, operating system overhead, CPU execution time, and so on. Throughput: correct answer Also called bandwidth. Another measure of performance, it is the number of tasks completed per unit time. Time correct answer is the measure of computer performance: the computer that performs the same amount of work in the least time is the fastest. Wall Clock Time (also called Response Time or Elapsed Time) correct answer The most straightforward definition of time is called ______________, response time, or elapsed time. These terms mean the total time to complete a task, including disk accesses, memory accesses, input/output (I/O) activities, operating system overhead—everything. CPU execution time correct answer Also called CPU time. The actual time the CPU spends computing for a specific task. User CPU time: correct answer The CPU time spent in a program itself. System CPU time: correct answer The CPU time spent in the operating system performing tasks on behalf of the program. system performance (CPU Performance) correct answer refers to elapsed time on an unloaded ______________ to refer to user CPU time. Clock rate correct answer is the inverse of the clock period (clock cycle). Clock cycle correct answer Also called tick, clock tick, clock period, clock, or cycle. The time for one clock period, usually of the processor clock, which runs at a constant rate. Clock period correct answer The length of each clock cycle. Clock cycles per instruction (CPI): correct answer Average number of clock cycles per instruction for a program or program fragment. Instruction count: correct answer The number of instructions executed by the program. Instruction mix: correct answer A measure of the dynamic frequency of instructions across one or many programs. (IPC) Instructions Per Clock Cycle correct answer Some designers invert CPI to talk about IPC, or instructions per clock cycle. If a processor executes on average two instructions per clock cycle, then it has an IPC of 2 and hence a CPI of 0.5. Instruction set correct answer The vocabulary of commands understood by a given architecture. Stored-program concept: correct answer The idea that instructions and data of many types can be stored in memory as numbers and thus be easy to change, leading to the stored-program computer. comments correct answer The words to the right of the double slashes (//) on each line are comments for the human reader, so the computer ignores them. Word: correct answer A natural unit of access in a computer, usually a group of 32 bits. Doubleword: correct answer Another natural unit of access in a computer, usually a group of 64 bits; corresponds to the size of a register in the LEGv8 architecture. Data transfer instruction: correct answer A command that moves data between memory and registers. Address : correct answer A value used to delineate the location of a specific data element within a memory array. load correct answer The data transfer instruction that copies data from memory to a register is traditionally called ___________ base address correct answer is the starting address of an array in memory. base register correct answer is a register that holds an array's base address. offset correct answer is a constant value added to a base address to locate a particular array element. spilling registers correct answer The process of putting less frequently used variables (or those needed later) into memory is called ________ Binary digit correct answer Also called binary bit. One of the two numbers in base 2, 0 or 1, that are the components of information. Least significant bit correct answer The rightmost bit in an LEGv8 doubleword. Most significant bit correct answer The leftmost bit in an LEGv8 doubleword.. overflow correct answer If the number that is the proper result of such operations cannot be represented by these rightmost hardware bits, _________ is said to have occurred. sign and magnitude representation correct answer is a signed number representation where a single bit is used to represent the sign, and the remaining bits represent the the magnitude. Two's complement Two's complement: correct answer A signed number representation where a leading 0 indicates a positive number and a leading 1 indicates a negative number. The complement of a value is obtained by complementing each bit (0 → 1 or 1 → 0), and then adding one to the result. sign extension correct answer The function of a signed load is to copy the sign repeatedly to fill the rest of the register, known as a ____________________. One's complement One's complement: correct answer A notation that represents the most negative value by 10 ... 000two and the most positive value by 01 ... 11two, leaving an equal number of negatives and positives but ending up with two zeros, one positive (00 ... 00two) and one negative (11 ... 11two). The term is also used to mean the inversion of every bit in a pattern: 0 to 1 and 1 to 0. Biased notation Biased notation: correct answer A notation that represents the most negative value by 00 ... 000two and the most positive value by 11 ... 11two, with 0 typically having the value 10 ... 