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Behind The Scenes
IEEE1394 better known as the name introduced by Apple FireWire (or Sony iLink) and USB 2.0 (or USB HighSpeed as their promotors call it) are the revolutionary modern buses for peripheral communication not only for computers but consumer electronics as well. These two bus technologies have been each others rival since the day they have been announced and they both claim that they're better and faster than all of the classic bus types such as RS-232, Parallel Port/ECP/EPP and even local buses like ISA and VESA.
First lets take a look at the idea behind those two new bus technologies and what makes them different from the ones in the past.
As the computer technology develops users have to deal with a lot of information. PC is not just like your TV set or toaster just plug it in or turn on and it works. No, it's still very far to be the first electro furniture to be at our homes. But it's getting into our lifes more and more.
Although the PC market enlarges, the hardware industry cannot maximize their sales due to couple of reasons. You cannot just go to your favorite shopping mall or supermarket and buy new toys to use with your computer. It requires users to be technically sophisticated to install the new hardware. Therefore they still go to the computershop at the corner with their computer under their armpits to buy and install the new hardware. You have to be a little bit handy with the tools as well, first you have to unscrew the cover of your computer, than remove the slot and find and appropriate place to your add on card amongst all the cables and the delicate components. Insert the card and screw it. But don't close the cover yet, you have to test it first and if there are no hardware conflicts between your new add-on and the existing ones, you have to figure out a way to solve the problem, IRQ's I/O ports jumpers...Then install the drivers restart the computer. Well this part can happen several times, remove software,shutdown your PC, tackle with the card, turn on the computer, install the software, restart the computer again...
A lot of work, and you really have to have some technical knowledge perform these. That's the why you don't or can't buy it from you favorite shopping mall. And that's why PC couldn't be like your TV set or toaster. Also the extension slots on your computer are limited and most of them were also filled with video adapter, soundcard, network card leaving almost no empty space for new add-ons.You might appreciate that this has a great impact on the computer hardware sales. Because they cannot just sell the electronics, because somebody has to provide the maintenance and support. And for a few bucks of profit you have to be loyal to your consumers till for a year or two (minimum standart
warranty period). There's also a problem that hardware vendors have to design a version of their for add-on for different platforms. (e.g. MAC, PC, Sun)Since the computer technology emerged, there was always a standart hunchback at the back of your computer; RS-232, Parallel Port, Keyboard/Mouse. They were there forever the day the first minicomputer created, when CPU's are operating at the speeds of half Ghz they were still communicating with it at 512Kbit/s or 115Kbit/s (recently) at max. You wouldn't use it to connect a scanner or a video camera which requires around 1.5 Mbit/s.
Operating System vendors also having problems cause users are having a lot of trouble when installing a new peripheral.
Thank god this misery is ended for everybody. USB 1.0 was the first real implementation of (hot) plug'n play. Theorically you can just go buy a USB gadget to plug in your computer directly even your computer is running on. And your operating system recognize your device by the time you plug-in and loads the necessary software without even asking you. Plop!!! Within a few seconds your new toy is on the run, no reboots no ugly blue screens for hardware conflicts, no driver diskettes !!!
That's why you suddenly see even at your newspaper kiosk all sorts of computer gadgets.And of course hardware vendors improved their sales figures.
USB 1.1 supports hot plug'n play, with a bandwith of 12 Mbit/s and you can connect up to 256 to one USB interface (with port multiplier hubs). And devices can be powered directly from the bus, meaning no additional power cables, adapters etc. You can connect almost every peripheral, including your digital camera, mouse, keyboard, modem, printer, monitor, scanner, backup unit, floppy drive, palmtop.
And you can share your peripherals with other computer brands or non computer appliances (for ex. connect a printer to your direcly digital camera). Unfortunately, your total bandwith 12 Mbit/s and it's not endless compared to your eagerness to add more devices. But still you can operate 5-6 fullspeed
devices (keyboard and mouse are low speed devices) simultaneously at a satisfactory performance.What happened was this way of consuming is very much appreciated that a huge demand for new things raised. Now people want an external harddrive, DVD-Player, CD-RW and hi-resolution cameras with the unbearable comfort of USB. And this seemed to be problem for USB technology promotors.
From the day that it began USB was always an initiative of a group so called WINTEL, (Microsoft, Intel) and others such as Apple were quite critical about the way USB was. So that Apple decided to design their own new bus called FireWire, and some of them just preferred to wait who comes first. FireWire meant to be a very high speed bus from the very begin with a bandwith of 240 Mbit/s. This of course rivaled the throne of the USB 1.1 with its 12Mbit/s bandwith. So behind the scenes USB Group (USB-Implementors Forum), decided to defend themselves against this attack and they started working on USB 2.0. But they weren't ready to cope with a speed like 240Mbit. They announced in a hurry that a highspeed version of USB which will be 100% compatible with USB 1.1, is coming up. It was a marketing movement to convince the users and the hardware vendors that USB is there to stay. Of course engineers had no idea how to achieve that speed whilst being 100% backward compatibility. When they were just figured out a way, but a news flash came in Apple have seen their bluff and was going for 480Mbit/s. And a counter attack from the WINTEL group came in secretly, guys we're going for 480Mbit/s. This was a real problem because USB 1.1 cables were not suitable for such high speed data transfers. There were a lot of interference due to the high frequency, yet the connector pins were so close. At that frequency range those pins were acting like small transmitter antennas, corrupting all the data. Even the circuit boards had to be designed specially to handle microwave and they have to be insulated from the electromagnetic noise that computer itself generates. Another problem was on the bus powering architecture, from the begin many vendors wanted to increase the power supplied from the USB port, but USB-IF objected to these requests. Now they wanted to connect to the same ports even more devices.
At last most of the problems were solved and Intel have demonstrated first USB 2.0 peripheral a scanner at Tokyo but it was just using a digital interface, but no real USB cable. Then at WinHEC Philips demonstrated first fully operational USB 2.0 device using a standart USB 1.1 cable. It was an external USB Audio Card playing realtime audio data.There's a big reason that Intel is the first one to promote USB, that USB performance depends 100% on the CPU performance since USB is implemented in a client/host fashion. The overloda of data communication is always on the CPU. Meaning that you have to have more CPU power to achieve maximum performance from your USB. More CPU power more Intel sales, an easy logic!!!
This has also benefits for consumers and hardware vendors though. Because shifting the workload to CPU leaves less to do to the device itself. As a result the electronics required for USB devices is much more simpler than peer to peer buses. Less electronics means less cost for the vendors and cheaper products for the consumers. Nowadays, you can implement USB with a single chip on your device, with an additional cost about half a cent!In contradiction to USB, IEEE 1394 supports peer to peer communication which shares the process load between the device and the CPU. Although this increases the complexity of the electronics on the device (and the price), it is quite suitable for the devices that produce a lot of data to process like DVD players, digital cameras etc. This way before the data is transferred to the computer it can be processed on the device and sent when the device thinks it's necessary. You can also connect to 1394 devices to each other but you cannot do the same thing on USB, you always need a host to manage the communication.
Centrillium IT Consulting
10.05.2001, All rights reserved.
Centrillium IT Consulting provides expert consultancy services for IEEE 1394 and USB 2.0.