Peripheral Component Interconnect (PCI) Conventional PCI, often shortened to PCI, is a local computer bus for attaching hardware devices in a computer. PCI stands for Peripheral Component Interconnect and is part of the PCI Local Bus standard. The PCI bus supports the functions found on a processor bus but in a standardized format that is independent of any particular processor's native bus. Devices connected to the PCI bus appear to a bus master to be connected directly to its own bus and are assigned addresses in the processor's address space. it is a parallel bus, synchronous to a single bus clock. Bus Example: Pentium II (1) Front side bus - connects CPU to memory and other devices (usually more than one of these) (2) Back side bus - connects CPU to level 2 (L2) cache. (a) Back side bus is much faster (b) Runs as the CPU clock speed (or some fraction of it) (c) Individual back-side buses help eliminate a bottleneck in multiple CPU systems Bus Example: PCI PCI developed around 1990 by Intel to address increasing needs for more bus bandwidth they put the rights to it into the public domain to encourage vendors to support it processor independent 256 Byte local device memory accessible to other devices for configuration (i.e., allows plug-n-play installation) synchronous address and data lines are multiplexed to keep pin count down allows 32 or 64 bit operation versions: PCI 1.0-33 MHz (32 bits) PCI 2.0-66 MHz or 133 MHz (64 or 32 bits) PCI-X (3.0) - first ones just coming out PCI Basic Operation transactions take 3 cycles: cycle 1 - master puts address on lines cycle 2 - master removes address and bus is (if reading) turned around in preparation for data cycle 3 - data is put on bus if slave cannot respond on cycle 3, it inserts wait states block transfer of unlimited sizes are allowed
PCI Bus Arbitration centralized (separate chip or part of another bus control chip) each device has dedicated two lines to arbiter: bus request bus grant device asserts the request and waits until the grant line is asserted. arbitration algorithm not specified by PCI specification bus granted for one transaction (which is more than one cycle) bus master can keep the bus for a subsequent transaction if there is no other bus request if the bus arbiter ever negates the bus grant line, the bus master must relinquish it on the next cycle Universal Serial Bus (USB) The Universal Serial Bus (USB) is technology that allows a person to connect an electronic device to a computer. It is a fast serial bus. It is mostly used on personal computers. USB is also used on other devices, like the PlayStation 3, PlayStation 4, the Xbox 360, and others. USB connects different devices using a standard interface. Most people use USB for computer mice, keyboards, scanners, printers, digital cameras, and USB flash drives. There are over six billion USB devices around the world. The standard was made to improve plug and play devices. This means that a device can be plugged into a free socket, and simply work. The computer will notice the device. The computer sometimes installs special software so that the device can directly be used. The device can be removed after it stops being used. This technology is called "hot swapping". "Hot swapping" means it can be plugged and unplugged while the power is on. The computer does not need to be turned off for people to change the devices. USB can also provide a small amount of power to the attached device through the USB cord. Devices that only need a little power can get it from the bus, and do not need a separate electric power plug. That allows gadgets like USB battery chargers, lights, and fans. As of 2015, USB has replaced several older standards. Those include the parallel port, serial port and SCSI. Some special purposes still need those old connection methods. for low-speed I/O devices keyboard, mouse, scanners, printers, cameras, etc. simplify addition/configuration of low-speed devices same cable/connector installable while computer running (and without reboot) Bandwidth: 1.5 MB/sec
root USB hub plugs into main (e.g., PCI) bus cables plug into hub and can go to devices or expansion hubs cable has 4 wires: 2 data, one power, one ground new device generates and interrupt USB interrupt handler finds out what this new device is and how much bandwidth it needs Working A USB system has an asymmetric design. It is made of a host, several downstream USB ports, and multiple peripheral devices connected in a star topology. Additional USB hubs may be included in the tiers, allowing branching into a tree structure with up to five tier levels. A USB host can have multiple host controllers. Each host controller provides one or more USB ports. Up to 127 devices, including the hub devices may be connected to a single host controller. USB devices are linked in series through hubs. There is always one hub known as the root hub. The root hub is built into to the host controller. There are special hubs, called "sharing hubs". These allow multiple computers to access the same peripheral devices. They work by switching the access between PCs, either manually or automatically. They are popular in small-office environments. In network terms, they converge rather than diverge branches. A physical USB device can have several logical sub-devices that are referred to as device functions. A single device may provide several functions, for example, a webcam (video device function) with a built-in microphone (audio device function).