00two, thereby biasing the number such that the number plus the bias has a non-negative representation. fields correct answer A machine instruction is composed of fields, each field having several bits and representing some part of the instruction. Instruction format Instruction format: correct answer A form of representation of an instruction composed of fields of binary numbers. Hexadecimal Hexadecimal: correct answer Numbers in base 16. Opcode Opcode: correct answer The field that denotes the operation and format of an instruction. destination register correct answer A _________________ is a register that receives the result of an operation. shift correct answer moves all the bits in a doubleword to the left or right, filling the emptied bits with 0s. AND AND: correct answer A logical bit- by-bit operation with two operands that calculates a 1 only if there is a 1 in both operands. mask correct answer AND can apply a bit pattern to a set of bits to force 0s where there is a 0 in the bit pattern. Such a bit pattern in conjunction with AND is traditionally called a mask, since the mask "conceals" some bits. OR OR: correct answer A logical bit-by-bit operation with two operands that calculates a 1 if there is a 1 in either operand. NOT NOT: correct answer A logical bit-by-bit operation with one operand that inverts the bits; that is, it replaces every 1 with a 0, and every 0 with a 1. EOR EOR: correct answer A logical bit-by-bit operation with two operands that calculates the exclusive OR of the two operands. That is, it calculates a 1 only if the values are different in the two operands. Conditional branch Conditional branch: correct answer An instruction that tests a value and that allows for a subsequent transfer of control to a new address in the program based on the outcome of the test. Branch address table Branch address table: correct answer Also called branch table. A table of addresses of alternative instruction sequences. Arithmetic Logic Unit Arithmetic Logic Unit (ALU): correct answer Hardware that performs addition, subtraction, and usually logical operations such as AND and OR. Scientific notation Scientific notation: correct answer A notation that renders numbers with a single digit to the left of the decimal point. Normalized Normalized: correct answer A number in floating-point notation that has no leading 0s. Floating point Floating point: correct answer Computer arithmetic that represents numbers in which the binary point is not fixed. Fraction Fraction: correct answer The value, generally between 0 and 1, placed in the fraction field. The fraction is also called the mantissa. Exponent Exponent: correct answer In the numerical representation system of floating-point arithmetic, the value that is placed in the exponent field. Overflow (floating-point) Overflow (floating-point): correct answer A situation in which a positive exponent becomes too large to fit in the exponent field. Underflow (floating-point) Underflow (floating-point): correct answer A situation in which a negative exponent becomes too large to fit in the exponent field. Double precision Double precision: correct answer A floating-point value represented in a 64-bit doubleword. Single precision Single precision: correct answer A floating-point value represented in a 32-bit word. Exception Exception: correct answer Also called interrupt. An unscheduled event that disrupts program execution; used to detect overflow. Interrupt Interrupt: correct answer An exception that comes from outside of the processer. (Some architectures use the term interrupt for all exceptions. Not a Number (NaN) correct answer IEEE 754 even has a symbol for the result of invalid operations, such as 0/0 or subtracting infinity from infinity. This symbol is _______________ Guard Guard: correct answer The first of two extra bits kept on the right during intermediate calculations of floating-point numbers; used to improve rounding accuracy. Round Round: correct answer Method to make the intermediate floating-point result fit the floating-point format; the goal is typically to find the nearest number that can be represented in the format. It is also the name of the second of two extra bits kept on the right during intermediate floating-point calculations, which improves rounding accuracy. Units in the last place Units in the last place (ulp): correct answer The number of bits in error in the least significant bits of the significand between the actual number and the number that can be represented. Sticky bit Sticky bit: correct answer A bit used in rounding in addition to guard and round that is set whenever there are nonzero bits to the right of the round bit. Fused multiply add Fused multiply add: correct answer A floating-point instruction that performs both a multiply and an add, but rounds only once after the add. Temporal locality Temporal locality: correct answer The locality principle stating that if a data location is referenced then it will tend to be referenced again soon. Spatial locality Spatial locality: correct answer The locality principle stating that if a data location is referenced, data locations with nearby addresses will tend to be referenced soon. Memory hierarchy Memory hierarchy: correct answer A structure that uses multiple levels of memories; as the distance from the processor increases, the size of the memories and the access time both increase. Block (or line) Block (or line): correct answer The minimum unit of information that can be either present or not present in a cache. Hit rate Hit rate: correct answer The fraction of memory accesses found in a level of the memory hierarchy. Miss rate Miss rate: correct answer The fraction of memory accesses not found in a level of the memory hierarchy. Hit time Hit time: correct answer The time required to access a level of the memory hierarchy, including the time needed to determine whether the access is a hit or a miss. Miss penalty Miss penalty: correct answer The time required to fetch a block into a level of the memory hierarchy from the lower level, including the time to access the block, transmit it from one level