Why Powered USB Is Going to Fail

An anonymous reader writes "Patrick McFarland, famous Free Software Magazine author, has written a two part article about why Powered USB is not taking off at home. (part 2 is also available) He includes a lengthy history on why USB took off in the first place, and then continues on to explain what we gain by allowing Powered USB to power all our devices."

Comments

I agree

[MrNaz]

Agreed.I've never been a big fan of USB. The concept is fantastic, a unified connector that links just about any device to any other and can charge them is a great idea. However I am still bitter the Firewire lost out. It has more bandwidth, has sturdier connectors, and can deliver far more power. Being able to just plug one cable to power and link a hard drive would be great, I have one of those external IDE enclosures, and having *another* power brick is just silly.

Being able to charge high draw devices through Firewire would rock. Powering my laptop from my PC would be great, especially if it will be syncing files at the same time, allowing me to leave the power brick in my laptop case and not have to get it out after getting home.

In my eagerness to get this post in first, I didn't read the article before I started typing. He says it all the same way I would. So to all of you who haven't RTFA'd, do it to find out the rest of this comment's points. Now lets see if I can still get this in first...

Re:I agree

[DeathFromSomewhere]

Try a 2 1/2" drive instead of a 3 1/2". The smaller drives don't require a separate 12V supply and are easily powered by USB.

Re:I agree

[diablo-d3]

Hi, I'm the guy who wrote the article in question. Yeah, I had laptops-charging-while-syncing in mind as well when I wrote the article, its only a step up from PDAs who charge while syncing (which already is done via normal USB on some PDAs).

I'm a fan of Firewire as well, which is mainly why I wrote this article in the first place. Powered USB handles all the power issues (except for the flaws I noted in my article), and a future USB 3.0 revision will catch USB up to Firewire 800 over 9 pin cables (as opposed to the new over-CAT5 and over-Optical versions that are really for special use applications and completely outside the realm of desktop computing), so I just don't see why they don't clean up Powered USB and either integrate it into USB 3.0, or release it as a more official optional extension.

USB may have killed Firewire, but that doesn't mean USB is ready to replace it quite yet; the fact Firewire 800 was even released, and supported on non-Apple devices pretty much proves that.

Re:I agree

[repvik]

Bzzzt! Wrong. There's no guarantee that 2.5" drives do not require more than 0.5A @ 5V. I've got four drives in front of me, and three of them require 0.7A.

Not only that, but the 2.5" drives are more expensive, slower, and has way less storage capacity.

Re:I agree

[Ruie]

Agreed.I've never been a big fan of USB. The concept is fantastic, a unified connector that links just about any device to any other and can charge them is a great idea. However I am still bitter the Firewire lost out. It has more bandwidth, has sturdier connectors, and can deliver far more power. Being able to just plug one cable to power and link a hard drive would be great, I have one of those external IDE enclosures, and having *another* power brick is just silly.

One thing the author of the article missed is the original purpose of parallel and joystick ports. They were called "parallel digital input/output port" and "scientific port". The parallel port was meant for general purpose digital I/O (so you control relays or tell whether a contact is closed or not) and the scientific port could be used to connect thermocouples for example.

These were "starter" ports that made the computer useful in the lab or in the factory without purchasing additional components. Nowadays a special expansion card or external device are necessary to get back the same capability. The cheapest are around $100, but this quickly ratchets up to $1000 and more for anything capable.

One thing to keep in mind is that the original IBM PC (which was before XT and before AT) had a fairly slow processor (6 or 8 Mhz ? - can't recall) and the audio-range sampling rates of parallel port and joystick port matched them well. Nowadays we have Ghz cpus, but anything that captures faster than 100 Mhz is expensive - with Ghz cards costing more than the cost of the computer.

Re:I agree

[that this is not und]

At Frys they now sell a USB to IDE drive adaptor that is a 'molded cable' adaptor for attaching an 'out of the case' 2-1/2" Hard Drive to your machine. Very handy for transferring data from drives that have been pulled from a laptop, also good for 'injecting' stuff onto drives you're going to plug back into a laptop. The adaptor nicely powers a typical 2-1/2" laptop without any difficulty.

It's the same 'guts' as used in those cheap aluminum USB 'laptop drive' external housings, which also get their power from the USB with no difficulty.

Re:I agree

[that this is not und]

Nowadays a special expansion card or external device are necessary to get back the same capability. The cheapest are around $100

You're correct, but to be fair in comparision, back when those ports were popular on the IBM-PC, the parallel, serial, and joystick ports were themselves expensive add-on cards.

