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USB (Universal Serial Bus) and FireWire (IEEE 1394) Serial Ports - Page 2

USB/FireWire problems and solutions

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More USB information

USB devices are attached to a PC via USB ports, which can be incorporated in the motherboard, added by an expansion adapter card fitted to the motherboard, and can even be found incorporated in monitors and keyboards.

USB ports built into the motherboard can be part of the main ports panel, or can have connectors (headers) on the motherboard itself that are attached to cables that are screwed into a ports' face-plate The face-plate is installed (in the same way as an adapter card is) in one of the free spaces at the back of the case that have removable blanking plates over them.

The only occasion that I have come across in which a USB device was damaged just by being connected to a computer was when someone used the wrong cable to connect extra USB ports to one of the motherboard's USB headers by making use of a USB bracket that fits into a slot at the back of the case like an adapter card. The reason it happened was because different motherboards - even made by the same manufacturer - can use different USB header pin arrangements that require a cable that matches that pin arrangement. Therefore, using the wrong cable will connect the wrong wires to the pins of the header, which can cause damage to any device that is connected to the USB port.

If you have any doubt about the validity of a particular cable and motherboard setup, you should first try connecting a cheap USB device, such as a mouse, to a port.

Any peripheral device such as the keyboard, mouse, printer, scanner, and modem that supports a USB connection can be attached to a PC's USB ports - or externally via a USB hub.

USB 1.1 was the standard that was initially available on PCs, but USB 2.0 was released in April 2000, and it is now available in new PCs.

The new standard is backward compatible to the previous standard, so you can attach a USB 1.1 device to a USB 2.0 port. You can also attach a USB 2.0 device to a USB 1.1 port, but it will only function in the USB 1.1 mode - or at 12 Mbps.

The 12 Mbps (megabytes per second) data transfer speed of USB 1.1 represented a major leap forward in performance compared to the previous serial and parallel ports, which are much slower - 2Mbps for a parallel port and less than 1Mbps for a serial port.

But that is nothing compared to the difference between version 1.1 and version 2.0.

USB 2.0 has an incredible bandwidth (data transfer capacity) of 480 Mbps. The ability of USB 2.0 to run USB 1.1 devices is guaranteed, so existing devices won't be rendered obsolete. However, USB 1.1 hubs can only accommodate USB 1.1 devices. Therefore, if you want to attach USB 2.0 devices to a PC via a hub (three linked hubs with as many as 127 devices attached is the maximum capability), you will have to purchase a USB 2.0 hub, which, thankfully, will work with USB 1.1 devices. You will also be able to run a USB 2.0 device on a USB 1.1 system, but the bandwidth will be 12 Mbps instead of 480 Mbps. .

USB has far superior bandwidth to ordinary serial ports, which transfer data a bit at a time in series, and parallel ports, which usually transfer data 8 bits, or a byte, at a time along eight channels in parallel. This is because instead of transmitting information one bit or byte at a time, USB components transfer predetermined sizes of packets of information that are typically 8, 16, 32, or 64 bytes in size.

Note that only ATX form-factor motherboards come with built-in serial, parallel, and USB ports, so the old-style AT and Baby-AT form-factor motherboards (now redundant technology) can only use USB if the USB ports can be attached to a riser card containing them that fits to the motherboard, or by installing a PCI USB card (of the kind shown further down this page) that provides them.

An increasing number of devices of all kinds from mice to printers and scanners are now able to be connected via a USB port, which, since it requires only one of the sixteen IRQs (Interrupt Requests), is a saver of system resources.

An IRQ allows the various active components in a computer to request and be granted processor time. A device uses its IRQ to request access to the processor. There are usually only 16 of them - from numbers 0 to 15, but a BIOS setting called APIC mode written about at the beginning of this article can allow Windows 2000 and XP systems to use twenty three.

USB plugs are small - about half an inch across and rectangular. Any relatively recent ATX motherboard will have at least two built-in USB ports. Click here! to see images of the built-in ports of ATX motherboards. Use your browser's Back button to return here.

Numerous - over a hundred - USB-compliant devices can be attached to one USB socket, usually via one or more USB hubs - with all of them using only one of the IRQs.

Note that if your version of Windows supports USB, a USB Controller will be listed in Device Manager.

USB also has to have BIOS support enabled. In an Award BIOS, the setting appears in the Integrated Peripherals as USB Controller.