to the other, insert it in the level that experienced the miss, and then pass the block to the requester. Flash memory Flash memory correct answer is a type of electrically erasable programmable read-only memory (EEPROM). Track Track: correct answer One of thousands of concentric circles that make up the surface of a magnetic disk. Sector Sector: correct answer One of the segments that make up a track on a magnetic disk; a sector is the smallest amount of information that is read or written on a disk. Seek Seek: correct answer The process of positioning a read/write head over the proper track on a disk. Rotational latency Rotational latency: correct answer Also called rotational delay. The time required for the desired sector of a disk to rotate under the read/write head; usually assumed to be half the rotation time. Direct-mapped cache Direct-mapped cache: correct answer A cache structure in which each memory location is mapped to exactly one location in the cache. Tag Tag: correct answer A field in a table used for a memory hierarchy that contains the address information required to identify whether the associated block in the hierarchy corresponds to a requested word. Valid bit Valid bit: correct answer A field in the tables of a memory hierarchy that indicates that the associated block in the hierarchy contains valid data. Cache miss Cache miss: correct answer A request for data from the cache that cannot be filled because the data are not present in the cache. Write-through Write-through: correct answer A scheme in which writes always update both the cache and the next lower level of the memory hierarchy, ensuring that data are always consistent between the two. Write buffer Write buffer: correct answer A queue that holds data while the data are waiting to be written to memory. Write-back Write-back: correct answer A scheme that handles writes by updating values only to the block in the cache, then writing the modified block to the lower level of the hierarchy when the block is replaced. Split cache Split cache: correct answer A scheme in which a level of the memory hierarchy is composed of two independent caches that operate in parallel with each other, with one handling instructions and one handling data. Fully associative cache Fully associative cache: correct answer A cache structure in which a block can be placed in any location in the cache. Set-associative cache Set-associative cache: correct answer A cache that has a fixed number of locations (at least two) where each block can be placed. Least recently used Least recently used (LRU): correct answer A replacement scheme in which the block replaced is the one that has been unused for the longest time. Multilevel cache Multilevel cache: correct answer A memory hierarchy with multiple levels of caches, rather than just a cache and main memory. Global miss rate Global miss rate: correct answer The fraction of references that miss in all levels of a mutlilevel cache. Local miss rate Local miss rate: correct answer The fraction of references to one level of a cache that miss; used in multilevel hierarchies. Error detection code Error detection code: correct answer A code that enables the detection of an error in data, but not the precise location and, hence, correction of the error. Virtual memory Virtual memory: correct answer A technique that uses main memory as a "cache" for secondary storage. Physical address Physical address: correct answer An address in main memory. Protection Protection: correct answer A set of mechanisms for ensuring that multiple processes sharing the processor, memory, or I/O devices cannot interfere, intentionally or unintentionally, with one another by reading or writing each other's data. These mechanisms also isolate the operating system from a user process. Page fault Page fault: correct answer An event that occurs when an accessed page is not present in main memory. Virtual address Virtual address: correct answer An address that corresponds to a location in virtual space and is translated by address mapping to a physical address when memory is accessed. Address translation Address translation: correct answer Also called address mapping. The process by which a virtual address is mapped to an address used to access memory. Segmentation Segmentation: correct answer A variable-size address mapping scheme in which an address consists of two parts: a segment number, which is mapped to a physical address, and a segment offset. Page table Page table: correct answer The table containing the virtual to physical address translations in a virtual memory system. The table, which is stored in memory, is typically indexed by the virtual page number; each entry in the table contains the physical page number for that virtual page if the page is currently in memory. Swap space Swap space: correct answer The space on the disk reserved for the full virtual memory space of a process. Reference bit Reference bit: correct answer Also called use bit or access bit. A field that is set whenever a page is accessed and that is used to implement LRU or other replacement schemes. Translation-lookaside buffer (TLB) Translation-lookaside buffer (TLB): correct answer A cache that keeps track of recently used address mappings to try to avoid an access to the page table. Virtually addressed cache Virtually addressed cache: correct answer A cache that is accessed with a virtual address rather than a physical address. Aliasing Aliasing: correct answer A situation in which two addresses access the same object; it can occur in virtual memory when there are two virtual addresses for the same