Why Powered USB Is Needed, Part 2: The Future 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 2. Part 1 is available here, and part 3 is available here.

Short Introduction to Powered USB

At the end of Part 1, I said USB does not provide enough power for certain devices, a total of 2.5 watts at 5 volts. This is enough for any device that uses little power: keyboards, mice, USB flash keys, etc, etc. Compared to Firewire 400, which can provide similar data transfer performance to USB 2.0, devices can use up to 45 watts at 30 volts.

Powered USB can output 144 watts at 24 volts, 72 watts at 12 volts, and 30 watts at 5 volts (all at 6 amps current), while Firewire does up to 45 watts at up to 30 volts (1.5 amps current), and USB 1.1 and 2.0 does 2.5 watts at 5 volts (500mA of current).

According to recent comments of this article, my original math was wrong: at 24 volts Powered USB only provides three times more power than Firewire, and at 5 volts Powered USB provides five times more power than normal USB.

In Firewire 400 against USB 2.0, Firewire comes out as the better bus for many devices due to the fact that it can supply enough power to, for example, run a two or three drive enclosure or an external DVD burner; not only that, it does perform better than USB 2.0 for data transfers due to the fact you can never get 480mbps transfers in the real world, only around 240 to 360mbps, whereas on Firewire 400 you really can get to 400mbps.

Firewire, for devices that require power and bandwidth, gives USB 2.0 a severe beat down but has trouble taking on Powered USB.

Don’t understand how much power 144 watts at 24 volts is? You can drive printers, scanners, large RAID enclosures, multiple DVD burners for parallel/mass burning, even medium sized LCD monitors. You could drive a pair of large speakers with this much power in addition to sending them digital sound to play.

As you can see in the image, the top part of the plug is the power plug combined with the bottom part of the plug that is a standard USB data plug. This power plug’s power output not being standardized is where everything goes wrong.

The plug did it with the crowbar in the library

The Powered USB specification manages the second half of this (very ugly) plug, where all the extra power comes from. According to the specification, you may have different layouts of power pins to supply 5, 12, or 24 volts, and each plug can only do one of the three.

Can you imagine how confusing this would be to end users? Powered USB has gone back to the days of having incompatible but similar functioning ports on the same computer. Had problems telling your grandmother about PS/2 and SCSI ports, and why she can’t plug her printer into either? Now tell her why she can’t plug her PUSB-5v device into a PUSB-12v plug.

USB does need a powered extension to compete with and possibly eliminate Firewire. I have a dozen devices that have separate power cords and power bricks and it makes for cable spaghetti behind my computer. If all my devices supported some sane future form of Powered USB, I’d lose at least four or five of these power cords.

So how can this be fixed?

For New Powered USB to move forward to the home desktop, I envision that both the USB Working Group and the Powered USB Working Group needs to release new versions of their specifications. First, Powered USB needs a new version (lets call it New Powered USB): they have to standardize on one voltage. I suggest using 12 volts, or use a floating voltage design like Firewire does (12 to 30 volts instead of 30 volts fixed), as this would be most beneficial to devices that require high voltages.

Second, I suggest the USB Working Group should release USB 3.0 already. As I mentioned before in this article, Firewire 400 is marginally faster than USB 2.0, however what I did not mention is that Firewire 800 is about three times faster than USB 2.0 and is already available in a couple devices. I expect to be able to do at least 800mbps or 1600mbps of real performance (akin to USB 2.0’s 240-360mbps real performance) or even more.

Third, I suggest that power strips (the kind you plug your computer into) add USB to New Powered USB bridges that simply pass the USB data over, but add the power pins and power the devices directly from the power strip. Adding these plugs would allow people to power new devices with older computers or with smaller devices (ultra-small laptops, PDAs, etc) that can’t power devices on their own.

With these three suggestions, I can bet you that New Powered USB would become a common home standard, and at least part of the cable spaghetti problem would go away, and I can also bet you that Firewire might also disappear as well.

Continue to part 3.

Written by
Patrick McFarland
Open Source software architect and technologist. He's just this guy, you know? Follow him him on Google+.
Published in
Ad Terras Per Aspera
Transmissions from the Little Blue Marble

Published March 30th, 2007

Comments

70 Responses
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carl0ski
March 31, 2007 at 8:29 pm | Reply

>> Powered USB is the last thing we need. Computers are already using too much power. The environmental impact from using all that electricity will be devastating.