You may also have seen a "Legacy USB support" setting option in your BIOS. This is for USB-based input devices (like the keyboard or the mouse) that are being used in non-USB systems. DOS, for instance, won't recognise USB devices on its own.

If you are using a computer running a version of Windows 95 OSR 2.1 or Windows 98, Me, and XP that supports USB, you can disable this setting without having any affects on the use of USB devices. But if you are using a DOS system, or a non-USB version of Windows 95, you should have this setting enabled in order to be able to use a USB device.

USB Networking

The usual way to network two or more computers using USB connectors is to install USB network cards in each computer, and link them with USB cables via a USB hub.

But it is also possible to build a wireless USB network that takes signals from a wireless USB hub via special USB connectors, such as the one shown below that is made by 3Com.

3COM wirless USB nnetwork connector

Moreover, it is also now possible to buy a special USB cable that networks two or more computers.

You do not need anything else, just this cable, an image of which is shown below. You will, of course have to install the drivers that come with it in order to make the cable function in the same way as two network cards and a cable. You can network as many computers as you like in this way.

USB networking cable that can network two computers without the use of a hub or anthing else


Always use only a special USB networking cable to link two computers.

The following thread I found on a computer forum provides the reason:

"Never connect two PCs with a standard A-A USB cable! USB carries +5V and you can permanently damage one or both PCs! You need a specific USB device for this." -

"The A / A cable or "extension" - would it actually fit between two computers?"

"An "extension" cable is male A to female A. Double-male A cables are rare, but people seem to find them. They are absolutely deadly."

See the Networking page of this site for more information on USB, FireWire, and other types of networking.

Using a router with USB ADSL or cable modems

If you connect to the Internet via a USB ADSL or cable modem connected to a router, read Why can't I find a router for my USB DSL modem? if you need an answer to that problem. - Use your browser's Back button to return to this point on this page.

A USB-to-IDE box

If you have ever wanted an extra hard disk or CD-ROM drive for your portable computer, or even a desktop PC, you can purchase a USB-to-IDE box for around £60.

The box contains all of the electronics to convert an IDE interface, which most hard disk and CD-ROM drives use, into a standard USB connection. In effect, you use the box to convert IDE drives into an easy-to-fit, quick-to-swap USB unit..

In addition to USB-to-IDE adapter, there are adapters available that allow you to connect almost any device to a USB port.

There is the Belkin USB Parallel Printer Adapter. However, it is not possible to have a bi-directional printer adapter, so the parallel printer adapter cannot be used for scanners or Zip drives. Consequently, most printers will not be able make use of their bi-directional capabilities in which they communicate information to the computer, such as ink levels and battery power.

You can make use of a search engine to find vendors and more information on the above-mentioned products.


Drawing of a FireWire (IEEE1394) port

The diagram above shows the shape of a Firewire (IEEE1394a) port. To view images of FireWire cables, visit:

FireWire -

The FireWire standard of data transfer is dying out. Now only tape-based camcorders have FireWire connections. Modern camcorders and cameras use the USB standard, the latest of which is USB 3.0, which is dealt with on Page 1 of this article. FireWire was always more commonly used by Apple (called iLink) rather than Windows computers.

Because of a lack of devices using the data-transfer standard, PC motherboard manufacturers are opting not to include a FireWire port on their motherboards for desktop and laptop computers. However, FireWire ports can still be added by installing a PCI adapter card in a desktop PC that usually provides two ports. Note that some motherboards provide a FireWire header on the board, but don't usually provide a FireWire backplate that contains the ports, which fits into an empty outlet at the back of the case like any other PCI or PCI Express adapter card. Such a backplate, which has the cable that attaches to the header on the motherboard, can be purchased for around £5.

If you have an old camcorder that uses FireWire and you are buying a new desktop PC, you can ask the store to add a FireWire adapter card. A FireWire CardBus card is a credit-card-sized connector that fits into the PCMCIA slot on a laptop PC that provides two FireWire ports. The latest laptop adapter-card standard is called Express Card and FireWire is available for it as well.


There are two FireWire standards - the original 1394a (FireWire 400) and the upgrade, 1394b (FireWire 800), which doubles the original bandwidth from 400Mbits/sec to 800 Mbits/sec.