physical page. Physically addressed cache Physically addressed cache: correct answer A cache that is addressed by a physical address. Supervisor mode Supervisor mode: correct answer Also called kernal mode. A mode indicating that a running process is an operating system process. System call System call: correct answer A special instruction that transfers control from user mode to a dedicated location in supervisor code space, invoking the exception mechanism in the process. Context switch Context switch: correct answer A changing of the internal state of the processor to allow a different process to use the processor that includes saving the state needed to return to the currently executing process. Exception enable Exception enable: correct answer Also called interrupt enable. A signal or action that controls whether the process responds to an exception or not; necessary for preventing the occurrence of exceptions during intervals before the processor has safely saved the state needed to restart. Restartable instruction Restartable instruction: correct answer An instruction that can resume execution after an exception is resolved without the exception's affecting the result of the instruction. Redundant arrays of inexpensive disks Redundant arrays of inexpensive disks (RAID): correct answer An organization of disks that uses an array of small and inexpensive disks so as to increase both performance and reliability. Striping Striping: correct answer Allocation of logically sequential blocks to separate disks to allow higher performance than a single disk can deliver. Mirroring Mirroring: correct answer Writing identical data to multiple disks to increase data availability. mathematical model A mathematical model correct answer is an equation used to represent data. variable A variable correct answer is a symbol representing data. Ex: T is a common variable representing temperature. independent variable An independent variable correct answer is a symbol representing an input. Ex: x is a common independent variable. A simple way to remember independent variables are for input is 'I' for independent and input.[c] . dependent variable A dependent variable correct answer is a symbol representing an output. Ex: y is a common dependent variable. parameters Parameters correct answer are added and adjusted. Ex: Data modeled to a line has two parameters, m and b, such that y = m ∙ x + b. trendline A trendline correct answer is a model that captures changes in data. Multiprocessor Multiprocessor: correct answer A computer system with at least two processors. This computer is in contrast to a uniprocessor, which has one, and is increasingly hard to find today. Task-level parallelism Task-level parallelism or process-level parallelism: correct answer Utilizing multiple processors by running independent programs simultaneously. Parallel processing program Parallel processing program: correct answer A single program that runs on multiple processors simultaneously. Cluster Cluster: correct answer A set of computers connected over a local area network that function as a single large multiprocessor. Shared memory multiprocessor Shared memory multiprocessor (SMP): correct answer A parallel processor with a single physical address space. Strong scaling Strong scaling: correct answer Speed-up achieved on a multiprocessor without increasing the size of the problem. Weak scaling Weak scaling: correct answer Speed-up achieved on a multiprocessor while increasing the size of the problem proportionally to the increase in the number of processors. SISD SISD or single instruction stream, single data stream correct answer single data stream: A uniprocessor. MIMD MIMD or multiple instruction streams, multiple data stream correct answer multiple data streams: A multiprocessor. SPMD SPMD or single program, multiple data streams: correct answer The conventional MIMD programming model, where a single program runs across all processors. SIMD SIMD or single instruction stream, multiple data streams: correct answer The same instruction is applied to many data streams, as in a vector processor. Data-level parallelism Data-level parallelism: correct answer Parallelism achieved by performing the same operation on independent data. Vector lane Vector lane: correct answer One or more vector functional units and a portion of the vector register file. Inspired by lanes on highways that increase traffic speed, multiple lanes execute vector operations simultaneously. Protection group Protection group: correct answer The group of data disks or blocks that share a common check disk or block. Hot-swapping Hot-swapping: correct answer Replacing a hardware component while the system is running. Standby spares Standby spares: correct answer Reserve hardware resources that can immediately take the place of a failed component. Error detecting and correcting code (RAID 2) correct answer borrows an error detection and correction scheme most often used for memories Bit-interleaved parity (RAID 3) correct answer is popular in applications with large data sets, such as multimedia and some scientific codes. Block-interleaved parity (RAID 4) correct answer uses the same ratio of data disks and check disks as RAID 3, but they access data differently. The parity is stored as blocks and associated with a set of data blocks. Distributed block-interleaved parity (RAID 5) correct answer allows multiple writes to occur simultaneously as long as the parity blocks are not located on the same disk. P + Q redundancy (RAID 6) correct answer Parity-based schemes protect against a single self-identifying failure.