Firewire vs. USB: A Comparison
By Nathanael Copyright © Directron.com 2005
Edited by Lee Penrod
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If you have used a computer within the past five years, chances are you've have used USB (Universal Serial Bus) devices many times. From mice and keyboards, to printers and external hard drives, USB devices are nearly ubiquitous in fact; over 1 billion USB devices have been sold.
On the other hand, Firewire-based devices are somewhat less prevalent. Nearly all digital camcorders sold after 1995 have included a Firewire connection, as have all modern Macintosh computers. Additionally, many new external storage devices include a Firewire connector. However, lower-end devices such as mice and printers are rarely (if ever) seen with Firewire connectivity.
In the next two sections, we will look at the history of these two similar I/O ports. Then, we'll compare them side-by-side to see which technology is better for specific applications.
USB: A Brief History
Version 1.0 of the USB specification was released in January of 1996 by the USB Implementers Forum (USB-IF) and was followed up by version 1.1 in September of 1998. A theoretical maximum of 127 devices per controller is specified. Both versions 1.0 and 1.1 support a maximum transfer speed of 12Mbps ("Full Speed") and can fall back to 1.5Mbps ("Low Speed") if need be.
Note that these data rates are in Megabits (Mbps) per second, as opposed to Megabytes (MBps) per second a commonly confused notation.
USB version 2.0 was released in 2000, upping the theoretical maximum transfer rate by a factor of 14 to 480Mbps dubbed "Hi-Speed". USB 2.0 devices are backwards-compatible with USB 1.x devices and controllers, and can fall back to "Full" or "Low" speed in order to coexist with older devices. Nearly all new products on the market are USB 2.0-compatible.
Both USB 1.x and USB 2.0 allow the use of two separate types of connectors Type A and Type B depending on the requirements of the device itself. Type A connectors are almost always used on the host side (computer or hub), while Type B connectors are smaller and are frequently found on the device side in printers, scanners, and other similar hardware.
|A standard USB Type A connector
||A standard USB Type B connector
Both types of connectors can provide up to 500mA (milliamps) of power to connected devices, though devices that require more than 100mA should be self-powered as each USB port generally has a maximum of 500mA of power to share between all devices. A device that draws all of its required power from the USB bus is referred to as a "bus-powered" device.
Windows 95 OSR2 (OEM Service Release 2) included limited support for USB; the original release of Windows 95 had none. Windows 98 and more importantly, Windows 98 SE added much better support for USB, but Windows XP's USB support is the best and most robust, by far. Apple's Mac OS has supported USB devices since prior to version 9.0.4, but this release of the operating system added substantially better support.
Firewire: A Brief History | Go to Top |
The origins of Firewire date back to the mid-1980s. Engineers at Apple Computer devised a high-speed data transfer technology for Macintosh internal hard drives they called 'Firewire'. Realizing the potential for a technology that allowed high-speed transfer to and from hot-swappable devices, Apple presented this technology to the Institute of Electrical and Electronics Engineers (IEEE).
In December of 1995, the IEEE released an official Firewire specification, dubbed IEEE 1394. This specification, sometimes referred to as 'Firewire 400', describes a hot-swappable peripheral interface with transfer speeds of 100 Mbps, 200 Mbps, and 400 Mbps. During the late 1990s, this standard found its way into Sony electronics (mainly digital camcorders) under the title 'i.LINK'. In January of 1999, Apple released what was probably the first personal computer system to include Firewire ports by default: the Blue PowerMac G3. All Macintosh models from then on have included Firewire connectivity.
Firewire cables come in two variations 4-pin and 6-pin. 6-pin cables provide up to 30V of power, allowing for fully bus-powered devices. 4-pin cables do not provide power.
A standard 6-pin Firewire connector.
(Image courtesy of Wikipedia.org)
In April of 2002, the IEEE released an updated Firewire standard, dubbed IEEE 1394b. IEEE 1394b allows for theoretical maximum transfer rates of up to 3.2Gbps. Apple commercially released a subset of this new standard under the title 'Firewire 800' in 2003.
Firewire 800 devices support a maximum transfer speed of around 800Mbps. Firewire 800 adds a new cable type 9-pin cables (also called 'beta' cables), which support the full speed of Firewire 800.