The PC and PC-XT had NO built in I/O. You had to plug in EVERYTHING as expansion cards, includng floppy controller card, hd controller card, serial card, parallel (which you could get built on with the MDA monochrome text-only video card), game port card, video card. None of these were built in 'on the motherboard.' On the original PC it wasn't hard to tie up all five expansion slots, since you also didn't get 640K on the motherboard, so had to plug extra RAM in _brace_yourself_ an expansion card in other I/O slot.

Thus the rise of the 'AST Six-Pack' and other multifuntion cards, which gave you seral/parallel/memory/realtime-clock/etc. all on one card (a card that cost about what people pay now for a whole system at Wal-Mart.)

Re:I agree

[jwdav]

I think you have it backwards, unless you have a PC or FireWire Card that doesn't support bus master. It is not uncommon to find marginal FireWire support on PC's, but most consumer & pro electronics, as well as all Apple products offer full Firewire support.

USB requires a host CPU; FireWire does not.

FireWire uses a "Peer-to-Peer" architecture in which the peripherals are intelligent and can negotiate bus conflicts to determine which device can best control a data transfer

USB 2.0 uses a "Master-Slave" architecture in which the computer handles all arbitration functions and dictates data flow to, from and between the attached peripherals (adding additional system overhead and resulting in slower, less-efficient data flow control)

USB 2.0

1.5 Mbit/s 12Mbit/s 480Mbit/s supported.
USB controller is required to control the bus and data transfer.
Cable up to 5 m.
Up to 127 devices supported.
Power supply to external devices is 500 mA/5V (max).
Full compatibility with USB 1.1 devices.

FireWire (IEEE1394)

100 Mbit/s to 800Mbit/s supported.
Works without control, devices communicate peer-to-peer.
Cable up to 4.5 m.
Up to 63 devices supported.
Power supply to external devices is 1.25A/12V (max.).

Re:I agree

[jelle]

USB always makes me struggle which way to put the connector in. Firewire is a little better, but still, you'd think that the people who make connectors would be able to come up with either a connector that makes it obvious which way it goes in, or one where it doesn't matter how it goes in.

We're still in the 'connector stone-age' if you ask me...

USB needs to add more firewire like stuff

[Joe The Dragon]

like offloading work from the cpu as the older and slow fire wire 400 bus is faster then the usb 2 bus and it can be used to link 2 systems together with out a special cable.

Re:USB needs to add more firewire like stuff

[Hal_Porter]

like offloading work from the cpu as the older and slower fire wire 400 bus is faster then the usb 2 bus and it can be used to link 2 systems together with out a special cable

I don't think USB will ever support peer to peer. USB 1.0 was designed to have a smart host and dumb devices, to make sure that low end Asian manufacturers could make mice and keyboards with a couple of man-weeks of labour, probably only a few man hours once they get up to speed. Later on people started to use it for storage, and USB 2.0 was needed to up the speed. But it was never designed to do firewire type things like peer to peer networking, because Intel thought that Firewire would always do those. Theoretically, you could have two USB OTG hosts linked together, one as "device" and one as "host", but support for OTG is non existant on desktops.

But remember that USB is popular because every PC has it, and there are loads of sub $30 USB peripherals. If it had started off like Firewire, that wouldn't have happened.

I sincerely hope powered USB fails

[Thagg]

I don't feel that computer designers should really have to think about some peripheral device sucking 50 watts out of a connection on the motherboard. If you want power, get a cord. If you want portable power, bring a battery. Just having one fewer cable on a desk is not a problem worth solving this way.

Laptops, for instance, are designed around very limited power budgets. If you plug a 1000 watt USB hair dryer into it, how long are the batteries going to last?

A solution I would be in favor of is building lower power peripherals. Building 500 GB flash hard-drive replacements than run on half-a-watt should be possible in a couple of years. Building very low power OLED displays should be possible. Building low-power devices is something that is a win in every possible way, and should be encouraged -- the USB power limitation is a great way to stimulate this!

That said, I'm really sorry I passed up the USB-powered heated typing gloves I saw in Shinjuku last fall...

Thad Beier

Re:I sincerely hope powered USB fails

[swillden]

I don't feel that computer designers should really have to think about some peripheral device sucking 50 watts out of a connection on the motherboard.

