My laptop’s IP is 192.168.2.4
My desktop’s IP is 192.168.2.2
My router’s IP is 192.168.2.1

So, the work around seems to be this…

On the laptop, with eth0 already up:
ifconfig firewire0 up 192.168.2.4
route del -net 192.168.2.0 netmask 255.255.255.0 dev firewire0
route add -host 192.168.2.2 dev firewire0
iptables -F
iptables -P FORWARD ACCEPT
echo 1 > /proc/sys/net/ipv4/conf/all/forwarding


On the desktop:
ifconfig firewire0 up 192.168.2.2
route add default gw 192.168.2.1

To make this permanent, you would edit /etc/networking/interfaces like this…

On the laptop:
auto eth0
iface eth0 inet static
address 192.168.2.4
netmask 255.255.255.0
broadcast 192.168.2.255
gateway 192.168.2.1
post-up ifconfig firewire0 down
post-up ifconfig firewire0 up 192.168.2.4
post-up route del -net 192.168.2.0 netmask 255.255.255.0 dev firewire0
post-up route add -host 192.168.2.2 dev firewire0
post-up iptables -F
post-up iptables -P FORWARD ACCEPT
post-up echo 1 > /proc/sys/net/ipv4/conf/all/forwarding

On the desktop:
auto eth0
iface firewire0 inet static
address 192.168.2.2
netmask 255.255.255.0
broadcast 192.168.2.255
gateway 192.168.2.1


I originally planned the Powered USB article as two parts, one explaining why USB took off, and another explaining why USB isn’t the best solution because it can’t power large devices plus why Powered USB isn’t the greatest solution either because it isn’t in consumer electronics yet and has the different plugs for different voltages issue as well.

What I didn’t plan on was all the Firewire fans popping up and saying I was wrong for pushing a Powered USB/USB 3 combo. For the record, I’m also a Firewire fan but haven’t gone to the fanatical levels some people have. Part 3 is for you guys.

Note: I originally intended for USB 3 and New Powered USB to be separate standards, allowing devices to use one or both (but New Powered USB would require USB 3 to negotiate for power usage). The way I will describe this possible future USB 3 in part 3 is basically folding the new data features into the New Powered USB part of the plug to remain compatible with USB 2 hosts/devices/hubs.

The problem with traditional USB is because:

1. It’s slow.
2. Can’t allow devices to perform the DMA-like transfer method Firewire does¹.
3. It’s slow.
4. Uses polling to transfer data, thus eats CPU time like mad.
5. It’s slow.
6. Future USB specifications cannot perform interrupts to signal for the host to acquire new data, and can only use polling.
7. It’s slow.

Even with these problems, I can still say future USB products look promising because the reason I chose a formalized New Powered USB specification combined with a future USB 3 specification is because almost everyone has USB ports, and it has become the ubiquitous peripheral port on all sorts of devices. Not all devices come in Firewire versions, and not all computers have Firewire ports.

The Proposed USB 3.0 Specification Checklist

USB is being held back by the fact it can’t perform interrupts. USB 3 cannot just add it in the normal USB host interface stack: USB was never designed for it, and you can’t just add it as a feature that can be negotiated between host and client. It wouldn’t work.

However, what would work is adding a second new interface that is slaved to the first: allow USB 3 devices to negotiate to use this new second interface, and allow the second interface to work independently of the original legacy interface. This secondary interface could not only perform interrupts, but be able to do anything USB 2 is missing.

There are two reasons you need the independency: one, USB 3 hubs need to be able to transfer data from both legacy USB 2 devices and USB 3 devices (all the USB 2 data will be going across the legacy bus independently of USB 3 data); and two, USB 3 devices will no longer be using the legacy interface for any data transferring once the negotiation is complete. The legacy interface will act as an out-of-band interface for non-important USB-related traffic (such as for re-negotiation, or for negotiation of/for USB 3 clients plugged into USB 3 hubs, or for just telling the host it’s still plugged in).

This second interface, since it is now independent, can virtually use any protocol it wishes. If the USB Working Group so decided, they could run Firewire unmodified over this second interface. The possibilities are endless. Most likely, it’d be some USB-IF designed Firewire clone.

There is something else I need to add to this checklist: USB 2 legacy communicaiton with USB 3 hosts and clients. As I said, USB 3 devices would have to negotiate to use the secondary interface, but what happens if either the host, client, or hub rejects this?

USB 3 clients will have to be able to do their work as standard USB 2 devices. Obviously, high bandwidth applications would run a lot slower, DV devices might not be able to be used in real-time, and Powered USB power features couldn’t be negotiated for (most likely the USB 2 client/host/hub would be using a normal USB plug in the first place). USB 3 hubs connected to USB 2 hosts would have to reject USB 3 connections as well and tell any USB 3 clients connected to the hub to run in USB 2 mode.

More pins doesn’t exactly mean a new data connector

Of course, this second interface requires more pins, yet has to stay compatible with the old USB plug. Frankly, doing what Firewire 800 did (adding a 9-pin socket/plug that requires an adapter to plug 6-pin devices/plug into 6-pin hosts) is possibly a bad idea as it requires people to have yet another small part that is easy to lose. Adapter dongles and short adapter cables suck.

The idea I’ve been playing around with is to attach these new pins to the consumer-friendly New Powered USB plug I hinted at in part 2 of this article. Just add, say, four or six pins to the outside of the plug’s inner column like how Type B USB plugs work now, while leaving the power pins on the inside of the column like the are in the original design. Remember, these pins are for data only, all three Firewire plug designs only use two pairs for data.

However the plug actually gets designed, I don’t care; it just has to be done in a way that doesn’t interfere with the legacy USB plug. Putting the new data pins in the New Powered USB half of the connector seems to be the ideal way of solving this without going Firewire’s route.

So thats it? Just clone Firewire’s features?

The two main things that Firewire has over USB at this time is the fact that Firewire devices can use interrupts (which, if you haven’t figured it out yet, is causing Firewire 400 to actually hit 400mbps, and USB2 to hit about half of it’s 480mbps), and the fact that Firewire can power devices that are more power hungy, is why, in theory, Firewire is the better bus.

But as I said before, USB is the defacto standard for peripheral communication, and Firewire is in far fewer devices, and some computers don’t even have Firewire ports. As much as I’d like to see Firewire kill USB, it is not going to happen any time soon.

So yes, what I’m saying is USB 3′s secondary interface has to either copy Firewire’s features or use Firewire directly. Firewire can’t kill USB, USB is having a hard time killing Firewire, so the only way I see this problem being solved is by allowing USB 3 to do everything Firewire does now while still remaining compatible with USB 2 devices and hosts.

_{[1]: On some platforms it really does turn into a PCI DMA and allows you to read/write part or all of the system memory, such as for live debugging purposes on another machine. I’d like to see this on USB 3 as well.}

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.