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List of interface bit rates: Difference between revisions

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This is a list of device bit rates, or physical layer information rates, net bit rates, useful bit rates, peak bit ratesordigital bandwidth capacity, at which digital interfaces of computer peripheral equipment and network devices can communicate over various kinds of buses and networks.

The distinction can be arbitrary between a bus, (which is inside a box and usually relies on many parallel wires), and a communications network cable, (which is external, between boxes and rarely relies on more than four wires). Many device interfaces or protocols (e.g., SATA, USB, SCSI, PCI and a few variants of Ethernet) are used both inside many-device boxes, such as a PC, and one-device-boxes, such as a hard drive enclosure. Accordingly, this page lists both the internal ribbon and external communications cable standards together in one sortable table.

Factors limiting actual performance, criteria for real decisions

Most of the listed rates are theoretical maximum throughput measures; in practice, the actual effective throughput is almost inevitably lower in proportion to the load from other devices (network/bus contention), interframe gap, and other overheadindata link layer protocols etc. The maximum goodput (for example, the file transfer rate) may be even lower due to higher layer protocol overhead and data packet retransmissions caused by line noiseorinterference such as crosstalk, or lost packets in congested intermediate network nodes. All protocols lose something, and the more robust ones that deal resiliently with very many failure situations tend to lose more maximum throughput to get higher total long term rates.

Device interfaces where one bus transfers data via another will be limited to the throughput of the slowest interface, at best. For instance, SATA 6G controllers on one PCIe 5G channel will be limited to the 5G rate and have to employ more channels to get around this problem. Early implementations of new protocols very often have this kind of problem. The physical phenomena on which the device relies (such as spinning platters in a hard drive) will also impose limits; for instance, no spinning platter shipping in 2009 saturates SATA II (3 Gbit/s), so moving from this 3 Gbit/s interface to USB3 at 4.8 Gbit/s for one spinning drive will result in no increase in realized transfer rate.

Contention in a wireless or noisy spectrum, where the physical medium is entirely out of the control of those who specify the protocol, requires measures that also use up throughput. Wireless devices, BPL, and modems may produce a higher line rateorgross bit rate, due to error-correcting codes and other physical layer overhead. It is extremely common for throughput to be far less than half of theoretical maximum, though the more recent technologies (notably BPL) employ preemptive spectrum analysis to avoid this and so have much more potential to reach actual gigabit rates in practice than prior modems.

Another factor reducing throughput is deliberate policy decisions made by Internet service providers that are made for contractual, risk management, aggregation saturation, or marketing reasons. Examples are rate limiting, bandwidth throttling, and the assignment of IP addresses to groups. These practices tend to minimize the throughput available to every user, but maximize the number of users that can be supported on one backbone.

Furthermore, chips are often not available in order to implement the fastest rates. AMD, for instance, does not support the 32-bit HyperTransport interface on any CPU it has shipped as of the end of 2009. Additionally, WiMax service providers in the US typically support only up to 4 Mbit/s as of the end of 2009.

Choosing service providers or interfaces based on theoretical maxima is unwise, especially for commercial needs. A good example is large scale data centers, which should be more concerned with price per port to support the interface, wattage and heat considerations, and total cost of the solution. Because some protocols such as SCSI and Ethernet now operate many orders of magnitude faster than when originally deployed, scalability of the interface is one major factor, as it prevents costly shifts to technologies that are not backward compatible. Underscoring this is the fact that these shifts often happen involuntarily or by surprise, especially when a vendor abandons support for a proprietary system.

Conventions

By convention, bus and network data rates are denoted either in bit/s (bits per second) or byte/s (bytes per second). In general, parallel interfaces are quoted in byte/s and serialinbit/s. The more commonly used is shown below in bold type.

On devices like modems, bytes may be more than 8 bits long because they may be individually padded out with additional start and stop bits; the figures below will reflect this. Where channels use line codes (such as Ethernet, Serial ATA and PCI Express), quoted rates are for the decoded signal.

The figures below are simplex data rates, which may conflict with the duplex rates vendors sometimes use in promotional materials. Where two values are listed, the first value is the downstream rate and the second value is the upstream rate.

All quoted figures are in metric decimal units, where:

• 1 byte (B) = 8 bit
• 1 kbit/s = 1,000 bit/s
• 1 Mbit/s = 1,000,000 bit/s
• 1 Gbit/s = 1,000,000,000 bit/s
• 1 kB/s = 1,000 byte/s
• 1 MB/s = 1,000,000 byte/s
• 1 GB/s = 1,000,000,000 byte/s
• 1 TB/s = 1,000,000,000,000 byte/s

Note that these aren't the traditional binary prefixes for memory size. These decimal prefixes have long been established in data communications. This occurred before 1998 when IEC and other organizations introduced new binary prefixes and attempted to standardize their use across all computing applications.