Note however that although the data-transfer speeds of FireWire 800 beat those of USB 2.0 by a wide margin, SuperSpeed USB 3.0 crushes the data-transfer speed of FireWire 800.

USB 3.0 will crush eSATA, FireWire -

Page 1 of this article provides information on USB 3.0, which is now available on desktop and laptop computers and on adapter cards for both desktops and laptops, which provide USB 3.0 connectivity on computers that don't have it built in.

Before going any further into this article, read this Q&A on this site: I pushed the FireWire connector into the FireWire port on my PC the wrong way around and fried the iLink board on my camcorder. Use your browser's Back button to backtrack.

FireWire 400 ports have become standard on most new desktop PC motherboards. Most new midrange laptop PCs provide a FireWire 400 port for connection to a camcorder. FireWire can be added to a desktop PC via a PCI FireWire or PCI Express adapter card and to a laptop PC via FireWire 400 or FireWire 800 CardBus cards and ExpressCards.

The first devices that use FireWire 800 arrived in 2003, but the interface is still (May 2008) relatively uncommon on PCs (desktop and laptop). Most PCs have only a Firewire 400 port. However, FireWire 800 has been available on Apple Macs for some time.

Read Expanding a laptop's capabilities with PC Cards on this site for more information on those expansion cards.

Note that some desktop PC PCI FireWire adapter cards may not support the full speed of FireWire 800, especially when fitted to a 32-bit slot. Therefore you should check the manufacturer's specifications, because you may have to use a 64-bit PCI slot. The PC's motherboard manual will specify which type of PCI slot the motherboard supports. If you don't know the make and model of the motherboard installed in your computer, here is a good free utility - Belarc Advisor - that creates an analysis of the hardware and software on a personal computer. Look under FREE DOWNLOAD on Another utility that also provides information on the motherboard is CPU-Z from You can then use a search engine to locate the manufacturer's website. Alternatively, you can use a PCI Express card instead, if the PC's motherboard provides the required slot.

The higher licensing and hardware costs of FireWire has resulted in the USB interface being used for most peripheral devices. However, FireWire has established itself in specialist areas. For example, it has become the main standard for connecting DV camcorders to desktop and laptop computers in order to transfer video between them. Because the standard guarantees bandwidth to a connection, it prevents the dropping of frames when working with real-time applications. For that reason, it has become invaluable for video-editing and for connecting to an external hard disk drive.

The full-size, six-pin plugs of FireWire 400 (1394a) can deliver up to 45W of power to devices, which allows them to be powered by the port. However, the mini four-pin ports used by most camcorders don't have the pins that supply power.

FireWire 800 uses a new type of connector that has nine pins in a square-shaped plug. It is backward compatible with the original FireWire 400 standard, but a special cable with a nine-pin 1394b plug at one end and a six-pin/four-pin 1394a plug on the other. Data-transfer speeds drop from 800Mbits/sec to 400Mbits/sec if you connect a FireWire 800 device to to a 1394a port or link it to a FireWire 400 device. For the full 800Mbits/sec data-transfer speed, a FireWire 800 device must be connected to a nine-pin port using a nine-pin cable.

The difference remaining between FireWire and USB 2.0 is that USB 2.0 is still a host-based standard - the peripheral devices must be connected via a computer in order to communicate. But FireWire is a peer-to-peer standard, which means that FireWire devices can be connected together without going through a computer.

USB is very common on the Mac and the PC, but FireWire connections, also known as 1394a (or i.Link - Sony's name for it) while not yet being very commonly found on PCs, are found as standard ports on most digital cameras, Apple Macs, and portable computers.

FireWire (1394a) is much faster than USB 1.1, but only slightly slower than USB 2.0.

However, note that a newer version of FireWire that is theoretically twice as fast as its forerunner, known as 1394b (or FireWire 800 because of its 800Mbit/s (megabits per second) transfer rate, is now available on standard PCI expansion adapter cards (containing FireWire 800 ports, or as network cards) and on some of the latest motherboards.

Click here! to go to a table that provides information on the theoretical bandwidths and the actual bandwidths of the two types of FireWire interfaces. Use your browser's Back button to come back to this point on the page.

It is possible to purchase conversion cables that allow an older 1394a device to be used on an 1394b port.

The maximum length of such a FireWire 400 cable has to be 4.5m to maintain data transfers at full power. However, FireWire 800 has increased that to 100m by making it possible to use Cat-5 network cable or fibre cable.

