AIT 542

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Memory Mapped IO supports:

16 bit address bus lines (used by an old microprocessor)

Main Memory

Byte addressable Flat, linear address space Typical sizes: 1 GB to 16 GB Volatile

Almost all memory now is

Byte-addressable - meaning each individual byte has an address - but can address larger packages: halfwords

Requires constant refreshing?

DRAM

Computers + Networks=

Platforms

BUS may have different masters T o F?

True

Computer memory that loses its contents when electrical power is lost, is said to be ________

Volatile

What is a memory that May require electrical power to hold a value:

Volatile memory

A bus is a collection of:

Wires connecting things.

What are serious security concerns with Data stores?

(1) theft of data or code, (2) insertion of data or code [e.g., Stuxnet, or malware introduced via USB device handshake

What does a 64 bit machine mean?

- CPU can do 64 bit number + 64 bit number - One register size is 64 bit - Data bus has 64 lanes - The address bus has more than 64 lanes.. because Memory -mapped I/O

An important feature of processors is their power consumption:

- Faster = more power - More power = hotter and shorter battery life (if battery is powered)

CPU

- Has registers and status words - Is bus master most of the time - May surrender BUS to other devices for brief intervals * Do simple things very fast

A basic computer is composed of which 5 components?

- Memory - Input Device - Output Device - CPU - Bus

What are 6 common features of platforms?

- Processor - Bus - Memory - Data store - I/O capabilities: network, user input/output - Power source

What is a BUS?

- Provides data and control signal connection between units - Transfers data between a source and a destination as requested by bus master - Can generate traps for certain conditions - Creates the address space: most addresses are in memory, some are I/O devices

Most semiconductor memory is volatile -

- only holds data so long as electrical power is maintained.

How high are typically cache hit ratios?

95% or better

Which of the following are considered to be non-volatile memory? Select all that apply A. Optical Drives B. USB Drives C. Magnetic Tape D. Cache

A,B,C

What is a cache hit?

Accessed location is in cache

Accessing cache is much faster than

Accessing main memory

Information technology is the study of? Select all that apply A. Information B. Infrastructure Hardware C. People D. Infrastructure Software

All

BUS is the main interconnect between

All interacting internal components of computer

Memories: Solid State Drives (SSDs)

Are peripheral devices Interact through interfaces / controllers Uses flash memory technology Now in capacities in TB, but $$ Non-volatile

Memories: Magnetic Tape

Are peripheral devices Interact through interfaces/controllers Now in 100s of GB Mechanical access method: tape must be moved to correct position Sequential (linear) access only Non-volatile Magnetics subject to magnetic fields

The _________ executes instructions retrieved from memory

CPU

Provides a queue for the CPU resulting to significant speed increases

Cache

CPU accesses an address: if not present in cache =

Cache miss

Computers have how many BUS?

Computers have at least one bus ..often > 1

Memories:Registers

Contained within CPU GPRs: General Purpose Registers PC: Program Counter PSW: Program Status Word Accessed at CPU speed Volatile

Memories; Disks

DISKS (magnetic, optical): Are peripheral devices Interact through interfaces/controllers Magnetics: TB Opticals: now in 10s of GB Mechanical access method (e.g., Read/write head must be moved to correct position) Non-volatile Magnetics subject to magnetic fields

Main Memory RAM:

Dynamic RAM needs constant refreshing as store values 'decay' over time and must be re-written, but it is the cheapest technology RAM to mass produce. Static RAM is random access memory that retains data bits in its memory as long as power is being supplied.

For all practical purposes, data, information and knowledge are essentially the same?

False

Programs are usually executed directly from main memory? T or F

False

For CPU, speed is measured in

How many instructions per second a CPU performs - Usually in million instructions per second (MIPS) - an older obsolete measure of a computer's speed and power. Measures roughly the number of machine instructions that a computer can execute - Floating Point Operations Per Second (FLOPS) - Is a measure of computer performance, useful in fields of scientific computations that require floating-point calculations. More accurate measure.

Microprocessors are also compared based on

How many transistors they contain

Data stores - Cloud

Increasingly now people use "cloud" as a data store, more an 'attic' to store the too-much-stuff to fit on computer disk, or stuff to be shared (so you can access it anywhere with anything, or so it is shareable with friends/colleagues). Many handheld devices use cloud storage without it necessarily being evident to users (unless network or cloud fails).

Cache contains a small piece of

Main memory

What types of devices are most prone to failure?

Mechanical Drives

What is a memory that May not require electrical power:

Non-volatile memory

Cache hit ratio formula =

Number of memory accesses of content in cache/Total number of memory accesses

CPU is called central because

Old mainframes had several processors, but only one was central

What is a computer?

Refers to an electronic device for storing and processing data, typically in binary form, according to instructions given to it in a variable program

Retains data as long as power is supplied?

SRAM

What is cache?

Small amount of high-speed memory between CPU & bus May be multi-staged Volatile

Not all memories are the same:

Smaller access time ⇒ higher co$t per bit Bigger capacity ⇒ smaller co$t per bit Higher capacity ⇒ higher access time

What is memory?

Stores bit patterns (instructions, data), Organized as flat, linear sequence of Bytes, Is byte addressable (usually), May generate traps for error conditions. Place to hold a value (data or instruction) while it is worked on or until it is needed to be worked on

Which part of a computer is responsible for operating/coordinating all of its components?

The Operating System

Computers may have more than one bus T o F?

There may be separate buses for specialized functions within the device. True

Bus is controlled by dedicated hardware T o F

True - (in a PC, on the motherboard) whose task is to create and operate the address space (not all addresses are memory addresses: some are addresses of I/O devices in a memory-mapped model [which is pretty much everything today]).

Computers have at least one bus T or F

True, often >1

Each place in memory has an address which

Uniquely identifies it

The CPU interacts with the bus ...

almost all the time ( actually with memory on the bus) .. the only connection between CPU and memory is via the bus.

Magnetic HDDs still popular,

but being supplanted in laptops with SSDs: much lower power (hence also less heat), all electronic; still need backing up against failure.

Some memory is non-volatile, holds its content in the absence of power

commonly seen in USB memory sticks, or SD cards, and increasingly in Solid-State Drives (SSDs)

Networks now make it possible to

communicate digital data from anywhere

Other popular data stores include:

external devices like SD cards, USB sticks. Advantages of SSD but easily portable and still quite cheap per bit

Memory comes in several forms:

main" memory (sometimes called RAM in computers), cache memory (multiple levels in some systems, separate I/D).

CPU executes instructions retrieved from

memory

I/O Capabilities:

network, user input, user output,

Clouds introduce security issues of their own

potential issues of ownership of content (in some cases), legal issues (your data may be stored on a computer in another country, hence subject to laws that apply there but not here). And, a lot of "administrators" potentially have access to / control of it.

Data store:

special case of non-volatile memory

CPU's do very simple things

very fast and execute instructions retrieved from memory


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