Bandwidths

The figures below are grouped by network or bus type, then sorted within each group from lowest to highest bandwidth; gray shading indicates a lack of known implementations.

Time Signal StationtoRadio Clock

TTY/Teletypewriterortelecommunications device for the deaf (TDD)

Modems (Narrowband & Broadband)

The bytes column of this particular table shows a net data transfer rate after the protocol overhead has been removed.

(The other device tables show bit rate equivalents.)

Narrowband (POTS: 3.1 kHz channel)

Broadband (hundreds of kHz wide)

Mobile telephone interfaces

Wide area networks

Local area networks

Wireless networks

802.11 networks in infrastructure mode are half-duplex; all stations share the medium. In infrastructure or access point mode, all traffic has to pass through an Access Point (AP). Thus, two stations on the same access point that are communicating with each other must have each and every frame transmitted twice: from the sender to the access point, then from the access point to the receiver. This approximately halves the effective bandwidth.

802.11 networks in ad hoc mode are still half-duplex, but devices communicate directly rather than through an access point. In this mode all devices must be able to "see" each other, instead of only having to be able to "see" the access point.

Wireless personal area networks

Computer buses

Main buses

^z Uses 8b/10b encoding, meaning that 20% of each transfer is used by the interface instead of carrying data from between the hardware components at each end of the interface. For example, a single link PCIe 1.0 has a 2.5 Gbit/s transfer rate, yet its usable bandwidth is only 2 Gbit/s (250 MB/s).

^y Uses 128b/130b encoding, meaning that about 1.54% of each transfer is used by the interface instead of carrying data between the hardware components at each end of the interface. For example, a single link PCIe 3.0 interface has an 8 Gbit/s transfer rate, yet its usable bandwidth is only about 7.88 Gbit/s.

Portable

Storage

^a Uses 8b/10b encoding

Peripheral

MACtoPHY

PHYtoXPDR

Dynamic random access memory

The table below shows values for PC memory module types. These modules usually combine multiple chips on one circuit board. SIMM modules connect to the computer via an 8 bit or 32 bit wide interface. DIMM modules connect to the computer via a 64 bit wide interface. Some other computer architectures use different modules with a different bus width.

FPM, EDO, SDR, and RDRAM memories were not commonly installed in a dual-channel configuration. DDR and DDR2 memory are usually installed in single or dual-channel configuration. DDR3 memory are installed in single, dual, tri, and quad-channel configurations. Bit rates of multi-channel configuration are slightly increased.

Video RAM

RAM memory modules are also utilised by graphics processing units; however, video memory differs somewhat, particularly with lower power requirements, and is specialised to serve GPUs: for example, the introduction of GDDR3, which was fundamentally based on DDR2. Every video memory chip is directly connected to the GPU (point-to-point). The total GPU memory bus width varies with the number of memory chips and the number of lanes per chip. For example, GDDR5 specifies either 16 or 32 lanes per "device" (chip). Over the years, bus widths ranged from 64-bit to 512-bit.^[48] Because of this variability, graphics memory speeds are sometimes compared per pin. For direct comparison to the values for 64-bit modules shown above, video RAM is compared here in 64-lane lots, corresponding to two chips. In 2012, high-end GPUs use 8 or even 12 chips with 32 lanes each, for a total memory bus width of 256 or 384 bits. Combined with a transfer rate per pin of 5 GT/s or more, such cards can reach 240 GB/s or more.

Video RAM frequencies vary greatly. The values given below are examples for high-end cards.^[49] Since many cards have more than one pair of chips, the total bandwidth is correspondingly higher. For example, high-end cards often have eight chips, so that the total bandwidth is four times the value given below.

Digital audio

Digital video interconnects

Data rates given are from the video source (e.g., video card) to receiving device (e.g., monitor) only. Out of band and reverse signaling channels are not included.

^a Uses 8b/10b encoding for video data—effective data rate is 80% of the symbol rate

See also

• Bitrate (including Bitrates in multimedia)
• Comparison of mobile phone standards
• Comparison of wireless data standards
• List of Internet access technology bit rates in the Digital bandwidth article
• OFDM system comparison table
• Sneakernet
• Spectral efficiency comparison table
• Orders of magnitude (bit rate)

Notes