AIT 542
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