USB devices have to be connected either directly to a computer or to the computer via a USB hub, but a maximum of seventeen FireWire devices can be connected to a computer in series (one device connected to another) as long as there are two FireWire ports available on the computer, because one has to be used for an input port with another as the output port for the chain of devices. Daisy-chained SCSI drives have to have both open ends of the chain of devices terminated with a terminator, but this is not necessary for FireWire devices connected in series.

FireWire network (NIC) cards are available for both IEEE 1394a and IEEE 1394b, but, although the data transfer rates of a FireWire 800 card are faster than an Ethernet 100Mbit/s card, it is not an ideal networking solution for the following reasons.

FireWire networks run under the latest Linux distributions and on the Apple Macintosh OS X without any known problems, but with Windows, only the IPv4 over 1394 is supported, which only allows for data transfer using TCP/IP. The IP address required for network operation is unlikely to be available automatically via DHCP for FireWire, since no servers are currently designed to be able to do this. This is not much of a problem, since assigning IP addresses manually on a small home network is not difficult.

However, note well that FireWire networking can pose major security risks. Look under Security on for more information.

FireWire 800 external hard disk drives are also available, such as the Fire800 drive from WiebeTech.

You will have to purchase a FireWire PCI adapter card if you want to attach a FireWire device to a PC that doesn't have a FireWire port built into the motherboard. This is an adapter card that fits into a PCI slot on the motherboard. You fit the card and install the drivers that come with it on a CD, and you have a two-port or a four-port FireWire interface.

The 64-bit 66MHz PCI Express standard, now standard on all new motherboards, has twice the bandwidth of the current 32-bit 33MHz PCI standard. Using this much faster bus for FireWire and FireWire 800 adapter cards will remove the major system bottleneck, thereby allowing data transfer rates that are much closer to their theoretical maximum rates. The PCI Express 2.0 standard is in the process of replacing its forerunner. It provides double the bandwidth for data transfers that the original standard delivers.

PCI Express 2.0 to double bandwidth -

PCI Express 2.0 Graphics Cards Tested -,1915.html

Note that PCI Express 3.0 was released in November 2010, but the AMD Radeon 7970, launched on January 9, 2012, was the world's first PCI Express 3.0 graphics card. PCI Express 4.0 is expected to be finalised some time between 2014 and 2015. Reviews of the performance of PCIe 3.0 graphics cards makes it plain that the increase in performance from version 2.0 to version 3.0 is nowhere near the increase in performance between version 1.0 and version 2.0.

PCI Express -

You can purchase a FireWire-to-IDE box, called a FireBox, for around £150, which is almost three times as expensive as a USB-to-IDE box.

You can make use of a search engine to find vendors and more information on the above-mentioned product.

Daisy-chaining several FireWire devices together so that they connect to a single port on a computer

If a desktop of laptop computer only has a single FireWire port, several FireWire devices can be connected to it via that port by daisy-chaining them together.

For information on this subject, read this Q&A on this site: I have daisy-chained several FireWire storage devices to my computer, but some of them are not recognised by Windows.

To read a technical article on FireWire, visit:

How FireWire Works -

For more information and to view images of FireWire cables, visit:

FireWire -

USB/FireWire problems and solutions

Click here! to visit the pages on this site devoted to USB/FireWire problems and their solutions.

The USB and FireWire BIOS settings

Both USB and FireWire devices require that a dedicated software controller that has to be provided by the operating system, which for most people is still Windows. Windows XP supports both USB and FireWire, but earlier versions of Windows might not support either, so always check that your version of Windows supports a USB or FireWire device before you purchase it.

Below are the USB and FireWire BIOS settings for the Abit KT7 motherboard that was available for both the Athlon and Pentium 4 platforms. IEEE 1394 is another name for FireWire.

Note that Abit, in spite of manufacturing well-reviewed and regarded motherboards, went out of business in 2009.

USB and FireWire BIOS settings

Motherboards without the ports for legacy devices

Many of the new motherboards coming out now have done away with all of the legacy serial and parallel ports, and have replaced them with USB and FireWire ports.

