The USB standard has become the universal means of connection peripheral devices and equipment to the computer. Computers have either two or four USB port connectors. Each of these can support a large number of connections but to be able to attach more than two or four devices requires a multi-connection hub. There are many different types of hubs and this article seeks to explain some of the important considerations in selecting the best choice of hub for your system.
The USB bus system in computers was introduced in 1996 and has gone through a number of developments and enhancements. It started out as USB 1 which was very slow and had many bugs. Version 1.1 brought a higher bandwidth of 12 MBits/second. The latest version of 2.0 gives a bandwidth of 480MBits/second and is fully backward compatible with USB 1 and 1.1. Link to a table showing differences between USB speeds (http://www.usb-products.com/usb-speed.aspx)
Port Connections and Power
All USB standards support up to 127 connections (or devices) per computer port. It is unlikely that this would be achievable as the port can only supply 0.5 Amps maximum. Some devices consume a full 0.5 Amps, so are powered from a power adaptor from the mains supply.
Bandwidth Sharing
Generally, the bandwidth of the port (http://www.usb-products.com/usb-port.aspx) is shared between all the devices that are attached through a hub. This means that if you want to add two USB 2 devices with a USB 1.1 device, the bandwidth is shared between all three devices. However, there is an extra complication. Most hubs (http://www.usb-products.com/usb-hub.aspx) have a single chip controlling the bus. This means that the hub will work at the lowest bandwidth determined by the connected devices resulting in the USB 2 devices working at much lower transfer speeds. Nearly all USB hubs on the market today (passive and powered) operate like this.
Multiple Chip Hubs
The transaction translator (TT) is the name for the controlling chip that assigns bandwidth to each connected device. In hubs that have one TT all devices share the same bandwidth and operate at the speed of the slowest. In hubs with a TT per socket, each receives a share of the bandwidth, but this is not restricted to the slowest device. Examples of this type of hub is the Belkin Tetra hub (http://www.usb-products.com/Products/Hi-Speed-USB-2-0-4-Port-TetraHub.aspx) This has 4 ports each with its own TT.
What this means in reality is that a multiple TT hub will provide much higher bandwidth per port when several devices are connected from one hub.
Maximum Performance and choice of Where to connect a device If you are after maximum performance for each of your USB 2 devices, each device should be plugged into its own USB port in the computer. Additional plug in cards can provide a vast number of USB ports for most needs. However, this situation might be going too far except for the most demanding of situations. Although several USB devices might be connected at the same time it is unlikely that they will all be in use together.
A useful compromise is to plug small bandwidth devices together into a single hub. These would include: mice; keyboard; Speakers; little used devices.
For devices that require a high bandwidth and are used often, direct connection in to a USB port is the best option. Devices would include: Flash memory drives; external disks; Web cams; Other frequently used devices.
If you don't have sufficient ports then either more ports should be added with a plug-in card or a good quality hub with multiple transaction translators should be used. The devices placed on the hub are those that are used less often. Those devices placed directly on the port are used most often.
Link to a selection flow chart that helps in selecting a hub (http://www.usb-products.com/USB-Hub-Selection.aspx)
Access Considerations
What type of configuration and mix of port and hubs will depend on the number of devices that you wish to attach. Desktop computer cases usually have ports in the front of the case for easy access. These can be used for devices that are often plugged / unplugged and require the highest bandwidth. These are flash memory drives and portable external drives and MP3 players.
USB hubs tend to clutter up the area with cable connections and power lead. These naturally go out of sight if possible or behind the monitor. For mobile computers, a small compact hub can be obtained. These may have there own wind-in or tidy away cables.
Powered and Passive Hubs
Hubs may be restricted in their use without a power connection as passive hubs rely on the power of the USB bus. Powered hubs have a mains power adaptor to provide additional power for devices. These devices range in the power they require. It is possible to run a number of different devices all from a single passive hub running of a USB port as long as they have low power requirements. With only 0.5 Amps current it only takes one of the devices requiring the full power requirement for the hub to be overwhelmed. Nothing serious is going to happen though except that the single will degrade and many or all the devices will loose connection with the computer. To avoid this situation a powered hub should be used.
