DMA is a problem with multiple cpu’s.
To improve system performance in a computer
o Multiple cpus
o Faster clock speed
o Wider instruction and data path
o Faster disc access
o More and faster memory
Multiprocessing increases parallel processing
o 2 types are Tightly processing:Each system has its own cpu, each sys known as a node.
o Loosely coupled systems: extends multitasking and program execution
A masterslave processing is a master cpu that controls the system its simple but if it fails, the
whole system does.
The OSI model was created by ISO.
OSI consists of 7 layers
Ring network topology is bus is closed no ends.Undirectional and pnt to pnt. 2mb-16mb/sec
Star is a central node does most of the processing remote nodes are connected point to point
with it. Has 2 undirectional links. 1gb/s
Loop is similar to ring, nodes directly in communication path.
Hierarchical is a tree like structure
Web is everything connected to everything else.
MAC are characteristics of the channels , data , rate ,voltage lvls etc. detects errors has Ethernet
and token ring.
Token ring MAC protocol token seized by changing a bit to indictate start of frame rather then
Hub is central element of the star layout.
Point to point connectivity has 1. Phone lines 2. Cables 3. Wireless 4. Fiber optics.
Gateway communicates different networks
Bridges communicate similar networks
Peripherals are classified as Input, output, and Storage.(not the cpu,memory etc).
Access time is the time it takes to locate data and read it.
Throughput is the amount of data moved per second(always kb/s)
Primary memory is immediate access by the cpu(cached,conventenial)
Expanded storage(ram) a buffer between the cache and conventenial
The track is the circle of the magnetic disk
Cylinder is the small track on all platters
Sector is the pie shaped part of the platter
A capacity of a harddisk can be from 5mb to 1+ tb The Winchester disk cannot contain dust particles, invented by IBM
Platter is the round surface the disk containing a magnetic coating
Track is the the circle on the disk surface in which data are contained
Head assembly is a mechanical unit holding the heads and arms
The drive motor rotates all the platters
Block is the smallest unit of data that can be written or read.
Seek time is the time for the head to move to the correct track
Latency time is the time it takes for the correct block to reach the head
Transfer rate is same as throughput
Avg.Latency time ½*1/Rotational speed
With multiblock transfers, sometimes sectors cannot be read or written consequetively , this
results in lost performance. It must undergo a full revolution to the next sector. The solution?
Interleaving basically skips one or more blocks in its numbering
Logical mapping is the way information is perceived to be stored
Physical mapping is the way information is actually stored
Removable hard discs are also called disk packs
RAID(Redundant Array of Inexpensive Discs) This is mostly used on servers
Level 0 is Data Striping, no redundancy, does not have fault tolerance but improves
Level 1 is Data mirroring(shadowing),one drive fails another can replace it, has fault tolerance
Level 3 same as lvl 0, reserves 1 disk for error correction data, some lvl of fault tolerance
Level 5 has excellent performance and fault tolerance, data striping at the byte lvl
Fault tolerance is the ability for a computer system to respond calmly to hardware/software
Data mirroring is if one disk fails, there is another one it can switch to without the loss of data
Data striping is spreading data over multiple disks
Optical storage uses light generated lasers to record and retrieve info
CD-ROM(Compact disk read only memory) capacity of 550mb
CD-ROM speed is CLV, Magnetic disk is CAV
Harddrive magnetic, CD optical
Has about 270,000 blocks
In optical storage laser strikes land:light reflected into detector. Laser strikes a pit:light scatters
Resolution is pixels on screen, when a computer boots up it goes to VGA(480x640) first, then
Pixel is a single point in a picture element
With 8 bits per pixel a monitor can display 256 shades of grey colors
Raster is the diagonal dimension of the screen
Slide 82 very important!!!
Pixel color is determined by 3 colors RGB(4 bits per color 16 x 16 x 16 = 4096 colors) CRT has 3 guns shooting to the screen for each color(electron guns)
Contains vacuum tube
The color transformation table(with 16 bits) the table can only represent 64,000 colors
The 24 bit colors cannot be displayed on this table.
A raster scan is scanning and displaying each pixel
Interlacing scans the odd lines first, then goes back to scan the even ones
The I/0 device connected to the cpu through the I/O module
Types of I/O. Programmed I/O, Interrupt driven,DMA.
The I/O module recognized messages from device and accepts command from the cpu. Has a
buffer and controls the device
I/O devices run completely from the cpu control
I/O module contains Device controller, and Disk controller.
I/O device is keyboard,mouse,printer, etc all the externals devices.
I/O configurations through data,address,control.
Programmed I/O(First Type of I/O) Connected to a pair of I/O registers in cpu bus. Transfers one
word at a time. Very slow.
Polling is programmed I/O where the device is status is checked to determine if an I/O operation
Interrupt driven(Second type of I/O) Signal that causes the cpu to alter its normal flow of
Register saves in the stack or PCB
External events interrupt occurs when an external device is inputed into the computer. This