Why Thunderbolt Won't Come to the iPhone Anytime Soon
by Anand Lal Shimpi & Manveer Wasson on January 14, 2012 6:55 PM EST- Posted in
- Smartphones
- Apple
- Intel
- Thunderbolt
- Mobile
- iPhone
- SoCs
Before CES there was a bunch of silliness floating around about how Apple might bring Thunderbolt to the iPhone based on a creative interpretation of an Apple patent. Some folks even theorized that Thunderbolt would bring about faster sync. I meant to address the speculation before CES but I never got the chance to. Now that I'm done with most of what I needed to cover from the show, I can get to what I planned on earlier.
Lightpeak, the basis of Thunderbolt, was an Intel designed spec. When it came time to productize it, Apple and Intel collaborated to turn it into Thunderbolt. According to Intel, the bulk of their technology collaboration with Apple focused on the cable and connector design. The spec itself and the Thunderbolt trademark both remain property of Intel. Apple did some of the initial trademark filing for Thunderbolt, but eventually transfered ownership to Intel.
Intel is the sole owner of the Thunderbolt spec. Building Thunderbolt devices requires a license to use the spec but no royalties need to be paid to Intel. Intel is also the only supplier of Thunderbolt controllers. Without Intel's permission, no other company can make a Thunderbolt controller.
This last point is extremely important. The chances of Intel building a Thunderbolt controller for an ARM platform are very slim. Intel could eventually allow Apple and other companies to make their own Thunderbolt controllers, but that decision is Intel's alone to make.
Furthermore, Thunderbolt requires both DisplayPort and PCIe (x4) interfaces to work. To the best of my knowledge, no modern ARM based SoC (Apple's A5 included) features DP and sufficient PCIe lanes. Apple could admittedly add support in a future SoC, but again, Intel would have to build a controller designed for low power operation in a smartphone or tablet. The cost of the controller would also have to be reduced significantly. Current Thunderbolt controllers cost between $20 - $30, that's just as much if not more than Apple spends on building the A5. Thunderbolt controllers will eventually get down to the single digit dollar values, but not anytime soon.
Thunderbolt supports some extremely high speed signaling, which complicates board design, also contributing to higher costs. The cables are also fairly pricey, which Apple would presumably have to include in the box if TB were to truly supplant USB as the iDevice sync cable of choice. Finally, for today's usage models, Thunderbolt makes no sense to deploy on a smartphone or tablet. The NAND used in high-end mobile devices is 2-bit MLC in a single package of 1 - 8 die depending on storage capacity. The NAND is typically paired with a controller either on-package or integrated into the applications processor (this is how the iPhone works). That controller is good for performance in the tens of megabytes per second, not anywhere close to the 1GB/s that Thunderbolt can offer. Headroom is the enemy of good low power design. Implementing an interface that can transfer at 1GB/s when you're only going to use 5% of that is not good engineering.
Thunderbolt was built to further enable the notebook as a desktop usage model, and to enable notebooks to continue to shrink in size by allowing extra controllers and functionality to be delivered through external devices without compromising performance. Smartphones were never the target for Thunderbolt to begin with.
It's clear that WiFi will be used for both sync and driving external displays at some point in the not too distant future. With 802.11ac we'll likely be able to exceed the performance of NAND, even as ONFI 3.x based NAND arrives later this year and in 2013. Apple has already implemented AirPlay on the iPad and iPhone 4S, enabling some form of wireless display support. As WiFi Direct and WiFi Display become more prevalent however, this will likely be the path to connect smartphones/tablets to external displays.
All modern mobile SoCs include a hardware video encode block that is very low power. It's far more efficient to simply dump the frame buffer into a video, encode it in real-time to H.264 and transmit the low bandwidth signal over WiFi Direct to a display for decode/display. Using Thunderbolt in this case just wouldn't make sense. Mobile devices are all about portability and removing wires, not adding faster, more power hungry ones.
That's what I believe will happen. Apple may eventually move to USB 3.0, but sync and external displays will be done over wireless technologies. Thunderbolt remains a very high performance spec that we'll see limited to notebooks and desktops for the foreseeable future.
