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The whys and wherefores of a shrunken Dock connector (Updated)


Rumours that Apple would be switching the next iPhone to a new, smaller connector than the venerable 30-pin Dock connector go back a long way -- as far as iMore's writeup from February. They resurfaced recently following a claim by TUAW's sister site TechCrunch that a source had confirmed this was definitely happening.

Now, I'm not one to put too much stead in rumors -- the Apple rumormill is too fast, frantic, and frequently fictional for that (thanks for the lulz, Digitimes!). But I do believe that if you apply some common sense, and if you see a rumor pop up multiple times, well, it often suggests there really is something afoot. So let's assume there's some substance to the rumors, the spy shots of leaked case pieces are real, and Apple is at least prototyping (if not releasing) a smaller Dock connector. Does this make any kind of objective sense? What will it mean for users? Let's see what we can puzzle out.

Before we begin -- this article contains some supposition on my part about exactly how some existing devices work when plugged into the Dock connector. Apple's official documentation is all locked up behind ironclad NDAs, and none of the OEMs we reached out to were willing to comment off-the-record on the fine details of making peripherals for iPods and iPhones.

Update: after publication of my original article, I was contacted by Brian Klug of Anandtech. He shared with me this picture of an internal iPhone component board, which clearly shows a smaller Dock connector and a bottom-mounted headphone jack. The board picture pre-dates the case leak shown in the picture above, so taken together, each component leak corroborates the other. This makes it more likely the rumors are genuine.

The argument for shrinking the Dock connector

It's pretty clear why Apple would want to do this: to save space inside the device, which it could then fill with goodies like more battery or LTE chips or a stash of powdered unicorn horn. There's an obvious counter argument, however. Surely the Dock connector isn't that big? Can Apple really save enough space to be worth the time and effort?

Well, let's ponder this for a moment, with the aid of some admittedly hand-wavey mathematics. If you (as I just did) take a ruler to the plug part of a Dock connector, you'll find it measures 21 mm ח 2 mm ח 6 mm. (Yes, gentle reader, I used a ruler rather than a micrometer. I'm afraid TUAW's budget doesn't push to precision engineering instrumentation. I also offer no apology at all for using millimetres, which are so very clearly better than the arcane and baffling "sixteenths of an inch" that I cannot begin to describe how ridiculous the Olde World units look to those of us in the metric haven of the actual Olde World.)

Anyway, digression aside, that works out to 252 cubic millimetres, and that's just the volume of the part of the plug that goes into the phone. There's additional space taken up within the handset, of course, by the surrounding metal shield, connection points, and so forth. Hang on to that number for a second.

Now, consider the micro SIM that Apple uses in all current iPhone and iPad models. It's 15 mm ח 12 mm × 0.76 mm -- 135 cubic millimetres. The little tray it sits in adds some size though; on my iPhone 4, that's about 19 mm ח 14 mm ח 1 mm, or 266 cubic millimetres.

Famously, of course, the iPhone 4 was an early device to adopt micro-SIMs; before that, Apple used mini-SIMs, which are about twice the volume (25 mm ח 15 mm ח 0.76 mm). The switch to micro-SIMs wasn't without pain for consumers. I bought my iPhone 4 on launch day, and although I could have had a new SIM with a new contract that day, I couldn't convince my carrier to send me a micro-SIM attached to my existing account for a few days later. Similarly, there were no pre-pay micro-SIMs to be had for several weeks.

By foisting that inconvenience on me, Apple saved something like 300 cubic millimetres, give or take. Again, I am fudging slightly to account for the extra room taken up within the phone by the mechanism the drawer slides into, but for the general point I am making I only need approximate figures.

That wasn't enough, though, but it's OK -- Apple can rebuild it. Smaller. Sleeker. Even easier to misplace. Yes, it's the nano-SIM, coming soon to a phone near you. It's taken Apple since May 2011 to get ETSI to approve the new standard, and it took some horse trading with Nokia, but approve it it has. The new standard is 12.3 mm ח 8.8 mm ח 0.67 mm -- or 72.5 cubic millimetres.

So, let's recap. We saw Apple cause consumers some minor pain by switching to an as-yet-unused standard, the micro SIM, to save about 300 cubic millimetres. We've seen Apple go through a year-long standards fight to shave about another 100 cubic millmetres away (including the space saved with a smaller drawer). Clearly, Apple believes every single scrap of space inside an iPhone is worth working for.

Now let's look at that Dock connector again: 252 cubic millimetres, plus the space for the metal housing within the phone that it connects to. If Apple was prepared to fight as hard as it has to save space on the SIM card, I think it's credible that the potential savings from a smaller Dock connector are also on its roadmap.

Looking at the size of the rumored new connector, it looks like it's around a third the size of the current Dock plug. That implies a saving of something like 160 cubic millimetres from the new design.

How could Apple do it?

If you glance over the Dock connector pinout, you'll see the 30 pins in the existing connector break down as follows:

  • 5 pins for miscelleneous ground and reserved wires.
  • 9 pins for AV out, in various formats (line-level audio, composite, S-Video, video formats).
  • 4 pins for the iPod accessory connectivity (e.g. for add-ons like Nike+, the TomTom standalone GPS, iPad Camera Connection Kit, and so on.) Includes a 3.3 V power line, so the accessory doesn't need its own battery.
  • 8 pins originally used for Firewire, now presumably unused on newer devices.
  • 4 pins for the USB connection (for both syncing and charging).