Firewire 800 is backwards-compatible with Firewire 400 when 'bilingual' (9-pin to 6- or 4-pin) cables are used. Firewire 400 devices will still run at Firewire 400 speeds, even when connected to a Firewire 800 host.
The Comparison | Go to Top |
General Peripherals: USB Wins
USB has almost completely replaced older I/O connectors such as parallel, serial, and MIDI (joystick) ports. Instead of a confusing collection of incompatible devices and connectors, you have a one-size-fits-all connection that works on nearly all PCs manufactured in the last 5-8 years.
While USB has not completely replaced PS/2 ports, USB mice and keyboards are readily available. Nearly all recent scanners and printers have USB connections, as do most other low-bandwidth peripherals.
On the other hand, Firewire is almost completely absent from this category. As mentioned before, Firewire is impractical for low-bandwidth devices; this, coupled with the fact that most computers (besides Macintosh) do not include Firewire ports by default, has kept Firewire-enabled devices in this category out of this market.
Digital Imaging/Digital Video: Tie
Firewire is much more prevalent in this category. Almost all modern digital camcorders come with Firewire connectivity. Because of technical differences, Firewire is a better bet for transferring uncompressed (raw) video from digital camcorders, even though USB 2.0 has a higher maximum speed (400Mbps vs. 480Mbps). Not many camcorders have Firewire 800 connectivity yet, but this is expected to change over the next few years.
Most digital cameras still use USB for image transfer. This is likely due to the higher level of compatibility with current computers nearly all have USB ports, while a considerably lesser portion have Firewire ports.
External Storage: Firewire Wins
This category includes external hard drives, external optical drives/burners, and generic external drive enclosures. Though USB 2.0 and first-generation Firewire are nearly neck-and-neck, Firewire can provide much more power over the bus 30V as opposed to 5V for USB, which means that external Firewire drives frequently do not need a separate power brick.
Many manufacturers of external storage devices now produce models that include both Firewire and USB 2.0 ports for maximum versatility. These types of devices are probably the best bet for both speed and compatibility.
Editor Note 1: Real World Performance- Although, in theory USB 2.0 has a higher theoretical bandwidth than Firewire this does not translate into higher real would speed. In most case, a firewire device will transfer data at a higher rate than a USB 2.0 device. This is due to a number of factors including but not limited to CPU utilization and the overhead of the transfer method.
Editor Note 2: Speed Measure- When considering the speed of these two connections please bare the following in mind: The theoretical speed limit of USB 2.0 is 480 Mbps and the theoretical speed limit of Firewire is 400 Mbps, not 480 MB/s or 400 MB/s. Mbps means Mega Bits Per Second not Megabytes per second. 400 Megabits/second equals 50 Megabyte Per second and 480 Megabits/second equals 60 Megabytes per second.
As far as the actual performance of the USB / Firewire interfaces it varies a lot by the PC/Mac and the actual interface in the device -- however, the experience of our techs in general points to a speed loss of at least 20MB/s over theoretical on the USB 2.0 side and often we have seen total speed only being in the 11 - 20MB/s range total. Although we don't have hard numbers on the Firewire side, the average speed difference we have seen in the field is 2x real world speed difference using an external hard drive that offered both types of connections. The firewire connection is usually faster.
For external hard drives, really neither standard produces speeds comparable to a internal hard drive. If you want the full potential from a hard drive you need to go with External Serial ATA. With an external Serial ATA hard drive [Serial ATA Drive + Serial ATA enclosure] you will get the exact same speed externally as internally which is 150MB/s burst or 300MB/s burst depending on the drive.
[Note- 150MB/s or 300MB/s speeds are the burst speeds for Serial ATA drives. We call it burst speed because no traditional hard drive on the market can actually sustain a speed that high. A good modern hard drive is going to give you anywhere between 70MB/s to 85 MB/s sustained speed, and will only give you the full speed of the standard when reading from the cache of the drive]
Conclusion | Go to Top |
USB and Firewire both have unique strengths and weaknesses. USB's ubiquity makes it ideal for devices that require high compatibility with current hardware. Firewire's generous bus power and internal architecture lends well to external storage and digital video applications.
If you have any questions relating to this or any other topic, feel free to post them on the Directron.org Help Desk.
Last updated: 10/10/06
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