Why Powered USB Is Needed, Part 1: The Short History of USB

This article describes a version of USB that is not related to the new USB 3 spec that Intel has released for 2010 products

The Universal Serial Bus, or USB, is right now the most common serial peripheral bus in existence. Allowing all the most common devices to connect to your computer, to each other, through hubs, and now even wireless USB has become the dominant method of low bandwidth communications between devices and their peripherals.

However, USB is not without flaws, in fact, it has tons of issues that other less accepted standards have already solved, and USB has either not solved them or solved them only recently. One of those problems is that, although USB does provide electrical power to peripherals, it is rarely enough to run devices that suck juice like no tomorrow. Powered USB exists to solve this problem.

I will tell you why Powered USB will never be widely accepted, and also why we need it. However, to do so, this article is split into two three parts: the first part discusses the history of USB and previous peripheral ports, and why it it became widely accepted, the second part contains the meat of my argument on why Powered USB is both needed, yet failing to be accepted, and the third part describes a possible future USB 3 specification in detail.

This is part 1. Part 2 is available here, and part 3 is available here.

Short History of Common Yet Totally Incompatible Peripheral Bus Implementations

Way back at the beginning of time, before Pentiums, before laptops, even before CDs, there was the IBM PC. Although not the first of its kind, it was the first home computer that took off, and along side it riding the new technology boom was the Apple II.

That said, the IBM PC had something unique for its day: a keyboard that wasn’t built into the case. The plug this keyboard used was typically called the AT keyboard port1, named after the IBM PC-AT family of computers. This plug was about a half an inch in diameter, round, and had 5 pins.

This wasn’t the only peripheral socket that IBM PCs had. Some had serial ports (using the RS-232 9-pin or 25-pin standards) going by the name of COM ports. Also featured on some IBM PCs was the Centronics parallel port (using a DB-25 style plug) going by the name of LPT or Printer ports.

So, now, we have three plugs on the IBM PC: one for your keyboard, one for low bandwidth devices (such as dial-up modems and mice when they came into the picture), and one for high bandwidth devices (such as printers, or Iomega Zip drives and external CD burners when those showed up). Does it end there? No.

A bit of time later, Creative Labs added a Joystick/MIDI dual function port on their SoundBlaster series of sound cards. IBM added a new pair of ports called PS/2 ports that used two small quarter-inch 6 pin plugs for the keyboard and mouse (replacing the AT keyboard and serial mouse combo). External SCSI showed up allowing SCSI drives in special external enclosures, and even some document scanners used SCSI as well.

Notice up to this point I have only written about the IBM PC. The Apple II I mentioned earlier had it’s own series of plugs that served the same exact functions. Apple II series computers had serial ports (not including the standard RS-232 serial ports which were compatible), ports for external floppy drives, ports for joysticks, ports for external hard drives. Macs shipped with the Apple Desktop Bus (ADB) for keyboards and mice, and the Apple IIGS shipped with ADB ports as well (in fact, before Macs did, although the Mac design team invented ADB).

None of the ports on the same machine were compatible with each other, and (except for external SCSI and RS-232 serial) none of the ports that served the same function that were used on IBM PCs and Apple computers were compatible with each other either. Confusing, isn’t it?

So, by the mid 1990s, there were a multitude of plugs all serving essentially the same tasks over and over, and all of them doing it incompatibly. USB was born for one specific purpose: to get rid of all these different ports and combine them into one big peripheral plug standard.

One Port To Rule Them All

In 1996, the USB Working Group brought forth USB, the best thing to happen to computer peripheral design in a long time, and within 5 years most if not all of the devices I mentioned before were using USB. You could get keyboards, mice, joysticks, printers, scanners, external media drives, external hard drives, dial-up modems, and a hundred other things with USB plugs.

Now you could build a computer with only two or three kinds of plugs and never have to worry about how to explain to your grandmother what the difference between SCSI and PS/2 is and why she can’t plug her new printer into either of them.