It's easy to see that Apple could slim this down to the rumoured 19-pin connector without causing significant loss of functionality, simply by ditching the long-deprecated Firewire and then either some of the older video-out formats like composite or some of the "reserved for future use" connections.

Then, because the new connector would be electrically compatible with the old one, Apple could supply cheap mechanical adaptors that would allow any older Dock cable to accessory to work with the new iPhone.

Standards, standards, everywhere, but not a port to use

One criticism often levelled at Apple's industrial design is that it has never adopted the industry standard micro-USB for the iPhone. If Apple is going to change ports, wouldn't it be a good idea to change to the same one everyone else is using?

Let's examine the arguments in favour, first of all. Micro-USB is inarguably popular; practically every other mobile device now uses it, including other smartphones, Kindles and every iPhone battery case I've ever handled. It can do charging and syncing, and cables are cheap and ubiquitous. It's good for users, who can purchase accessories cheaply and share them between devices; and the reuse angle mean it's also good for the environment.

Update: as several commenters have pointed out, the environmental angle drove the 2010 decision by the EU to mandate that all chargers should be universal, following the voluntary trade agreement by 14 cellphone manufacturers in 2009. However, Apple is already compliant with this ruling. Note that the EU's FAQ explicitly states that "[t]he agreement allows for the use of an adaptor", and Apple have just the thing. As long as Apple issued a similar adaptor for any micro Dock standard -- and there's no reason why it couldn't -- then there would continue to be no need to put micro-USB on the device itself.

Why might Apple want to avoid micro-USB? Because charge and sync is about all micro-USB can do, on the face of it; the accessory support, line-level audio out, and video out features the current-day Dock connector sports aren't possible down a four-wire connector. There's a nascent standard called Mobile High-definition Link which can be used for video out but it's rather clumsy, involving three-tailed pass-through cables on existing Android phones. Note that, unlike with Apple's AV connector, the MHL adaptor cannot draw power from the handset and so has to be plugged into a USB charger to function.

It's possible that Apple could address this by using a software layer to multiplex different data types on top of the USB connection, but that would require rather more complex controllers on either side to unpick the data again and do something sensible with it. In fact, something similar is already in place -- several car stereos, for example, connect to the Dock port via a USB cable, then retrieve music, track data, and other information from it. Multiplexing digital 1080p video streams is a harder problem, however, and even if Apple solves it, it still couldn't maintain backwards compatibility with existing Dock-equipped accessories.

Why not Thunderbolt?

Thunderbolt is a sophisticated interface that achieves never-seen-before bus speeds; 20 times faster than USB2, twice as fast as USB3, three times faster than eSATA. To manage that, no expense was spared on any aspect of the design, which is why the cables alone cost $50, with even more money spent on the chips inside the computer to make all those bits whizz around. Meanwhile, the NAND flash memory Apple uses for the iPhone is about a third as fast as USB2's maximum speed, or less than 2% of Thunderbolt's capacity. Adding Thunderbolt to an iOS device needlessly and greatly inflates the cost of production for absolutely no practical benefit. It's nonsense.

The outlook for gadgets

So, yes, that vexing backwards compatibility angle.

There's no escaping the fact that a new Dock connector will, on the face of it, immediately invalidate every single cable, add-on, and charger you own. There's no escaping the fact that this sucks, either.

For cables, at least we will (presumably) quickly be able to get cheap ones from eBay to replace all our existing Dock USB cables. That's assuming Apple doesn't do anything funky like adopt a standard that is rigidly patent-protected like MagSafe, anyway -- let's all sincerely offer a silent prayer of hope that we won't have to buy every microDock cable from Apple for $19 a pop for all eternity. And of course, chargers that have a USB port will still work if we exchange the cable.

For peripherals the picture looks less rosy. The best we can hope for is that the rumours are correct and we get a 19-pin connector which is electrically compatible with the existing one, then at least Apple could throw us a bone, in the form of a physical dongle, not unlike the new MagSafe to MagSafe 2 adaptor. That would work for most devices, but perhaps not all -- some speaker sets, for example, have a cradle that won't be physically capable of supporting the phone with it propped on a dongle that adds a half-inch or so of height. Devices like Nike+iPod will look a little ungainly sticking even further out of the device. Of course, these adaptors won't be free, and I'm sure Apple won't object to making a little extra scratch from them -- particularly if people choose to buy one adaptor for each of their legacy devices, to save the hassle of moving them around from device to device.

Households with lots of iOS devices of mixed generations will be inconvenienced too. Right now, I have three Dock cables next to my bed -- for my iPhone 4, my wife's iPhone 4, and my iPad. I have one in the office, a couple downstairs that float around between chargers in various rooms when we need it, one at my desk in work, a couple in my travel kit, and two in my car. We're used to being able to use any charger and any cable with any of our devices. A new port means I'll be back to having to think about where and when I might need a cable again, which is going to be a low-level annoyance until I finally snap and order half a dozen cables from eBay. Or, I'll have to buy a handful of adaptors, then keep attaching and detaching them as necessary -- and trying not to lose them when they are detached.

The bottom line

If I were a gambling man, I'd wager that we were getting a new, smaller Dock port on the new iPhone. I don't think it's certain, by any means, but I think it's more likely than not; the reasoning I've outlined in this post strongly suggest to me that Apple has the means, the motive, and the opportunity to put the old timey Dock port to sleep. The work Apple has put in to forcing through the nano-SIM standard shows just how ruthlessly focused it is on space-saving within the iPhone, and the fiddling it has done with micro-SIMs and the new MagSafe 2 port shows it isn't scared to inconvenience us users to achieve these goals.

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