You are joking yes?

The transformer pack required to lower the AC voltage from the wall to the acceptable 12 volts , has a loss of upto 30%.
Thats 30% wastes energy, if that was ofloaded to the somewhat more efficient computer power supply 20% loss
i find that acceptable

Paolo
March 31, 2007 at 6:26 pm | Reply

Im confused as to why you say different pin arrangements to accept the different voltages require different sockets. As you can see the power port has four contact points, we’ll call them 0,1,2,3. 0 we’ll say acts as ground. 1 supplies 5V. 2 12V. and 3 24V.

Rarb
March 31, 2007 at 6:16 pm | Reply

I’m surprised that there’s no mention of another advantage that Firewire has over USB: daisy-chaining. That means that, when using several devices, far fewer ports are required at the “host end”.

CityZen
March 31, 2007 at 5:51 pm | Reply

Kevin, you are making several mistakes.

You are assuming that most people are smart all the time. You’re assuming that everyone reads all the fine print all the time. Neither of these is true. A large number of people are not as smart as you, and even the people who are as smart as you are not smart all the time. Sometimes people get in a hurry and don’t see all the details.

I haven’t looked at all the details of the spec, but from this article it appears to me that there is no such thing as “a (singular) Powered USB Plug”. Rather, there’s Powered USB type X, Powered USB type Y, etc. You can bet your life that many advertisers and people will talk about just “Powered USB” as if there’s only one type, and this will cause problems when people later on discover the multitude of incompatible types.

I can also guarantee you that if the plug looks like it should vaguely fit (but won’t due to minor keying differences), that someone will try to force it to fit because he doesn’t notice the key. I’ve seen lots of computer equipment with broken plugs and jacks for this very reason.

Your last statement regarding how smart people can figure stuff out shows that you missed the point of the article. The article was not addressing whether smart people can figure out the new USB design. It was about whether a large enough number of people would figure out the new design to make the design accepted (and problems in the design that would cause people to not like it).

I’m sure I could design a gadget that works great only when you’re jumping up and down. I’m sure smart people could figure this out. But it’s completely valid for someone to point out that this might cause problems for some people (who might think the gadget is broken because it didn’t work right when they weren’t jumping), and suggest that a different approach might make the gadget more acceptable.

Jared Trent
March 31, 2007 at 4:57 pm | Reply

@ Environmentalist

>Powered USB is the last thing we need. Computers are already using too much power. The environmental impact from using all that electricity will be devastating.

Just because we have a standard plug doesn’t mean we use more electricity. What would you rather have a bunch of bricks converting AC to DC or the computer’s power supply doing it. (My bet is that the bricks use more of your precious electricity)

ArkEngr
March 31, 2007 at 4:40 pm | Reply

There is a larger issue here. Power Systems in Laptops are challaged to provide external power because as a designer you have to balance cost of components against providing features that only a minority need. The typical laptop has 19 volts from the adapter. To convert this to 5 volts for external use results in heat internal to the PC. The heat is proportional to power used.

Teilo
March 31, 2007 at 4:39 pm | Reply

>>Powered USB is the last thing we need. Computers are already using too much power. The environmental impact from using all that electricity will be devastating.

This is a typical enivonmentalist knee-jerk mindless reaction. Please think before typing. If devices use X amount of power now via external klunky power adapters, tomorrow these same devices could use the same X amount of power via an elegant universal powercord.

But they are STILL using X amount of power either way. In fact, they may well use less, because a single high-efficiency power adapter could replace multiple cheap leaky transformers.

Andrew
March 31, 2007 at 4:28 pm | Reply

>>Kevin, you are being an idiot making a point about that.

If powered USB is going to have different cables for each voltage then it’s going to add complexity and confusion, no matter how smart(ass) you are.