By 1998, all Apple Macintoshes2 were also shipping with USB, and they dropped the legacy ADB design as well. By 2000, some computers were shipping with hardly any legacy ports at all, and laptops went down to the bare minimum of two or four USB plugs with a parallel port (due to the corporate world still having tons of really old printers and that they wouldn’t replace until they stopped functioning) and sometimes PS/2 plugs if you were lucky.

The USB designers did foresee you wanting to use your old devices, however: there are USB converters for parallel port, serial port, PS/2 port, and SoundBlaster joystick devices so you never have to leave devices behind if you don’t want to. In addition, there are port converters for almost any other simple type of device out there, so USB really opened the doors for this sort of thing; the icing on the cake, of course, was when someone made converters to turn controllers from virtually any classic or current game system into USB gamepads.

USB Fixed Problems

USB solved a very important problem: we had too many competing plug designs. Not only was it confusing for end users, it was costly. Why have six plugs of all unique designs, when you can have six plugs of all the same superior design?

USB also solved another very important problem: when you have four plugs, you will have eight or more devices to plug in. The USB standard added concentrator hubs to allow the end user to plug a bunch of devices into a single plug and have all the devices work normally.

USB, while on a roll, partially fixed a third very important problem: some devices require a small amount of power, and it’s a hassle to run yet another cable to an AC adapter (for laptops in the field, this wouldn’t even be possible). USB provides some power to devices, up to a half an amp at 5 volts. You can run almost anything on this except traditionally large devices like printers, some scanners, external media drives, and hard drive enclosures3; those require external power supplies. In addition, though this wasn’t intended when the USB Working Group designed USB, some devices recharge their batteries via USB, including a brand of AA batteries that they themselves recharge over USB.

This partial fix of the third problem is where Powered USB comes in.

Read part 2.

[1]: The IBM PC-AT was the second generation of IBM PCs. The first generation, although using the same exact plug for the keyboard, did not have compatible keyboard types.

[2]: I’d like to say thanks to Steve Jobs, for if it wern’t for Macs pushing USB, they wouldn’t have become popular on PCs; before that, they were only shipping with maybe one or two plugs plus PS/2 keyboards and mice.

[3]: This is not entirely true. There are a couple USB hard drive enclosures for 3.5″ hard drives that use 2 plugs to get 1 amp, and most 2.5″ drive enclosures run on half an amp (usually) fine. It is considered a bad hack to use the two plug method required by drive enclosures, and I suggest if your enclosure offers the use of an AC adapter, use it.

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Transmissions from the Little Blue Marble

Published March 29th, 2007


48 Responses

The USB was first imagined at Intel in 1990-91 by Wynn Smith who formed the Hunacre group. Ralph Smith, one of the group’s engineers has the original prototype.

The article says:

“In 1996, the USB Working Group brought forth USB, the best thing to happen to computer peripheral design in a long time”

It was the best thing to happen to the computer in a long time – it changed the way we all work. However it was invented by Wynn Smith back in 1990… Intel didn’t even see the future potential of the USB and shut the Hunacre project down. The upstream/downstream patent is in the name of the Hunacre engineers.

that was totally WICED

After see this i just say this SUPERB

I couldn’t have said it better myself! Thanks a lot!!!

great article, I love your style. All the best green this commentary comes out of England.

I would like to add to your statement about IBM PC and Apple II’s. The Apple II was introduced in April 1977. The IBM PC was only introduced in 1981. Thus, the IBM PC is substantially later than the Apple II.

Subsequent IBM and Apple computers leapfrogged each other. In 1983, Apple introduced Lisa while IBM introduced XT. In 1984, Apple introduced Macintosh with a graphica interface in January 1984. The IBM AT was added in August 1984 and Windows 1.0 came out in 1985.