Why not? Sure it's another factor in motherboard design, but as long as the USB peripheral and the controller can negotiate the power demands, then it's easy enough to make sure it's not going to burn anything out. If a device would draw more power than the mobo would supply, the controller simply wouldn't power it. That would make USB-deliverable power another feature by which to compare mobos.

Just having one fewer cable on a desk is not a problem worth solving this way.

I disagree. Perhaps I would agree if it were only one cable, but it's not. It's often four or five cables. My desktop, for example, has two printers, a scanner, speakers and a monitor, plus the CPU, so that's six power cables and six data cables (including the network). Worse, the six power cables require two power strips (because the wall warts cover more than one outlet on a typical power strip), so there are an additional two cables, for a total of 14 cables under my desk, for that one computer. Powered USB, if done right, could conceivably eliminate both power strips and all but one of the power cables, so instead of 14 cables, I'd have seven. Even better, the routing of the seven would be cleaner, since all of the peripheral cables connect to the computer and the compute is the only one that connects to the wall. That's well worth doing.

Laptops, for instance, are designed around very limited power budgets. If you plug a 1000 watt USB hair dryer into it, how long are the batteries going to last?

Not long, of course, but if I want to do that, and if the laptop can deliver the juice (unlikely in your example, but we could construct another that was more feasible), why shouldn't I be able to? They're my batteries and the power in them is mine to spend as I please.

A solution I would be in favor of is building lower power peripherals. Building 500 GB flash hard-drive replacements than run on half-a-watt should be possible in a couple of years. Building very low power OLED displays should be possible. Building low-power devices is something that is a win in every possible way, and should be encouraged -- the USB power limitation is a great way to stimulate this!

Given the increasing move to portables and the apparently-insurmountable limitations of batteries, I think that problem takes care of itself. Low-power USB-powered devices would have an inherent mobility advantage that would drive their sales over hungrier devices. They'd also be cooler and quieter, which also tends to please buyers. There's no reason to impose an artificial barrier which makes classes of devices that can't quite reach the 0.5A mark completely infeasible.

Re:I sincerely hope powered USB fails

[kabz]

I can turn my laptop into a portable wireless hairdryer by running warcraft.

USB Power Strips as notebook power supplies

[cnaumann]

I love the idea of those USB power strips. Imagine being able to power your notebook off of one! That could end the different power brick for every notebook mess.

On USB 2.0 vs. FireWire400/800: I know that this subject as been beat to death, but anyway... Higher speed are always nice, but I am not often limited by the bus speed. What I LOVE about USB is that the specification is open. Anyone can download it. You can build your own USB gizmos in your basement; no large investment is required. There are plenty of chips that support USB available in small quantities (like 1 or 2). You can even make USB look just like a serial port, making said gizmos compatable with LABView with no driver fuss. Try that with FireWire! Now if I could make all my little lab gizmos powered off the USB bus as well, heck, I might never go home.

I know FireWire is popular for video transfer, but isn't that what DVI is for? For data transfer, you don't have to run DVI in real time, and you can run 3.9 Gbits/sec over DVI today.

Powered USB has a short shelf life

[goombah99]

Powered WiFI is going to take over!

Re:how to tell a girl you want to eat here out?

[Hal_Porter]

theres this girl I like and I really want to eat her out. I could spend hours pleasuring her. How do I ask her?

Register for callbacks on device enumeration.

Once she has enumerated, check her device descriptor bDeviceClass for class USB_HUMAN and bDeviceSubClass for HETEROSEXUAL_WOMAN. These steps are very important, do not omit them. If these are zeros in the Device Descriptor, iterate through all the Interface Descriptors. Note, if there is more than one Interface Descriptor, it may be best to skip the device.

Now send a class request, SET_FEATURE ( HUMAN_ORAL_SEX ). If she doesn't stall the request, you are good to go. Some targets have a bug where the request are stalled incorrectly a few times. In this case, you should retry a few times, but not too many, unless BUILD_OPTION_EMO_LOSER is defined in which case you should retry an unlimited number of times until the OS bugchecks. Actually, if that is defined, you can skip the class and subclass post enumeration checks too.

Why Device Industry doesn't want Powered USB...

[Glasswire]

... to succeed: For the same reason there is are NO standards for external power bricks for laptops/printers/scanners/hubs etc. Because there is a high margin add-on market from manufacturers to replace proprietary power devices (when lost) with expensive branded units which are probably about 5x to 10x the cost of what generic units would if there was a some common defined types (V/ma/connector-types) which would be universal. A move to efficent USB power would undercut this business in the same way, so the only standard that will be agreed upon will be an unworkable one. Firewire never replaced USB because it had licence encumberences (cost more to use), alas.