The ATX Abit AT7 - which was available on both the Athlon (Socket A/462) and Pentium 4 (Socket 478) platforms - is such a motherboard. Its built-in ports panel looks like this:

The port panel of the Abit AT7 motherboard

From left to right are a block of two USB 1.1 ports, a block of two USB 2.0 ports, a separated pair of IEEE 1394 FireWire ports, full analog 5.1 audio out, digital audio out (five round and coloured ports), and LAN (network) connector ports (far right).

There are no legacy ports, so, with this motherboard installed, so unless you are able to obtain conversion plugs, you would not be able to use a printer that only has a parallel port, a PS/2 mouse or keyboard, a serial external modem, or any device such as a joystick that uses a serial port. You can only use USB or FireWire devices.

If legacy ports to USB (or FireWire) conversion plugs are available, or become available, you will be able to reuse your PS/2 mouse and keyboard, and use a printer that has only a parallel port, etc.

ATX cases are fitted with a removable port face plate that has cut-outs in it that are themselves removed so that the ports on the motherboard fit through them. You remove the cut-outs that match the ports on your motherboard. For instance, you would not remove the cut-outs for an inbuilt video card port or for a sound card's ports if the motherboard does not have inbuilt video or sound ports.

As you can see, the Abit AT7 motherboard has a port profile that is completely different from the standard ATX legacy motherboard's port profile shown above it. Luckily, this motherboard comes with a port face plate that matches its unique port profile, but that might not be the position with other motherboards with similar port profiles. In that situation, you would either have to buy a case that comes with a port face plate that matches the motherboard's port profile, or you would have to install the motherboard with the port face plate removed. So, always check the port profile before you buy a new motherboard.

USB and FireWire problems and solutions

Click here! to access two pages of Q&A articles on USB and FireWire problems.

USB & FireWire websites and webpages

Universal Serial Bus -

USB drivers -

USB How-to -

USB and FireWire cables and adapters (adaptors) -

How Serial Ports Work -

How USB Ports Work -

FireWire -

How Does FireWire Work? -

Apple's FireWire page -

Linux USB -

Linux FireWire -

For more information, try entering "serial ports", usb , firewire, or "ieee 1394" as a search queries and see what turns up. If the search term (or any part of it) uses more than one word, place it between double quotation marks. You can run USB in MS DOS. To find out how, use a search term such as printing + dos + usb, etc., depending on what you want USB to do in MS DOS. - Electronics Buyer Guide

Visit the Electronics Buyer Guide for advice on making purchases of Camcorders, Digital Cameras, DVD Players, Graphics Cards, Handhelds and PDAs, Home Networking, Mobile Phones, MP3 Players, Portable Electronics, Printers, Scanners, Video Editing Cards, Video Recorders, and WebCams.

USB and FireWire hubs

If you use several USB and FireWire devices, USB and FireWire hubs are available of the kind shown in the image below.

Belkin USB 7-Port Hub

USB 2.0/FireWire PCI cards

Add USB 2.0 and FireWire ports to your PC with a PCI adapter card.

Belkin USB 2 PCI Card ( 4 ports)

USB 2.0 adapter cards (installed in a PCI slot on the motherboard) can sometimes have device driver problems or suffer from system resource conflicts with motherboard's that have USB 1.1 ports that can prevent USB devices from being recognised by Windows.

The solution to such a problem would be to experiment with the drivers. For example, look in the Device Manager and click the + beside Universal Serial Bus controllers. If a proprietary controller is listed there, such as one made by, say, SiS, such as the SiS 7001 PCI to Open Host Controller, you can try changing it to the Standard Enhanced PCI to PCI Host Controller. You can do that by right-clicking on the existing entry, and choosing the Update Driver option (in Windows XP). You would select the manual installation option, not the automatic option. You can also change the USB Controller via Add New Hardware in the Control Panel. Installing the latest motherboard drivers, one of which is the USB Controller, can also rectify bugs. You would obtain the motherboard drivers from its manufacturer's site. Obtaining and installing the latest drives for a particular device can also fix problems with that device.

Web searches

If you couldn't find the information that you were seeking on USB or FireWire here, or your particular USB or FireWire problem is not dealt with on the USB and FireWire Problems section of this website, entering usb or firewire or usb troubleshooting, etc., as search queries in a search engine will bring up enough pages to keep you reading about the subject all day. Note that Google is not the only search engine. There are many others just as good, such as Bing from Microsoft, the search engine used by Facebook.

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