Docking 201 – Second in a Two Part Series

Today we'll look at what I promised last time – a more advanced look at docking and some of the things that ThinkPad engineers have to trade off as they are designing next generation docking solutions. Docking is one of those subjects that makes me cringe whenever a customer brings it up in conversation. It means one of several things, none of them particularly enjoyable to talk about: End of life for current docks, lack of a needed port, compatibility issues, or functionality problems. All people who use docking seem to have a strong opinions on the subject. While there are some similarities, there is very little consensus as to what the "ideal" solution is. Just a reminder, for purposes of this post, I am using "docking" as a generic term to mean anything that allows cable management on a notebook PC. When the differences are important, I will break out and delineate them.

USB DOCKING When we design a docking solution for a product, it is not just as easy as putting a connector on it and that's it. The easiest way out is to use a USB port already on the system. As vendors we do not need to do anything special to the notebook. A user simply plugs in their USB port replicator and it works. The disadvantage is that while USB is ubiquitous, it has major bandwidth limitations, allowing only 480 Mb/s data transfer rates. This is just nowhere near enough to have high quality digital video + Gigabit Ethernet + other USB devices. While USB 3.0 would seem to be a solution and is on the horizon for next year (if the industry gets its act together and stops bickering), it still will not be fast enough. While the standard will up the speed to 4.8 Gb/sec, this is barely adequate for full high definition video and will not be enough for video plus all of the other devices you may want to connect. However, it will bring about a radical improvement and may end up being adequate for many.

DEDICATED DOCKING To get around the bandwidth problems, vendors add their own proprietary connectors underneath or on the sides of their systems. Putting a connector on the side of a system is most convenient for the user, but doing so takes up valuable real estate that could be used by additional ports. Putting the connector on the bottom solves the space utilization problem, but it does require special design consideration so that the user does not have to "hunt" to try and find the proper alignment to snap the notebook in place on the dock. An additional disadvantage to bottom docking connectors is that they add thickness and therefore weight to the system. If you look at a docking connector closely, you'll see two to four rows of closely spaced wires (or "pin outs" as they're commonly known in the industry). Each of these pins has a dedicated function and connects directly into the notebook's expansion bus for maximum speed and compatibility. Some minor functions like PS/2, serial, or floppy disk drive functionality only require one pin or so. Other more advanced bandwidth-hungry functions such as video or Ethernet require 2 or more wires to successfully transmit data back and forth. There are also wires dedicated to providing power and grounding. As we add more functions, ThinkPad engineers have to start making tradeoffs as there simply aren't enough wires to do everything we want. Want more than 2 USB ports externally? There go 4 additional wires? DVI? Twelve. And so on… We could theoretically add more wires and get around this, but as the docking connector size increases there are not only electrical issues to solve, but the connector gets to be so physically big that it takes up valuable real estate on the notebook itself. This is why our X Series Ultraportable ThinkPads do not share a common dock with our T, R, and Z series notebooks. The docking connector is physically smaller which makes it incompatible with the docks its bigger cousins use. Our Product Marketing team determined that adding the same size connector as the T and R series would have grown X Series thickness and weight to unacceptable levels for an ultraportable (where size and weight are THE considerations). In fairness, not everyone shares this same view. There are customers who would much rather have common docking with the rest of the product line and would be happy to have thicker and heavier ultraportables to achieve this. In fact, one of our customers, a large retailer in the UK, actually buys our old ThinkPad X31 notebooks on the tertiary (!!!) market just so that they can have common docking with their current port replicators and docks that they have installed in their hot desk environment.

COMMON DOCKING Another common question I commonly get goes something like this: Docking is SO expensive for me as a customer and I don't like to manage the complexity of having multiple expansion devices in my user environment. Why can't you just keep the same ones you have always had for 5, 10, or even 50 years? Though many people accuse us of the contrary, we don't want to change docking solutions. We don't want to drive customer dissatisfaction. Many customers upon hearing that they will have to update their expansion options use it as an opportunity to go out to RFP. The line of thinking goes something along the lines of "Well, if I have to spend money to update my fleet of expansion docks anyway and start fresh, I might as well use the opportunity to see what other vendors have to offer." Customers are won and lost over docking changes. We change docking primarily to add functionality and secondarily to add usability improvements. If you still had your docks from five years ago, you'd still be connecting with USB 1.1. You'd also only have one or two USB ports. There would be no digital audio out, your video resolution out would be extremely limited, and so forth. From time to time, as the industry changes, vendors must change docking simply to keep up with the times. On the horizon are other "must have" ports like DisplayPort or USB 3.0. Each of these will require architectural changes (i.e. more pins) in order to accommodate them. While vendors strive for compatibility with older systems, sometimes adding support for the latest and greatest means changing the number of pins and/or changing what each pin does. You don't want your ThinkPad trying to get a video signal from the power input, for example.

RIP AND GO Another question: "Why do I have to push the eject button on my port replicator or dock. Why can't I just rip it off the port replicator and go?" Everyone, especially our usability team, would love this to be so. Unfortunately this is out of our control. Architecturally, the way Windows is written, taking a device off without notifying the operating system can cause "bad things" to happen. Bad things can be anything from system hangs to data loss, to blue screens of death. You are much more likely to have a problem if you have a "legacy" serial or parallel device connected to your port replicator or dock. If you just use USB devices, you'll probably get away with it, but play in the deep end of the pool at your own risk.

WIRELESS AND THE FUTURE OF DOCKING I've saved the most interesting part for last. Long term, physical docking becomes irrelevant. Just about every problem we have with docking today can be solved with a wireless docking solution. The one exception is power. There is no way that wireless power is going to be ready for mainstream use anytime in the next few years. Wireless docking in theory sounds like a panacea. Just plug all of those wires into a centralized wireless hub, and then use radio waves to bounce the signals back and forth from the wireless hub to the notebook PC. You can literally sit down at your desk and be connected to your peripherals instantly. Alas, what will be perfect in the future ain't ready today. (Bad grammar for emphasis). Again, we get back to the problem of bandwidth. There just isn't enough. The most promising technology is Ultra-wideband (UWB) which is a very efficient way of transmitting high amounts of data over short distances using a wide portion of the radio spectrum. It is pretty much interference free and a currently shipping standard. You may know the technology by its commonly used name, Wireless USB, which is a software protocol imposed on the physical UWB medium. If that last statement left you totally confused, don't worry. It's not that important. UWB technology is very good and very fast, but it still isn't fast enough for PC needs. One problem is that its range falls by the square of the distance between the hub and the radio. A reader asked about a competing vendor who has been shipping wireless port replicators and why their range was so limited. This signal fall off problem is why that is so. With time the engineers will find a way to add more wireless bandwidth to systems. For now, it is possible to use things like compression to increase the effective bandwidth. This is often done with video in which an interface out of the graphics processor intercepts the raw data, compresses it, and then sends it to the wireless hub. Once it arrives, the process is repeated in reverse and the image shows up on your display screen. The subsystem is intelligent enough to send only the changes in the image and thus save bandwidth. When you are using something like an email program, this is not an issue. However, crank up your copy of the Matrix and start watching the lobby gunfight scene, and you've got some problems. And this is only for one display. Adding support for a second display means that you need to at least double the bandwidth. I hope this post provided some more insight into the world of docking. Feel free to expound or ask questions in the comments. As I mentioned in the last post, we are actively soliciting feedback and opinions on future docking possibilities. If you would be willing to provide some feedback by participating in this survey, our team would be very interested what you have to say. We will not use your information for marketing purposes (i.e. sell you out). Here's the link. If there's interest, I'll share some of those findings from the survey with you all at a future date.