Nigel Stephens heads an online business at http://www.usb-products.com supplying computer hardware products. Nigel's emphasis is in providing useful information so that consumers can make more informed choices.
Are you captivated by the stunning Case Mods you've seen... Read More
We all know what it is like when that message... Read More
The USB standard has become the universal means of connection... Read More
Science-Fiction meets reality with this new video display technology.The Heliodisplay... Read More
IBM boasts a very large array of older and newer... Read More
Selecting motherboard is really simple. As name suggests "Motherboard" acts... Read More
DVD is an optical disc storage media format that can... Read More
It's most peoples worst computing nightmare. You wake up in... Read More
If you are like most student's, money isn't exactly growing... Read More
Compatible Laser Toner CartridgesRecently, there has been a huge legal... Read More
The other piece of vital equipment to accompany the rack... Read More
Take a good look at your notebook computer screen. Do... Read More
Get ready everyone, home computers are about to set new... Read More
Most people understand preventive maintenance like changing the oil in... Read More
If you are tight on budget, go for Inkjet Printer.... Read More
Wireless Networking, Part 1: Capabilities and HardwareThese days it isn't... Read More
PC cooling systems are one of the hottest - and... Read More
Protecting Against A Power Surge:Your computer is an expensive investment;... Read More
When comparing refurbished laptop models, ask about these specifications:Central Processing... Read More
IMO, these sd work 'like a VCR' as far as... Read More
So you finally have that new laptop you have been... Read More
Soon the human brain will be completely interfaced with the... Read More
The importance of a bar code reader in this day... Read More
Even with the popularity of digital technology, and the availability... Read More
The Power Supply convert's your regular household current into low... Read More
So you need to check your IP address, for whatever... Read More
Expansion Cards Part 2: AGPThe first in this series of... Read More
Nvidia has done it again, with it's newest video card,... Read More
Hewlett-Packard is, along with Brother and Samsung, one of the... Read More
TiVo will change your life... for the better. Plain and... Read More
High density digital versatile disc is a digital optical media... Read More
As the proud owner of a laptop computer, you'll want... Read More
Here's how to format a hard drive (Legal Stuff: We... Read More
A couple of the recent Tech Tips from www.geeks.com have... Read More
Notebook computers are becoming very popular. They seem to be... Read More
Contrary to popular belief, tape drives are generally robust and... Read More
As we study the issues associated with teaching kids in... Read More
The proliferation of portable DVD players has dramatically changed the... Read More
It appears we need to further streamline health care and... Read More
Take a good look at your notebook computer screen. Do... Read More
I came across quite a number of questions about electronic... Read More
The process of adding USB 2.0 ports took no time... Read More
Have you ever felt like throwing the fax machine out... Read More
TiVo will change your life... for the better. Plain and... Read More
Keeping Shipping Costs DownWhen shopping for inkjet printer cartridges online... Read More
The Pocket DVD Wizard allows you to make backup copies... Read More
A cheap ink cartridge is sometimes the only way that... Read More
Ever wonder where all the cool gadgets come from? Ever... Read More
CCNA and CCNP candidates hear it all the time: "you... Read More
Are you sick of all the high priced notebooks out... Read More
If you are like most student's, money isn't exactly growing... Read More
Day by day computers are getting advanced. Capacity and performance... Read More
Computer MiceEvery computer user can hopefully identify their mouse and... Read More
Are you sick of viewing everything on that small screen... Read More
Tablet PCs are great. If you are a mobile person,... Read More
The other piece of vital equipment to accompany the rack... Read More
With the dropping prices on digital cameras and digital media... Read More
Nowadays, more and more monitor comes in with flyback transformers... Read More
The Celeron and Pentium Processors are two of Intel's best... Read More
To Wire or Not to Wire Wireless networks... Read More
The gaming laptop is coming of age! It is steadily... Read More
Most HP and Epson printers are drop on demand printers.... Read More
Human beings are scaling new heights day by day. Markets... Read More
Surge Suppressors ? A First Line of DefenseAll home theater... Read More
Rear Projection Television - An Affordable OptionA great deal of... Read More
A revolution in learning technology has taken place. Actually, it... Read More
Computer Hardware |