Various buses placed in a computer system (just for the sake of knowledge)
Small Computer System Interface (SCSI) Small Computer System Interface (SCSI) is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, electrical and optical interfaces. SCSI is most commonly used for hard disk drives and tape drives, but it can connect a wide range of other devices, including scanners and CD drives, although not all controllers can handle all devices. The SCSI standard defines command sets for specific peripheral device types; the presence of "unknown" as one of these types means that in theory it can be used as an interface to almost any device, but the standard is highly pragmatic and addressed toward commercial requirements. Common SCSI components There are several components used in SCSI storage systems: Initiator. An initiator issues requests for service by the SCSI device and receives responses. Initiators come in a variety of forms and may be integrated into a server s system board or exist within a host bus adapter. ISCSI connectivity typically uses a software-based initiator. Target. A SCSI target is typically a physical storage device (although software-based SCSI targets also exist). The target can be a hard disk or an entire storage array. It is also possible for non-storage hardware to function as a SCSI target. Although rare today, it was once common for optical scanners to be attached to computers through the SCSI bus and to act as SCSI targets. Service delivery subsystem. The mechanism that allows communication to occur between the initiator and the target; it usually takes the form of cabling. Expander. Only used with serial-attached SCSI (SAS); allows multiple SAS devices to share a single initiator port. Serial Attached SCSI (SAS) Serial Attached SCSI (SAS) is a point-to-point serial protocol that moves data to and from computer storage devices such as hard drives and tape drives. SAS replaces the older Parallel SCSI (Small Computer System Interface, usually pronounced "skuzzy") bus technology that first appeared in the mid-1980s. SAS, like its predecessor, uses the standard SCSI command set. SAS offers backward compatibility with SATA, versions 2 and later. This allows for SATA drives to be connected to SAS backplanes. The reverse, connecting SAS drives to SATA backplanes, is not possible. The T10 technical committee of the International Committee for Information Technology Standards (INCITS) develops and maintains the SAS protocol; the SCSI Trade Association (SCSITA) promotes the technology. A typical Serial Attached SCSI system consists of the following basic components: An initiator: a device that originates device-service and task-management requests for processing by a target device and receives responses for the same requests from other target devices. Initiators may be provided as an on-board component on the motherboard (as is the case with many server-oriented motherboards) or as an add-on host bus adapter. A target: a device containing logical units and target ports that receives device service and task management requests for processing and sends responses for the same requests to initiator devices. A target device could be a hard disk or a disk array system. A service delivery subsystem: the part of an I/O system that transmits information between an initiator and a target. Typically cables connecting an initiator and target with or without expanders and backplanes constitute a service delivery subsystem. Expanders: devices that form part of a service delivery subsystem and facilitate communication between SAS devices. Expanders facilitate the connection of multiple SAS End devices to a single initiator port.
