Computers use different buses to communicate with other devices. These other devices include printers, disk drives, scanners, modems, and scientific instruments.
Here is a brief summary of the more important buses.
| Name | Speed, megabytes/sec | Type | # Devices | Comments |
| Parallel port, a.k.a. Centronics parallel | 0.115 | parallel asynchronous handshaking | 1:1 | One of the first PC buses, it is most widely used for printers. |
| ECP/EPP parallel port | 3 | 8-bit parallel asynchronous handshaking | 1:1 | Improved version of the printer bus, same connector, backward compatible, it is most widely used for printers. |
| RS-232C, a.k.a. serial port | up to 0.0115 | serial asynchronous, Lawrence Welk | 1:1 | Most commonly used for external modems. |
| IEEE-488, a.k.a. GPIB, HPIB | 0.3 | 8-bit parallel, asynchronous, handshaking | 15 | Mainly used for connecting computers to scientific instruments. |
| IDE, a.k.a. ATA | 3.3 - 16.7, depending on version | 16-bit synchronous | 1:2 | Connects motherboard to hard drives |
| SCSI-1 | 5 | 8-bit parallel asynchronous handshaking | 7 | Used to connect motherboard to hard drives, scanners, high speed peripherals. |
| SCSI-2 | 10 | " | " | Just a faster version of above. |
| Fast, wide, Ultra 2, Ultra 3, etc., SCSI | Up to 80, depending on which combination of the terms at left | Wide means 15 bits. | " | Faster, faster again. |
| Serial ATA, a.k.a. SATA | up to 150 | serial synchronous | 1 per cable, typically two in a computer | Fastest connection to hard drives, also has the advantage of smaller cables, which eases air flow problems. |
| SATAII | up to 300 | serial synchronous | 1 per cable, typically two in a computer | Faster version of SATA due to hit the market in 2005.. |
|
USB1.0/1.1 (universal serial bus) |
1.5 | serial synchronous | 127 |
The new standard for connecting slow to medium speed devices to computers. This has quickly become the most popular choice for connecting printers, scanners, modems, digital (still) cameras. There are some external hard drives for USB, but the bus is too slow for good performance. This bus is too slow for digital video. It allows "hot connecting", plugging and unplugging the device with the computer running. Maximum distance is 5 meters. |
| USB 2.0 | 48 | Serial synchronous | 127 | Souped up version of USB 1.0. Has replaced USB 1.0/1.1 almost completely. |
| IEEE-1394, a.k.a. Firewire | 40 | Serial synchronous |
1 to :many Up to 63 nodes with 16 devices each. |
External hard drives, digital video. Most digital camcorders have firewire interfaces. You can get external removable hard drives that plug into firewire. Hot connecting. |
| IEEE-1394b, a.k.a. Firewire2 | 80 | Serial synchronous | 1:to many Up to 63 nodes with 16 devices each. |
External hard drives, digital video. Most digital camcorders have firewire interfaces. You can get external removable hard drives that plug into firewire. Hot connecting. |
| Bluetooth | 11.5 | Wireless | Several | Short range (10 m) wireless. This is targeted at communication between PC, printer, cell phone, PDA, etc. |
| Ethernet, Thinnet | 1 | Serial, asynchronous | 4 billion or more, depending on protocol (IPv6 increases this by a factor of 65536) | The first ethernet, coaxial cable. |
| 10-baseT | 1 | Serial, asynchronous | " | Same as above, but runs over twisted pair. |
| 100-baseT | 10 | " | " | Same as above, but 10 times faster |
| Gigabit ethernet, a.k.a. Gig-E | 100 | " | " | Same as above, but 10 times faster still. |
| FDDI | 10 and up | " | " | Fiber optic alternative to ethernet. |
| ATM | 10 and up | " | " | Another fiber protocol, but provides better support for streaming media where arrival time is important. |
| 802.11B | 1.1 | " | " | Most common wireless, 11 Mbps, 2.4 GHz |
| 802.11G | 5.4 | " | " | Upcoming standard . Faster. 2.4 GHz. Backward compatible with 802.11B, BUT one 802.11B device will slow the whole group to 802.11B speeds. |
| 802.11A | 5.4 | " | " | Same speed, but more channels, different band. 5 GHz. |
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