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C952 Computer Architecture PGKO Pre-Assessment Practice Questions, Exams of Computer Architecture and Organization Personal computer (PC) - ANSWERA computer designed for use by an individual, usually incorporating a graphics display, a keyboard, and a mouse. Server - ANSWERA computer used for running larger programs for multiple users, often simultaneously, and typically accessed only via a network. Supercomputer: - ANSWERA 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: - ANSWERA computer inside another device used for running one predetermined application or collection of software. Personal mobile devices (PMDs) - ANSWERare 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. Cloud computing - ANSWERrefers 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) - ANSWERdelivers 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 - ANSWERA microprocessor containing multiple processors ("cores") in a single integrated circuit. Acronym - ANSWERA word constructed by taking the initial letters of a string of words. For example: RAM is an acronym for Random Access Memory, and CPU is an acronym for Central Processing Unit. Terabyte (TB): - ANSWEROriginally 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. To reduce confusion, we now use the term tebibyte (TiB) for 240 bytes, defining terabyte (TB) to mean 1012 bytes. The figure below shows the full range of decimal and binary values and names. Systems software: - ANSWERSoftware that provides services that are commonly useful, including operating systems, compilers, loaders, and assemblers. Operating system - ANSWERSupervising program that manages the resources of a computer for the benefit of the programs that run on that computer. Compiler - ANSWERA program that translates high-level language statements into assembly language statements.
Active matrix display - ANSWERA liquid crystal display using a transistor to control the transmission of light at each individual pixel. Pixel - ANSWERThe smallest individual picture element. Screens are composed of hundreds of thousands to millions of pixels, organized in a matrix. Integrated circuit - ANSWERAlso called a chip. A device combining dozens to millions of transistors. Central processor unit (CPU) - ANSWERAlso 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 - ANSWERThe component of the processor that performs arithmetic operations. Control - ANSWERThe component of the processor that commands the datapath, memory, and I/O devices according to the instructions of the program. Memory - ANSWERThe 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) - ANSWERMemory 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 - ANSWERA small, fast memory that acts as a buffer for a slower, larger memory. Static random access memory (SRAM): - ANSWERAlso memory built as an integrated circuit, but faster and less dense than DRAM. Instruction set architecture - ANSWERAlso 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) - ANSWERThe 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 - ANSWERHardware that obeys the architecture abstraction Volatile memory - ANSWERStorage, such as DRAM, that retains data only if it is receiving power. Nonvolatile memory - ANSWERA 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 - ANSWERAlso called primary memory. Memory used to hold programs while they are running; typically consists of DRAM in today's computers.
Semiconductor - ANSWERA substance that does not conduct electricity well. Silicon crystal ingot - ANSWERA rod composed of a silicon crystal that is between 8 and 12 inches in diameter and about 12 to 24 inches long. Wafer - ANSWERA slice from a silicon ingot no more than 0.1 inches thick, used to create chips Defect - ANSWERA microscopic flaw in a wafer or in patterning steps that can result in the failure of the die containing that defect. Die: - ANSWERThe individual rectangular sections that are cut from a wafer, more informally known as chips. Yield - ANSWERThe percentage of good dies from the total number of dies on the wafer. Response time - ANSWERAlso 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 - ANSWERAlso called bandwidth. Another measure of performance, it is the number of tasks completed per unit time. CPU execution time - ANSWERAlso called CPU time. The actual time the CPU spends computing for a specific task
User CPU time - ANSWERThe CPU time spent in a program itself System CPU time - ANSWERThe CPU time spent in the operating system performing tasks on behalf of the program. Clock cycle: - ANSWERAlso 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 - ANSWERThe length of each clock cycle Clock cycles per instruction (CPI): - ANSWERAverage number of clock cycles per instruction for a program or program fragment. Instruction count - ANSWERThe number of instructions executed by the program. Instruction mix: - ANSWERA measure of the dynamic frequency of instructions across one or many programs. Workload - ANSWERA set of programs run on a computer that is either the actual collection of applications run by a user or constructed from real programs to approximate such a mix. A typical workload specifies both the programs and the relative frequencies. Benchmark - ANSWERA program selected for use in comparing computer performance.
Alignment restriction - ANSWERA requirement that data be aligned in memory on natural boundaries. Binary digit - ANSWERAlso called binary bit. One of the two numbers in base 2, 0 or 1, that are the components of information. Least significant bit - ANSWERThe rightmost bit in an LEGv8 doubleword Most significant bit - ANSWERThe leftmost bit in an LEGv8 doubleword. Two's complement - ANSWERA 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 (explained further below). One's complement - ANSWERA 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 - ANSWERA 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.
Instruction format - ANSWERA form of representation of an instruction composed of fields of binary numbers. Machine language - ANSWERBinary representation used for communication within a computer system. Hexadecimal - ANSWERNumbers in base 16 Opcode - ANSWERThe field that denotes the operation and format of an instruction. AND - ANSWERA logical bit- by-bit operation with two operands that calculates a 1 only if there is a 1 in both operands. OR - ANSWERA logical bit-by-bit operation with two operands that calculates a 1 if there is a 1 in either operand. NOT - ANSWERA 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 - ANSWERA 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 - ANSWERAn 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.