From the beginning, Apple computers always bundled state-of-the-art communications. In the 1980’s, serial ports were state-of-the-art. The Mac Plus was amongst the first computers to incorporate a SCSI port as standard in 1986, as well as 2 ADB and 2 serial ports. This remained pretty much the standard package until 1999. The iMac offered 2 USB ports in 1999 and most of the desk top and portable macs offered 2 Firewire ports. Since 2001, they have offered ethernet 1000Base-T. Since 2003, Apple has provided USB 2.0 ports and Firewire 800 as standard on all their computers while airport and bluetooth were optional. By 2004, airport extreme and bluetooth were available on all Macs and standard on some. Bluetooth 2.0 was available in 2005 and standard by 2006. A built-in video was standard in 2006.

The only major competitor to USB is Firewire which now is standard on all Apple, some Dell, and Sony computers. The original iPod had firewire but switched to USB. Because Sony video cameras adopted firewire, most major brands of video cameras also include firewire. According to Wikipedia the more expensive hardware required for firewire is the main reason why firewire has not displaced USB.

Firewire can connect up to 63 peripherals and supplies up to 45 watts of power per port at 30 volts, sufficient for moderate-consumption devices. Firewire 400 and 800 respectively transfer data at 400 and 800 Mbits/sec. While USB 2.0 can theoretically transmit at 480 Mbits/sec, such speeds are seldom achieved in practice due to the server-client architecture of USB devices. Firewire provides peer-to-peer network operation and support for memory-mapped devices, which allows full-speed communication.

Firewire is particularly useful for networking computers and high speed transfer of data from one computer to another. That is why firewire is so popular for digital video. Firewire connections can also be “hot-swapped” without damaging the attached device. In the end, the increasing popularity of video will drive development of Firewire and keep it alive. For example, firewire copyright protection standards have yet to be broken and one of the latest developments is wireless Firewire (Source)

Way back in 1979, the extremely old Atari 400/800 line of computers had a universal serial bus. It was slow, and had a bulky connector, but this was only 1979.

You connected RS232 ports, printers, floppy drives, and eventually even hard drives to the same serial bus in a daisy chain configuration.

People laughed and said “why would anybody want all those devices to share the same interface?” It’s too slow (which was true, but that was a different problem) and it didn’t solve power distribution problems either, but it predated IBM PC’s and AT’s by many years. Judging by your article, they were years ahead of their time.

Game port adapters (of the DB-15 connector type) were available from IBM for IBM PC, as were the analog joysticks pluggable for them — and this was far before Creative Labs was around. Which company and when came up with the idea of using the same port for MIDI as well I don’t know; that could’ve been Creative.

I tend to agree that USB is embarassingly incompatible after nearly 10 years of use.

For storage peripherials, especially when more than one device is connected, Firewire absolutely RULES! For mice and keyboards, USB 2.0 is OK.

I use both Macs and WIndoze every day. The Macs have FAR fewer USB problems then the Windoze PCs (mostly IBM and white-box). As indicated above, the Windoze drivers issues are a shame after nearly 10 years of USB being in use and still being clumsy and having only about a 50% chance of working as plug-and-play. Needing yet another driver for a simple mouse is just plain wrong!

Just my $.20 worth (adjusted for inflation)

A minor quibble – the Apple II (or, rather, the Apple ][ ) was the first wildly successful home computer. It came before the IBM PC. The IBM PC was the first wildly successful business computer, though Apples were also used in business by that time.

The one part of the history he left out was that in 1998 while most IBM PC’s had a USB port, none of the peripheral manufacturers were making USB devices. When Apple announced going to USB, this forced that segment (Mac peripheral market) to go to USB – and it exploded. In a year you had gobs of USB devices, for both the IBM PC’s and the Macs. Apple’s move made USB take off – we owe the kudos to them.

As anyone who actually owned one knows, the original IBM-PC had TWO round, 5-pin connectors; one for the keyboard, the other for the Cassette Tape interface, which was the only mass storage available for those without the extra $500+ to own a floppy drive.

The parallel interface was provided on the monochrome video card, if I remember correctly.