Al Dimond
March 31, 2007 at 4:25 pm | Reply

Dude, your calculations regarding electrical power are way off. First, 6 amps is *four* times 1.5 amps, not eight times. Second, an amp is a measure of current. Power is measured in watts. So if PUSB can deliver up to 145 watts at its highest voltage, and Firewire-400 can deliver 45 watts, PUSB can deliver just over 3 times the power of Firewire-400.

john
March 31, 2007 at 4:04 pm | Reply

What’s your problem with firewire? It’s a CPU independent bus with far higher throughput than USB. It’s not for mice or keyboards, so what? Intel never supported FireWire on its motherboards because FireWire did not require a CPU. Intel instead chose to saturate the market with buses that require a CPU, ie Intel) using the junk USB standard.

Also, unlike USB, performance doesn’t stall when devices are daisychained, for example, backing up to a USB drive and video conferencing with a USB web cam–what a joke.

Also, as you say, FireWire doesn’t lie about its actual throughput, unlike USB.

In fact, FireWire permits the system to reserve bandwidth, for example, for realtime applications even if multiple devices are using the bus.

FireWire is more like networking for devices (DV-CAMs, FireWire CAMs, HardDisks, Optical Disks, Hard Disks, whatever…). Its networking like ethernet but with power and auto discoverry.

USB is junk compared to FireWire. PC clowns are fooled again!

– John

David Anderson
March 31, 2007 at 3:56 pm | Reply

What this whole screed boils down to is that ‘Standards are good’ and ‘PUSB isn’t a proper standard, but should be.’ Fair enough.

I have never understood why allegedly intelligent design engineers don’t seem to appreciate the fact that standardization has a value beyond the ‘value-added’ by tweaking a standard up into a new level of incompatibility.

Common sense…isn’t.

CR
March 31, 2007 at 3:52 pm | Reply

Knudsen,

Yep, you’re missing the point. Powered USB hubs permit _each_ _port_ of a USB hub to deliver 500mA @ 5V to connected devices. With an unpowered hub you’re limited to a _shared_ 500mA for all devices, minus the power used by the hub its self.

A powered hub won’t let you power (eg) a 3.5″ external RAID enclosure or a professional scanner, because the device still needs more than 2.5W. However, a powered hub _will_ let you power, say, four external 2.5″ USB bus powered hard disks, one per port. With an unpowered hub that’s just not going to happen as the combined draw of the devices will be WAY more than 2.5W (closer to 10W).

Powered USB is designed to handle genuinely high power demands like this, where you’d normally have to plug in yet another annoying power brick.

Make sense?

Carey
March 31, 2007 at 3:50 pm | Reply

There’s other things to consider too. The amount of electrical “bleed” from peripherals is staggering. Even though your scanner is turned off, it still has power flowing to it from the wall wart. With PUSB, the drivers or even OS can turn off the flow of power to the device when it’s unwanted.

Paul Crowley
March 31, 2007 at 3:11 pm | Reply

Having one large power supply in a desktop computer is not really optimal unless it is very limited in what can be powered. Having to have a power supply in every desktop that can supply 400 or 500 watts on USB for drives, printers and so on would be a significant added expense. Especially for people that are paying for that additional capacity without using it.

Having a bigger power brick for a notebook is a disaster. The last thing that is needed is bigger and heavier gear to carry around.

Today’s individual power supplies for individual devices perhaps not optimal but it eliminates the issue of having one mega-supply for everything. Even putting a 12V power supply into a power strip just changes how the supply plugs in.

There is also the single-point-of-failure argument. Having one power supply that smokes out does not mean the printer is no longer usable – it means the computer is no longer usable.

bluechillies
March 31, 2007 at 2:35 pm | Reply

Why not just go with the power strip ideal and include all on the strip to work at different levels. I know I would buy one if it’s was labeled and easy to use.

Hope Leman
March 31, 2007 at 2:00 pm | Reply

Would the men of the IT world pleasssse stop using the “mother” or “grandmother” analogy when they want to suggest stupidity or technophobia? How about, “Your idiot of a father…” for once?

Old Timer
March 31, 2007 at 1:50 pm | Reply

While their points are valid, I think readers would appreciate these articles more by viewing them with a broader perspective.

I’ve been employed as a tech since a time before PC’s (& Apples). Although consumers will benefit from standardization, business has the most to gain–interchangeable peripherals, simplified tech support, simplified purchasing, less fire danger (lower voltage devices), lower cost devices, and so on.

My only disagreement is the “elimination” of Firewire. If it is a better standard, then it should prevail. I’m still reminded of the inferior VHS (Windows too?) coming out on top because of marketing success, not technical superiority.