Stack - ANSWERA data structure for spilling registers organized as a last-in- first-out queue. Stack pointer - ANSWERA value denoting the most recently allocated address in a stack that shows where registers should be spilled or where old register values can be found. In LEGv8, it is register SP. Push - ANSWERAdd element to stack Pop - ANSWERRemove element from stack. Global pointer - ANSWERThe register that is reserved to point to the static area Procedure frame - ANSWERAlso called activation record. The segment of the stack containing a procedure's saved registers and local variables Frame pointer - ANSWERA value denoting the location of the saved registers and local variables for a given procedure. Text segment - ANSWERThe segment of a UNIX object file that contains the machine language code for routines in the source file PC-relative addressing - ANSWERAn addressing regime in which the address is the sum of the program counter (PC) and a constant in the instruction.
Addressing mode - ANSWEROne of several addressing regimes delimited by their varied use of operands and/or addresses. Data race - ANSWERTwo memory accesses form a data race if they are from different threads to same location, at least one is a write, and they occur one after another. Assembly language - ANSWERA symbolic language that can be translated into binary machine language. Pseudoinstruction - ANSWERA common variation of assembly language instructions often treated as if it were an instruction in its own right. Symbol table - ANSWERA table that matches names of labels to the addresses of the memory words that instructions occupy. Linker - ANSWERAlso called link editor. A systems program that combines independently assembled machine language programs and resolves all undefined labels into an executable file. Executable file - ANSWERA functional program in the format of an object file that contains no unresolved references. It can contain symbol tables and debugging information. A "stripped executable" does not contain that information. Relocation information may be included for the loader. Loader - ANSWERA systems program that places an object program in main memory so that it is ready to execute.
General-purpose register (GPR): - ANSWERA register that can be used for addresses or for data with virtually any instruction. Accumulator: - ANSWERArchaic term for register. On-line use of it as a synonym for "register" is a fairly reliable indication that the user has been around quite a while. Load-store architecture - ANSWERAlso called register-register architecture. An instruction set architecture in which all operations are between registers and data memory may only be accessed via loads or stores. Arithmetic Logic Unit (ALU) - ANSWERHardware that performs addition, subtraction, and usually logical operations such as AND and OR Dividend: - ANSWERA number being divided. Divisor: - ANSWERA number that the dividend is divided by. Quotient: - ANSWERThe primary result of a division; a number that when multiplied by the divisor and added to the remainder produces the dividend. Remainder - ANSWERThe secondary result of a division; a number that when added to the product of the quotient and the divisor produces the dividend. Scientific notation - ANSWERA notation that renders numbers with a single digit to the left of the decimal point.
Normalized - ANSWERA number in floating-point notation that has no leading 0s Floating point - ANSWERComputer arithmetic that represents numbers in which the binary point is not fixed Fraction: - ANSWERThe value, generally between 0 and 1, placed in the fraction field. The fraction is also called the mantissa. Exponent - ANSWERIn the numerical representation system of floating-point arithmetic, the value that is placed in the exponent field Overflow (floating-point) - ANSWERA situation in which a positive exponent becomes too large to fit in the exponent field. Underflow (floating-point): - ANSWERA situation in which a negative exponent becomes too large to fit in the exponent field. Double precision: - ANSWERA floating-point value represented in a 64-bit doubleword. Single precision - ANSWERA floating-point value represented in a 32-bit word Exception - ANSWERAlso called interrupt. An unscheduled event that disrupts program execution; used to detect overflow.
Clocking methodology - ANSWERThe approach used to determine when data is valid and stable relative to the clock. Edge-triggered clocking: - ANSWERA clocking scheme in which all state changes occur on a clock edge. Control signal - ANSWERA signal used for multiplexor selection or for directing the operation of a functional unit; contrasts with a data signal, which contains information that is operated on by a functional unit. Asserted: - ANSWERThe signal is logically high or true. Deasserted: - ANSWERThe signal is logically low or false Datapath element - ANSWERA unit used to operate on or hold data within a processor. In the LEGv8 implementation, the datapath elements include the instruction and data memories, the register file, the ALU, and adders. Program counter (PC): - ANSWERThe register containing the address of the instruction in the program being executed. Register file - ANSWERA state element that consists of a set of registers that can be read and written by supplying a register number to be accessed. Sign-extend - ANSWERTo increase the size of a data item by replicating the high-order sign bit of the original data item in the high-order bits of the larger, destination data item.
Branch target address - ANSWERThe address specified in a branch, which becomes the new program counter (PC) if the branch is taken. In the LEGv architecture, the branch target is given by the sum of the offset field of the instruction and the address of the branch. Branch taken - ANSWERA branch where the branch condition is satisfied and the program counter (PC) becomes the branch target. All unconditional branches are taken branches. Branch not taken or (untaken branch): - ANSWERA branch where the branch condition is false and the program counter (PC) becomes the address of the instruction that sequentially follows the branch. Truth table - ANSWERFrom logic, a representation of a logical operation by listing all the values of the inputs and then in each case showing what the resulting outputs should be. Don't-care term: - ANSWERAn element of a logical function in which the output does not depend on the values of all the inputs. Don't-care terms may be specified in different ways. Opcode: - ANSWERThe field that denotes the operation and format of an instruction. Single-cycle implementation - ANSWERAlso called single clock cycle implementation. An implementation in which an instruction is executed in one clock cycle. While easy to understand, it is too slow to be practical.