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stubeck - Saturday, January 14, 2012 - link
It scares me that people think this would be added, or that there would be any benefits to it. It must be the same people who think any flash is super super fast no matter what its cost.B3an - Sunday, January 15, 2012 - link
Look at the site it's from though lol, including graphics and the writing at the top there. The whole thing has a very religious-like iCult feel to it. It's actually bizarre and quite disturbing. The site seems to be made by some truly messed up iCult users that likely have real mental issues.secretmanofagent - Saturday, January 14, 2012 - link
I'm curious why the sheer size of the port isn't mentioned. Does Thunderbolt require the connectors to be a particular type in order to meet the specifications, or could you connect TB to a 30 pin connector? If the former, I don't see why Apple would ever use it.DanNeely - Saturday, January 14, 2012 - link
If they actually were going to do it; they'd come up with some sort of micro connector; or maybe abuse the existing dock connector so it can tell if it has a dock or TB cable and output the proper signaling to the cable.All a moot point since TB is years from being relevant in mobile (if ever).
solipsism - Saturday, January 14, 2012 - link
There are FW pins currently unused in the 30-pin connector.DanNeely - Sunday, January 15, 2012 - link
Probably not enough to just re-purpose though (and you'd still need to make the hardware able to tell if it was connected to an FW cable or a TB cable). A pinout for the dock cable shows 8 pins for FW (4 for data, and 4 for power). Thunderbolt has 20 pins, 13 of which are apparently used for data/control signals.repoman27 - Tuesday, January 17, 2012 - link
I'm pretty sure they've already repurposed the FW pins for digital video output (HDMI via the Apple Digital AV Adapter) on newer devices. And, as DanNeely points out, you'd need at least 8 pins for TB data (2 sets of send/receive pairs) and although there are 8 pins for FW in the 30-pin connector, the power pins are usually ganged together.solipsism - Saturday, January 14, 2012 - link
Surely you don't need an Intel processor in both ends for this to work or all the TB compatible devices shown at CES would be unusable. Doesn't the $50 TB cable allow for maximum transfer, something that simply won't be possible on such a device, so a much cheaper cable could be used to negotiate a much slower — yet faster than USB2.0 — speed?Anand makes a lot of great points as to why this won't happen but I wouldn't think that USB and TB would be mutually exclusive, just like FW and USB weren't. It would also be a way to get TB better traction and we already know that Apple and Intel have a year long deal with the launch of TB.
Also, is that 30-pin connector still holding strong or is it getting long in the tooth after almost decade of service? It doesn't fit flush with the iPad 2 port but I can't imagine a thinner port being more durable than what they currently use.
Penti - Sunday, January 15, 2012 - link
They just host a PCI-e adaptor, a ordinary storage controller same one you would put on a PCI-e add in board. It's just a PCI-e SATA controller. The cable is just "special" because it transfers two very different signals over it's own protocol and there is already third party cables ready to come out that would probably be a bit cheaper. It's not meant to replace Intel's yes Intel's USB 3.0. It's just that Intel didn't implement it until Ivy Bridge and thus not Apple either. Other SoC-providers have started or will have USB 3 support.A adaptor cable converting PCI-e to a more communicative and useful protocol like USB 2/3 would be pointless to implement. Also it wouldn't be much point trying to use TB in host mode to use those external devices, it's much easier to do with USB that has mass-storage or MTP or whatever standard. No need for native device drivers for the PCI-e device which also means you don't need any drivers or converts with common drivers to communicate with the iPhone/iPad. Connecting a Thunderbolt cable to a device which not fully supports it is also pointless as it would mean you can not daisy-chain to a further device.
Other devices will just use Micro-USB and MHL. Ordinary micro USB for transfers and MHL-cable for video output. A MHL-adapter is like 25 dollars. Docking seems a bit pointless now days when we just don't have Bluetooth A2DP but also wireless DLNA-streaming and what not. Also NFC and BLE/BT4.0 or whatever.
An ARM-device could host a PCI-e to USB chipset and use thunderbolt to be a device which can accept a Thunderbolt connection to that USB-controller and input a DP signal to the device if they use Intel's controller chips. The other way around is also possible but you wouldn't be able to connect that to your computer. PCI-e to PCI-e doesn't work. Connecting a Thunderbolt HDD to that ARM-device wouldn't work if it aren't possible to run the ARM-device as a host driving the TB, otherwise it would just show up as a TB device on your computer connected into that chain. The Thunderbolt-controller wouldn't fit in a phone though. Certainly not useful in those scenarios even if a slave device can use the TB-chips and hardware as an end device where your computer is the host and is driving it. USB can already act as both Slave and Host in these devices solving those issues.
You could rather see Thunderbolt as way not to have to deal with technologies like ExpressCard, or as a docking cable that can be daisy chained so you can connect to your notebook and get DP, Ethernet, USB, FW, External harddrives, professional hardware and other devices connected via one connection, which of course is very different from how USB 3.0 is used. Doesn't make either useless or redundant. If you like to connect a camera or a drive, or a phone you would probably do that over USB. Having that on board means you don't need to go through your converter, dock or whatever.
twotwotwo - Sunday, January 15, 2012 - link
"Headroom is the enemy of good low power design" -- well put.