I say Great Ideas! Let me know when they’re available so I can be the smart guy in my corporation!

anti-Environmentalist
March 31, 2007 at 1:40 pm | Reply

Actually I’m not an anti-environmentalist, I just want to point out that Environmentalist makes no sense in his comments. The electricity is NEEDED and thus will have to come from somewhere whether or not USB provides it. And actually, those bricks that usually provide it use inefficient linear power supplies based on large transformers – and they waste most of the voltage conversion making heat. By contrast, power from Powered USB comes from far more efficient switching power supplies, which waste much less energy. So powered USB ends up wasting less electricity powering the devices we’re all going to have anyway.

warren
March 31, 2007 at 1:13 pm | Reply

Either “environmentalist” is a troll, or a moron. I think he’s a troll.

W

Omnifarious
March 31, 2007 at 1:08 pm | Reply

>>> Powered USB is the last thing we need. Computers are already using too much power. The environmental impact from using all that electricity will be devastating.

Wow. That is an impressively dumb and ill-thought-out comment. First, all those devices are using that power right now. But, most of the time a whole bunch of power is being wasted as heat in a little transformer block.

Secondly, as someone else pointed out, this can allow programmatic control over power consumption. This will allow less power to be used overall because devices that aren’t being actively used can be shut off.

A knee-jerk “it’s power, it must be bad” response is the kind of thing that gives environmentalists a bad name and makes me suspect you’re just a troll.

Cillian
March 31, 2007 at 1:00 pm | Reply

Would it not be possible to have one socket to rule them all? What I’m thinking is, powered USB has one socket with pins specified for every power level supported. Then you have just lots of these. A device like a keyboard which needs low power only has pins for the low power stuff, but a high power device like a screen has the extra pins for a higher powered socket. Now here’s the clever part – If a device like a laptop doesn’t want to send out high power because it just isn’t available internally, then it has the holes for low power devices but no hole where the high power pins go. This means low power devices can plug into low and high power sockets, high power devices only plug in high power sockets, etc… This means you only need lots of one type of PUSB socket on the host device – you just include the highest power socket you want to support.

I would absolutely love PUSB so I can take my laptop down the garden and still use high power devices. As for the comment that this encourages power waste – that makes *no* sense. Taking power from USB doesn’t waste anymore than taking it straight from the wall – probably less.

Will Godfrey
March 31, 2007 at 12:59 pm | Reply

Having seen the results of ‘user intervention’ I can’t say I’m overly keen on all that power available in cheap flimsy connecting leads. Best upgrade your fire insurance 🙁

Luis Alejandro Masanti
March 31, 2007 at 12:55 pm | Reply

PUSB maybe is following USB tradition: If actual 1.1/2.0 specs have rectangular and square plugs, why not rectangular/square/round/circular/triangular/star-shaped…?

Firewire 400 and USB 1.0 where developed by the same time (although for different purposes). Why FW was so versatil and USB so fixated?

Oscar the Crouch
March 31, 2007 at 12:46 pm | Reply

>>Powered USB is the last thing we need. Computers are already using too much power. The environmental impact from using all that electricity will be devastating.

While it is true that todays computers do use a lot of power, having peripherals powered directly from the CPU could substantially decrease the amount of power used by these devices. For instance, my wireless mouse currently is connected to the computer via USB 2.0 and has an external power source. While in the cradle, the mouse is charging all of the time. By using PUSB, not only would I have one less cable to deal with, my charger and mouse could both be shut down, or scaled back to a smaller drip charge, when the mouse was completely charged. Additionally, how many people do you know who leave there printer on all of the time. With PUSB, the printer could be shut down when the computer goes to sleep. The environmental footprint of our electronics would actually be less with PUSB

Davo
March 31, 2007 at 12:41 pm | Reply

>> Powered USB is the last thing we need. Computers are already using too much power.
>> The environmental impact from using all that electricity will be devastating.

Environmentalist – only if people start running more devices in their homes will there be any increase in energy usage. Adding Powered USB ports to a computer doesn’t “use” any more electricity than adding a new mains socket under the stairs. There’s no energy difference between buying a regular USB printer and plugging it into the mains power or buying a Powered USB printer and plugging it into the computer.

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