USB
The most universal and popular port you can meet in your laptop is USB. First version - USB 1.0 - was developed in November 1995. That was the time first USB ports started to appear in laptops and desktop computers.
USB Speed Versions
The USB 1.0 standard defined maximal data transfer at 1.5Mb/s (0.19MB/s) level. During the years USB was gaining popularity and new versions were released - USB 1.1 in September 1998 with 12Mb/s (1.5MB/s) bandwidth and USB 2.0 in April 2000 that could transfer data with very high 480Mb/s (60MB/s) speed. The popular names for these three standards are Low Speed (USB 1.0), Full Speed (USB 1.1) and Hi Speed USB for USB 2.0.
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To indicate which version of USB interface does the device support two types of USB logo are used. Devices that support USB 1.0 or USB 1.1 can use Basic-Speed version of logo. Hi-Speed logo version is reserved for USB 2.0 compliant products. |
| Basic-Speed Logo | Hi-Speed Logo |
Today you can hardly find any computer without at least one USB 1.1 port, even if you are going to buy really old refurbished laptop. Most laptops manufactured after April 2000 support USB 2.0 and have at least two, often more, USB port connectors.
To find out which version of USB does your laptop support you can use this tool: Intel USB System Check
USB Hub
You have to note, that port and port connector are not the same thing. When we talk about port, we think about USB port logic and electrical driver that each has 480Mb/s bandwidth.
USB standard allows connecting up to 127 devices to one USB port. To do this, you need special equipment - hub - that splits one port to more port connectors. When you connect devices through hub, port bandwidth is shared between them.
When you meet laptop with 6 USB port connectors, most probably few of them are just hub-split signal from one USB port driver. In most cases though, it wouldn't probably matter for you.
External Powered USB Hub
USB devices can be powered from USB port. Each connector you meet in laptop is so-called "type A" flat 4 pins connector as you can see at the photo on the top of the page. Two external pins are 5V power supply. Internal pins are used for serial data transfer. Each USB port driver can drive up to 0.5A current to connected devices. If you want to extend USB port with hub and total amount of current your USB devices need exceed 0.5A, you have to buy external powered hub. Powered hub doesn't take current from USB port it splits, but from external power supply, allowing each device connected to it draw 0.5A current for itself.
Hot-Swapping
USB devices can be hot plugged and unplugged without turning the computer off. This is so-called "hot-swapping" capability. USB protocol standards are designed to support also "plug and play", which means, that after you connect your device to the computer, operating system (if it supports "plug and play") automatically detects and install the device making it ready to use almost immediately.
USB Features List
Let's look at the summary of USB features:
- 4 pins type A connector on the computer side (bottom-page diagram).
- 4 pins type B connector on the device side (bottom-page diagram).
- Three USB standards USB 1.0 (1.5Mb/s), USB 1.1 (12Mb/s) and USB 2.0 (480Mb/s).
- Up to 127 devices working together on the same bus.
- Powering from USB port, up to 0.5A.
- Powered and unpowered host devices to extend amount of USB port connectors.
- Up to 5m long cables.
- "Hot-swapping" and "plug & play" capabilities.
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Type A |
| Type B |
If you would like to know more look at: www.usb.org.
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