Serial AT Attachment (SATA) Serial ATA (SATA, abbreviated from Serial AT Attachment) is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives. Serial ATA succeeded the older Parallel ATA (PATA) standard,[a] offering several advantages over the older interface: reduced cable size and cost (seven conductors instead of 40 or 80), native hot swapping, faster data transfer through higher signaling rates, and more efficient transfer through an (optional) I/O queuing protocol. Prior to SATA's introduction in 2003, the PATA was simply known as ATA. The AT Attachment (ATA) name originated after the 1984 release of the IBM Personal Computer AT, more commonly known as the IBM AT. The IBM AT was the first mass-produced computer where the hard disk was key to the system's performance. The IBM AT s controller interface became a de facto industry interface for the inclusion of hard disks. AT was IBM s abbreviation for Advanced Technology ; thus, many companies and organizations indicate SATA is an abbreviation of Serial Advance Technology Attachment ; however, the ATA specifications simply use the name "AT Attachment", to avoid possible trademark issues with IBM. SATA host adapters and devices communicate via a high-speed serial cable over two pairs of conductors. In contrast, parallel ATA (the redesignation for the legacy ATA specifications) used a 16-bit wide data bus with many additional support and control signals, all operating at much lower frequency. To ensure backward compatibility with legacy ATA software and applications, SATA uses the same basic ATA and ATAPI command sets as legacy ATA devices. SATA has replaced parallel ATA in consumer desktop and laptop computers; SATA's market share in the desktop PC market was 99% in 2008. PATA has mostly been replaced by SATA for any use; with PATA in declining use in industrial and embedded applications that use CompactFlash (CF) storage, which was designed around the legacy PATA standard. A 2008 standard, CFast to replace CompactFlash is based on SATA. Serial ATA industry compatibility specifications originate from the Serial ATA International Organization (SATA- IO). The SATA-IO group collaboratively creates, reviews, ratifies, and publishes the interoperability specifications, the test cases and plugfests. As with many other industry compatibility standards, the SATA content ownership is transferred to other industry bodies: primarily the INCITS T13 subcommittee ATA, the INCITS T10 subcommittee (SCSI), a subgroup of T10 responsible for Serial Attached SCSI (SAS). The remainder of this article will try to use the terminology and specifications of SATA-IO. PCI Express (Peripheral Component Interconnect Express) PCI Express (Peripheral Component Interconnect Express), officially abbreviated as PCIe, is a high-speed serial computer expansion bus standard, designed to replace the older PCI, PCI-X, and AGP bus standards. PCIe has numerous improvements over the older standards, including higher maximum system bus throughput, lower I/O pin count and smaller physical footprint, better performance scaling for bus devices, a more detailed error detection and reporting mechanism (Advanced Error Reporting, AER), and native hot-plug functionality. More recent revisions of the PCIe standard provide hardware support for I/O virtualization. The PCI Express electrical interface is also used in a variety of other standards, most notably in Express Card as a laptop expansion card interface, and in SATA Express as a computer storage interface.
Format specifications are maintained and developed by the PCI-SIG (PCI Special Interest Group), a group of more than 900 companies that also maintain the conventional PCI specifications. PCIe 3.0 is the latest standard for expansion cards that are in production and available on mainstream personal computers. Year created 2004; 12 years ago Created by Intel Dell HP IBM Supersedes AGP PCI PCI-X Width in bits 1 32 Number of devices One device each on each endpoint of each connection. PCI Express switches can create multiple endpoints out of one endpoint to allow sharing one endpoint with multiple devices. Speed For single-lane ( 1) and 16-lane ( 16) links, in each direction: v. 1.x (2.5 GT/s): o 250 MB/s ( 1) o 4 GB/s ( 16) v. 2.x (5 GT/s): o 500 MB/s ( 1) o 8 GB/s ( 16) v. 3.x (8 GT/s): o 985 MB/s ( 1) o 15.75 GB/s ( 16) v. 4.0 (16 GT/s): o 1.969 GB/s ( 1) o 31.51 GB/s ( 16) Style Hotplugging interface External interface Serial Yes, if Express Card, Mobile PCI Express Module, XQD card or Thunderbolt Yes, with PCI Express External Cabling, such as Thunderbolt
FireWire IEEE 1394 is an interface standard for a serial bus for high-speed communications and isochronous real-time data transfer. It was developed in the late 1980s and early 1990s by Apple, which called it FireWire. The 1394 interface is also known by the brand i.link (Sony), and Lynx (Texas Instruments). The copper cable it uses in its most common implementation can be up to 4.5 meters (15 ft) long. Power is also carried over this cable allowing moderate-consumption devices to operate without a separate power supply. FireWire is also available in wireless, Cat 5, fiber optic, and coaxial versions. The 1394 interface is comparable to USB though USB requires a master controller and has greater market share. IEEE 1394 replaced parallel SCSI in many applications, because of lower implementation costs and a simplified, more adaptable cabling system. Type Serial Production history Designer Apple Inc. (1394a/b), IEEE P1394 Working Group Designed 1994; 22 years ago Manufacturer Various Produced 1994 present General specifications Length 4.5 meters maximum Width 1 Hot Yes pluggable Daisy chain Yes, up to 63 devices External Yes Pins 4, 6, 9
Electrical Max. voltage 30 V Max. current 1.5 A Data Data signal Yes Bitrate 400 3200 M bit/s (50 400 MB/s)