Wireless

[shmlco]

"Perhaps I would agree if it were only one cable, but it's not. It's often four or five cables. My desktop, for example, has two printers, a scanner, speakers and a monitor, plus the CPU, so that's six power cables and six data cables (including the network)"

So? Work smarter. I have a 17" Apple MacBook Pro on my desk and it has exactly ONE cable connected to it: the MagSafe power connector.

The mouse I use (when I use one) is Bluetooth. My printer and speakers are plugged into an AirPort Express across the room. A 500GB hard drive and the big HP color laser are plugged into an Extreme in the next room, which is where the DSL line comes in and besides, it's quieter that way. Backups to the HD, while slower, are scheduled and occur in the background, so who cares how fast they happen? The network is obviously wireless, and 802.11n due to the Extreme.

I have a USB-powered Canon scanner, and I plug it in when I need to scan something (rare).

The Apple AirPort Extreme and Express are great options, and work on Macs and PCs. I think Belkin also has a wireless USB hub for PCs.

In short, if you have too many wires, then get rid of them.

Re:Wireless

[swillden]

So? Work smarter. I have a 17" Apple MacBook Pro on my desk and it has exactly ONE cable connected to it: the MagSafe power connector.

Right, so you get rid of some cables at the expense of accepting a small, low-resolution screen with limited contrast and small, slow data storage. Not a good tradeoff for me, at least (as compared to the 23" 1920x1440 CRT and striped 320 GiB 3Gbps SATA drives on my desktop).

If a laptop can accomodate your computing needs and fits into your budget, then certainly it's a good way to eliminate (some) cables.

My printer and speakers are plugged into an AirPort Express across the room.

Which means you haven't gotten rid of any of those power cables (or the power strip, most likely), you've just moved them away from your desk. Not a bad thing, certainly, but not as good as eliminating them. Now imagine how clean it would be if the AirPort Express supported powered USB devices, and your external drive and printer ran from that.

Also, I should point out that my LAN is GigE for a reason. I move a lot of big files around and even 100BaseT is annoyingly slow (I can't saturate the GigE, but I get transfer rates about 3x as fast as 100BaseT could handle). I have an 802.11g WiFi network, but even my laptop is plugged into the GigE when I'm at my desk, because WiFi is just too slow when you need to move data.

I have a USB-powered Canon scanner, and I plug it in when I need to scan something (rare).

So there are two more cables on your desk, though one of them isn't typically attached to your computer. Again, powered USB would eliminate one of them.

The Apple AirPort Extreme and Express are great options, and work on Macs and PCs. I think Belkin also has a wireless USB hub for PCs.

Certainly, if they work for you and if you don't mind paying for them. Also, I don't think they work for Linux, except for the music playing option (I'd like to be wrong here!). They don't, however, really remove the need for cables so much as allow you to spread the cables around a little more. That's not bad, but it's not as good as eliminating them.

Re:I disagree

[Stewie241]

Agreed... but I think a balance is necessary - increased power efficiency, but there are some devices and applications that need more power than the standard allows.

A typo? I have a 17" MacBook Pro that supports FW800 just fine.
Not a typo... poster was only referring to the fact that many PC manufacturers don't include add-ons that most people never use. Mac's having this hardware is the norm, for PCs, it is not. For a PC to have it, it means that it is at least gaining some common use.

Other Reasons

[Apreche]

There are some other reasons why USB was adopted so widely. First off, it was hotplug. All the other ports like PS/2, Serial and Paralell required you to restart your computer if you wanted to change what was plugged in. USB finally allowed you to change devices while the computer was on. Imagine iPods or thumb drives if USB was not hotplug!

The other advantage of USB was that the plug is simple. It's just a rectangle that goes in a rectangular hole. You can't put it in backwards. There are no screws to hold it in. It's very approachable. Unlike serial, paralell or game ports, which look like they belong in the back of the computer and not the front, USBs are safe to put on the front of just about anything. The design of the port itself invites people to use it, rather than scare them away.

These are the other reasons USB is awesome, and also yet more reasons why Powered USB will not work. Adding any sort of extra plug will just make USB scary again. The only way I see powered USB working is if you find a way to transmit that power with a connector that is identical to the existing USB port.