Computer Architecture

Register File

A state element that consists of a set of registers that can be read and written by supplying a register number to be accessed.

provides 1024 scalar 32-bit registers for up to 64 threads.

machine language

The language made up of binary-coded instructions that is used directly by the computer

system software

The set of programs that enables a computer's hardware devices and application software to work together; it includes the operating system and utility programs.

operating system

(computer science) software that controls the execution of computer programs and may provide various services

Assembly Language

Programming language that has the same structure and set of commands as machine languages but allows programmers to use symbolic representations of numeric machine code.

IBM 360/91

Introduced many new concepts, including dynamic detection of memory hazards, generalized forwarding, and reservation stations. Tomasulo's algorithm

The internal organization of the 360/91 shares many features with the Pentium III and Pentium 4, as well as with several other microprocessors. One major difference was that there was no branch prediction in the 360/91 and hence no speculation. Another major difference was that there was no commit unit, so once the instructions finished execution, they updated the registers.

Dynamic Random Access Memory (DRAM)

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.

Multiple DRAMs are used together to contain the instructions and data of a program. In contrast to sequential access memories, such as magnetic tapes, the RAM portion of the term DRAM means that memory accesses take basically the same amount of time no matter what portion of the memory is read.

Modern DRAMS consist of rows in each bank

frame buffering

A portion of RAM containing a bitmap that drives a video display. It is a memory buffer containing a complete frame of data.

The image to be represented onscreen is stored in the frame buffer, and the bit pattern per pixel is read out to the graphics display at the refresh rate. The animation below shows a frame buffer with a simplified design of just 4 bits per pixel.

Datapath

The component of the processor that performs arithmetic operations

Control

The component of the processor that commands the datapath, memory, and I/O devices according to the instructions of the program.

Integrated circuit

Also called a chip. A device combining dozens to millions of transistors.

Central processor unit (CPU)

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.

Static random access memory (SRAM)

Also memory built as an integrated circuit, but faster and less dense than DRAM.

Instruction set architecture

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)

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.

Volatile memory

Storage, such as DRAM, that retains data only if it is receiving power.

Nonvolatile Memory

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.

Magnetic disk

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

Main memory

Also called primary memory. Memory used to hold programs while they are running; typically consists of DRAM in today's computers.

Secondary memory

Nonvolatile memory used to store programs and data between runs; typically consists of flash memory in PMDs and magnetic disks in servers.

Flash memory

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.

Single Instruction Single Data (SISD)

A uniprocessor

Multiple Instruction Multiple Data (MIMD)

A multiprocessor.

Single Program, Multiple Data Streams (SPMD)

The conventional MIMD programming model, where a single program runs across all processors.

Single Instruction Stream, Multiple Data Streams (SIMD)

The same instruction is applied to many data streams, as in a vector processor.

Data-level parallelism

Parallelism achieved by performing the same operation on independent data

vector-based code

conventional code

LEGv8

assembly instructions

multimedia extensions (MMX)

An expanded set of instructions supported by a processor that provides multimedia-specific functions.

data hazard (pipeline data hazard)

When a planned instruction cannot execute in the proper clock cycle because data that is needed to execute the instruction are not yet available.

forwarding (bypassing)

A method of resolving a data hazard by retrieving the missing data element from internal buffers rather than waiting for it to arrive from programmer-visible registers or memory

Structural hazard

When a planned instruction cannot execute in the proper clock cycle because the hardware does not support the combination of instructions that are set to execute.

Pipelining

Technique that allows the CPU to work on more than one instruction at a time

Formula

total process time \= [longest task * (total load -1)] + total load time

R-format ALU operations

Requires register file and the ALU.

Program Counter (PC)

The register that contains the address of the next instruction to be executed

output

The results of the operation of any system.

temporal locality

The principle stating that if a data location is referenced then it will tend to be referenced again soon.

spatial locality

The principle stating that if a data location is referenced, data locations with nearby addresses will tend to be referenced soon.

Memory hierarchy

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)

The minimum unit of information that can be either present or not present in a cache.

Hit rate

The fraction of memory accesses found in a level of the memory hierarchy.

Miss rate

The fraction of memory accesses not found in a level of the memory hierarchy

miss penalty

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 requestor.

Hit time

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.

Parallelization

consist of dividing a program into separate components that run in parallel on individual computers in the cluster

superscalar

Technique primarily associated with hardware.

Functional units (ALU, Floating Point Unit, Load/Store Unit) are duplicated in the pipeline of a superscalar processor which allows the hardware to issue multiple instructions to each unit simultaneously.

ARM architecture

can support 16-bit

Amdahl's Law

A formula used to find the maximum improvement possible by improving a particular part of a system. In parallel computing, Amdahl's law is mainly used to predict the theoretical maximum speedup for program processing using multiple processors

multiprocessor

A term used to refer to a computer with more than one CPU.

Uniform Memory Access (UMA)

A multiprocessor in which latency to any word in main memory is about the same no matter which processor requests the access.

Non-Uniform Memory Access (NUMA)

Varying system memory access times, because of system hardware.

loop unrolling

A technique to get more performance from loops that access arrays, in which multiple copies of the loop body are made and instructions from different iterations are scheduled together.

Blocking

a failure to retrieve information that is available in memory even though you are trying to produce it

can help reduce cache miss rate

Set Associative Cache

A cache that has a fixed number of locations (at least two) where each block can be placed.

RAID 0 (Disk Striping)

Disk Striping. Disk striping requires at least two drives. It does not provide redundancy to data. If any one drive fails, all data is lost.

RAID 1 (mirroring)

Two drives are used in unison, and all data is written to both drives, giving you a mirror or extra copy of the data, in the case that one drive fails

RAID 2

Bit-level striping with dedicated Hamming-code parity. OBSOLETE.

RAID 3

Byte-level striping with dedicated parity. OBSOLETE, replaced with RAID 5.

RAID 4

Block-level striping with dedicated parity. Not often used, replaced with RAID 5.

RAID 5

Disk striping with parity. RAID-5 uses three or more disks and provides fault tolerance.

RAID 6

Disk striping with parity. RAID-6 uses four or more disks and provides fault tolerance. It can survive the failure of two drives.

silicon crystal ingot

A rod composed of a silicon crystal that is between 8 and 12 inches in diameter and about 12 to 24 inches long.

wafer

A slice from a silicon ingot no more than 0.1 inches thick, used to create chips.

Instruction Set Architecture (ISA)

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)

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.

Transistor

An on/off switch controlled by an electric signal

very large-scale integrated (VLSI) circuit

A device containing hundreds of thousands to millions of transistors.

silicon

A natural element that is a semiconductor

1. Excellent conductors of electricity (using either microscopic copper or aluminum wire)

2. Excellent insulators from electricity (like plastic sheathing or glass)

3. Areas that can conduct or insulate under special conditions (as a switch)

Semiconductor

A substance that can conduct electricity under some conditions

Die

The individual rectangular sections that are cut from a wafer, more informally known as chips.

complementary metal-oxide semiconductor (CMOS)

Dominant technology for integrated circuits

LEGv8

Assembly Language

LEGv8 word

A natural unit of access in a computer, usually a group of 32 bits

LEGv8 doubleword

Another natural unit of access in a computer, usually a group of 64 bits (8 bytes); corresponds to the size of a register in the LEGv8 architecture

LEGv8 register

64 bits wide