bus,wire,connection
there are three different types of interconnects in modern computer systems:chip to chip,board to board,and system to systme;
1 hypertransport is primarily an interconnect which connects chips to chips.
2 examples of board-to-board interconnects are PCI,PCI-X,PCI express,and AGP;
3 examples of system to system interconnects are ethernet,fiber channel,infiniBand,firewire,as well as Peripheral connections like SCSI,serial ATA.
| feature | usb 1.1 | usb 2.0 | firewire 400 | firewire 800 |
| data transfer rate | 12 MB/s | 480 MB/s | 400 MB/s | 800 MB/s |
| number of deivces | 127 | 127 | 63 | 63 |
| cables | 4 wires | 4 wires | 6 wires | 8 wires |
| plug and play | yes | yes | yes | yes |
| hot-pluggable | yes | yes | yes | yes |
| isochronous devices | yes | yes | yes | yes |
| bus power | yes | yes | yes | yes |
| bus termination | no | no | no | no |
| bus typle | seral | seral | seral | seral |
| net work | host-based | host-based | peer-to-peer | peer-to-peer |
| network topology | hub | hub | daisy chain | daisy chain |
USB Features
The computer acts as the host;
Up to 127 devices can be connected to the host,either directly or by usb hubs;
The device connected to a USB port rely on the USB cable to carry power and data.
Individual USB cables can run as long as 5 meters;
With hubs,deivces can be up to 30 meters(six cables'worth)away from the host;
USB has a maximum data rate of 480 megabits per second(usb 2.0);
A USB cable has two wires for power,+5 Volt(red and ground(brown),and a twisted pair of wires(yellow and blue)to carry the data.The cable is dhielded;
On the power wires,the computer can supply up to 500 milliamps of power at 5 Volt.
Low-power devices(such as mice) can draw their power directly from the bus.High-power devices(such as printers) have their own power supplies and draw minimal power from the bus.Hubs can have their own power supplies to provide power to devices connected to the hub.
USB devices are hot-swappable,meaning you can plug them into the bus and unplug them any time.
Many USB devices can be put to sleep by the host computer when the computer enters a power-saving mode.
if you have lots of un-powered like mice and cameras,you prbably need a powered hub,so that the devices do not overload the computer's supply.
Firewire,with the official name of IEEE 1394,is a serial bus to connect high speed digital devices,especially audio and video equipment,so they can easyly and quickly transfer information.With a firewire bus,you and connect up to 63 devices.the latest version of firewire 800 achieves speeds up to 800 MB/s.Both windows OS and Mac OS support firewwire
usb 2.0 is host-based,meaning that devices must be connect to a computer in order to communicate.Firewire is peer-to-peer,meaning that two firewire cameras can talk to each other without going through a computer.
serial port:provide a standard connector and protocol to let you attach devices,such as modems,to your computer.
Parallel port:if you have a printer connecte to your computer,there is a good chance that it uses the parallel port.while usb is becoming increasingly popular,the parallel port is still a commonly used inferface for printers.
when you plug a digital camera into your computer,you're probably using a universal serial bus port.Your USB port is good at carrying the data and electricity required for samll electronic devices.But that bus isn't big enough to support a whole computer,a server or lots of devices simultaneously.For that,you'd need something more like SCSI.SCSI uses a controller to send and receive data and power to SCSI-enabled devices,like hard drives and printers.
Seria ATA is a newly defined bus standard primarily for transferring data to/from a hard disk.It is the successor to the advanced technology attachement standard(ATA,also known as IDE).To distinguish it from serial ATA,the older ATA standard was renamed parallel ATA.
as the name suggests.serial ATA uses serial link for data transferring.It is a point-to-point connection,meaning that SATA drops the master/slave shared bus structure of PATA,giving each device a dedicated cable and dedicated bandwidth.
to achieve longer link and faster data rate,SATA uses LVDS(low voltage digital signal)differential signals to reduce the noise interferences.It also uses 8B/10B encoding at the physical layer.8B/10B is a technology that converts an 8-bit data byte into a 10-bit package to achieve DC balance,and provide enough state changes to allow clock recovery.
the SATA standard defines a data cable using 7 wires and 8 mm wide wafer connectors on each ind.Of the 7wires,a pair is for data transmission,a pair is for data receiving,and the remaining 3 are for grounding.The reduction in conductors makes SATA connectors and cables much narrower than those of PATA,thus making them more convenient to route within tight spaces.The internal SATA cables can be up to 1 meter long.
The SATA standard also specifies a power connector.It is a wafer-based 15-pin connector.It can supply three different voltages-3.3,5,12 Volt.Each voltage is supplied by three pins ganged together.
| eSATA | PATA | fire wire 1394b | usb 2.0 | |
| actual speed | 2.4 GB/s | 1,064 MB/s | 786 MB/s | -375 MB/s |
| max.cable length | e meters | 46 centimeters | 4.5 meters | 5 meters |
| power cable | Y | N | Y | Y |
| devices/channel | 1 | 2 | 63 | 127 |
in the early days of computing,a vast amount of data moved over serial connections.Serial connections were slow,so manufactureers began using parallel connections.It turns out that parallel connections have their own problems as speeds get higher and higher-Interference from nearby wires and signal degradation thanslate into noise,which limits the speed of the connection.So now the pendulum is swinging back toward serial connections.
PCI peripheral component has been an integral part of a computer's architecture that provides a versatkle,functional way to connect sound,video and network cards to a motherboard;
The PCI bus is for communicating with I/O devices,such as networks,audio,and video.It provides direct access to main memory for connected devices,but connects to the system bus via a bridge inside the chipset.
Storage is an important part of a computer.Most personal computers have one or more of the following storage devices:floppy drive,hard drive,and CD-ROM drive.Usually,these devices are connected to the computer through an integrate drive electronics interface;
IDE was created as a way to standardize the use of hard drives in computers.The basic concept behind IDE is that the hard drive and the controller should be combined.The controller is a small circuit board with chips that provide guidance as to exactly how the hard drive stores and accesses data.Most controllers also include some memory that acts as a buffer to enhance hard drive performance.
IDE devices use a ribbon cable to connect to each other.Ribbon cables have all of the wires laid flat next to each other instead of bunched or wrapped together in a bundle.IDE ribbon cables have either 40 or 80 wires.There is a connector at each end of the cable and another one about two-thirds of the distance from the motherboard connector.this cable cannot exceed 46cm in total length to maintain signal integrity.The three connectors are typically different colors and attach to specific items;
the blue connector attaches to the motherboard.
the black connector attaches to the primary(master)drive;
the gray connector attaches to the secondary(slave)drive;
a single IDE interface can support tow devices.Because the controller is integrated with the drive,there is no overall controller to decide withich device is currently communcating with the computer.
befor AGP,the standard method of delivery was the Peripheral Component Interconnect(PCI)bus.AGP is based on the design of the PCI bus.But unlike a bus,it provides a dedicated point-to-point connection from the graphics card to the CPU.