You said “Macs introduced the Apple Desktop Bus (ADB) for keyboards and mice, and the Apple IIGS shipped with ADB ports as well.”

That’s not right. The Apple IIgs shipped with ADB before any Mac shipped with it. The Apple II team saw the ADB standard that had been developed by the Mac team, and decided to use it on the IIgs. It ended up shipping before the Mac SE and Mac II that were the first Macs to use the standard.

You said “none of the ports that served the same function that were used on IBM PCs and Apple computers were compatible with each other ”

That’s not really true either. An 8-pin mini-din serial port on an Apple IIgs or Mac was electrically compatible with DB-9 or DB-25 serial ports as found on IBM computers. You just needed the correct cable. Also, the 15-pin monitor connectors on both Macs and PC’s was electrically compatible; you just needed a DB-15 to HD-15 adapter or cable.

As another poster mentioned, you totally left out the impact that the original iMac had in jumpstarting USB. Since Apple was the only company with the guts to completely drop all legacy ports at one time, users were forced to buy all new USB peripherals. Anyone around in 1998 will remember all of the new USB devices and adapters, all shipped in Apple-like translucent fruit colors. As for PC’s, they only stopped putting the PS/2 and parallel ports on machines very recently, even though adapters have been available for nearly a decade.

“This plug was about an inch in diameter, round, and had 5 pins”

It is about half an inch in diameter.

The IBM-PC wasn’t even close to being the first home computer to take off: that was the Commodore 64.

Also, there were MANY computers as far back as 1979 that were the size of the IBM PC (or smaller) that had external and detachable keyboards. I was there, I was programming them.

Please learn your facts before stating this type of mis-information.

HEY SKIP! A little bit of HISTORY there… Apple WASNT EVEN ON THE SCENE YET when the Altair made its debut in 1974. I remember getting mine in 1975. It took forever for all the little parts and pieces to arrive and you had to hand-assemble the thing (meaning solder the chips to the boards and everything). But they were GREAT computers. And the rich kids got the IMSAI (a la “War Games”) I always wanted one of those. But there were still other computers that were available even before that- such as the Mark-8 (Plans only, you had to track down the parts and build it yourself), or the KIM-1, of about the same vintage as the Altair, an early 6502-based system. I had one of those too– lots of fun. There was a THRIVING personal computer market BEFORE the IBM or APPLE computers came along. All those companies really did was a good job at “consumer-izing” them and marketing them. Kudos to them, don’t want to take away from their accomplishments– but to remind that there were lots of other systems around and the market was truly established long before either IBM or APPLE hit the scene. BTW– Bill Gates and Paul Allen both got their start at MITS, the company that produced the Altair. How’s that for history?

I still use a scanner to this day, A cannon scanner (which is a mustek scanner under the hood) that draws all of its power from the USB port. And it does a fabulous job scanning and is very quick too.

Why stop at the IBM PC’s? There were yet even earlier personal computers, such as the Altair, IMSAI (S-100) examples running CP/M, and Rat Shack, and others– that all had their significant contributions to the modern world of desktop computing. I hate it when people think IBM hung the moon. Ever wonder WHY all those printers had a “Centronics” style connector??? They were POPULAR BEFORE IBM made personal computers. If you can believe that! Youngsters… what can you do??? 🙂

Skip — the original Apple ][ didn’t have any standardized ports either. Things were usually connected by the means of ribbon cables fed out from holes in the back of the machine. Apple didn’t start standardizing ports until the Macintosh and the Apple //c, both well after the IBM PC came out.

Pardon my creaking memory here, but “the AT keyboard port1, named after the IBM PC-AT family of computers. This plug was about an inch in diameter, round, and had 5 pins.” sounds a bit big to me. I seem to remember that the diameter of that plug was about 15mm (millimeter), which sounds like half an inch to me. The PS/2 keyboard port was more like 8-9 mm which is about 1/4 inch, isn’t it?

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