Apple and the Mini DisplayPort
October 21st, 2008
Daniel Eran Dilger
A variety of people have offered their viewpoints on Apple’s use of Mini DisplayPort on the new MacBooks and LED Cinema Display. Assertions range from the insistence that Mini DisplayPort is “proprietary” to the announcement that it is actually part of the DisplayPort specification. As is often the case, nearly everyone is wrong to some extent.
DisplayPort vs Intel’s UDI.
Back in late 2005, Apple joined Intel, NVIDIA, and other manufacturers working to develop a new generation of technology to replace DVI graphics with a standard proposed by Intel called Unified Display Interface. The new port was intended to replace DVI with a cheaper plug interface and supporting circuitry. UDI fell apart early last year as industry momentum moved to support VESA’s DisplayPort instead.
DisplayPort fundamentally rethinks the DVI interface built upon VGA signaling, presenting a far better and more modern alternative to the “same but smaller and faster” premise of UDI, while matching the smaller port and cheaper implementation. DisplayPort also provides a variety of other features, including the ability to support internal video cabling (not addressed by DVI) and support for multiple displays over the same cable.
Over the last year, Apple worked with NVIDIA to deliver the 9400M integrated controller ‘chipset on a chip’ that could support DisplayPort graphics output. Starting with the new MacBooks, Apple shifted from Intel’s chipset integrated graphics to NVIDIA’s new integrated graphics controller, which will be used on forthcoming Mac designs to support the new DisplayPort graphics system.
Apple’s membership on the UDI working group calls to mind Apple’s early support for the Blu-ray consortium of the same period. Just because the company researches a technology or helps provide input and contributions does not mean that it will adopt or promote the technology when better or more practical alternatives become available.
DisplayPort Debuts on Apple, via Photoshop.
Somewhat ironically, the DisplayPort standard’s website depicts their port photoshopped onto a Mac laptop, which actually appears to be a PowerBook as it also has an S-video port.
In other pictures used on the site, the same laptop model is presented with the DVI port it shipped with. The site also portrays aluminum Cinema Displays as examples of ‘slim and modern’ displays using DisplayPort, although none of Apple’s aluminum Cinema Displays support the new port yet; the new LED Cinema Display that does offer a Mini DisplayPort looks significantly different than those pictured.
Further improving upon the DisplayPort specification right off the bat, Apple originated Mini DisplayPort to replace the rather large connector the DisplayPort specification describes. Both ports deliver the same 20 pins, but Apple’s Mini version is half the size and looks unique rather than being confusingly similar in shape and size to the neighboring USB ports as a full size DisplayPort would be.
Apple Plays Four Holes of Mini Port.
For the record, Apple has also originated mini-VGA, mini-DVI, and micro-DVI ports for use on its smaller form factor laptops.
Mini-VGA was used on iBooks, the 12“ PowerBook, and some models of eMacs and iMacs. The port was also used by Sony on some of its laptops. On Apple’s systems, the small Mini-VGA port provided the same VGA signals on a smaller jack, but could also enter a TV mode where it would supply composite and S-Video signals instead on the same pins. Exporting either set of signals required a dongle. The top resolution those machines supported was 1024×768.
Mini-DVI replaced the Mini-VGA port on late modeled 12” PowerBooks and all of the Intel-based iMacs, MacBooks, iMacs and Xserves starting in 2006. In addition to delivering VGA and TV signals, it can also carry DVI, although it only has the pins to support single-link DVI and therefore is limited to a top resolution of 1920×1200, which is what the new 24“ LED Cinema Display uses.
Micro-DVI was used on the first model of the MacBook Air in early 2008. This port was smaller and thinner than Mini-DVI, allowing it to fit into the Air’s tiny port panel. It also supports VGA and TV signals. Top resolution is limited to 1280×800, due to the Air’s limited Intel GMA X3100 integrated graphics processor.
Mini DisplayPort replaces the mini-DVI port on the MacBook, Micro-DVI on the MacBook Air, and the full size DVI on the MacBook Pro. Steve Jobs also announced that the new plug will replace the existing connectors on all new Macs going forward. The new port is small enough to fit on the Air but also delivers the high 2560×1600 resolution of Apple’s 30” Cinema Display, which requires the use of a Dual-Link DVI signal.
Is Mini DisplayPort Proprietary to Apple?
Proprietary is one of those words that pundits don’t seem to understand very well, so they use it whenever they want to inject a negative spin on a subject. Proprietary means “owned,” not “uncommon” or, as some seem to think, “not from Microsoft.” The opposite of proprietary technology is freely available, or at least easily licensed open standards.
The ISO standards body owns MPEG 4 H.264, but anyone can license and use it, so it isn’t regarded as proprietary. Apple released the FireWire specification to the IEEE standards body, which allowed anyone to use it or contribute towards it. Sony decided to ship FireWire on its cameras and computers without the extra pins supplying power and using a smaller connector; Sony referred to it as iLink. It was still protocol-compatible with the FireWire specification however.
Apple has a history of developing new hardware technologies where no viable alternatives existed, but also of using and promoting industry standards when suitable specifications are available. When it began shipping digital displays, Apple designed a port called ADC which put standard DVI, USB and power all in the same connector, so users had one cable rather than three. The connector itself was proprietary to Apple, but the signaling was industry standard, so extracting the signals only required a simple physical adapter.
Similarly, the iPod’s Dock Connector is a specialized port that put USB, FireWire, audio input and output, video, and digital remote controls all in the same package to fill a void that didn’t exist for anyone else. Anyone can build a compatible port, even if commercial developers may need to pay licensing fees to brand it as “Made for iPod.”
Who Else Will Adopt Mini DisplayPort?
DisplayPort is a VESA signaling standard anyone can use royalty free. It specifies a full size 20 pin connector that looks something like USB or HDMI (port and jack pictured above). Apple’s connector puts the same 20 pins in a much smaller port, meaning the connector is unique but the signaling is standard, as is the case with ADC, the Dock Connector, or even USB and mini-USB (of which there are at least two physically incompatible varieties!). That makes calling Apple’s Mini DisplayPort “proprietary” a bit of a stretch, but it’s also inaccurate to say that Apple took the connector from the spec, when it really didn’t.
Since there is no existing Mini DisplayPort in the VESA specification, Apple is contributing something new to the emerging technology portfolio that hasn’t yet been widely adopted. Mini DisplayPort may likely be used by other PC makers because it cleanly moves video standards forward while adding significant value in size reduction.
If other PC makers follow Apple’s lead, they’ll be able to deliver better graphics on their laptops using the superior signaling protocol used by DisplayPort and the more compact port Apple itself has standardized upon. If they instead choose to use the larger, full sized DisplayPort, Mac users will only need a physical converter cable, just as many Mac users today use DVI to VGA adapters or cables.
Apple’s lead is more likely to be followed now that the company is selling such a significant portion of consumer retail laptops, with roughly a fifth of unit sales and a third of the dollars spent on laptops. Those who don’t follow Apple’s lead will simply look behind the curve.
Thinking Outside the Display Port.
As with ADC or iLink/Firewire, there’s no electronic conversion needed between the mini and full sized DisplayPort connectors, although there is an electronic conversion needed to export a high resolution Dual-Link DVI signal from Apple’s Mini DisplayPort (or any DisplayPort), which Apple handles through a $99 converter. Extracting VGA or Single-Link DVI only requires a physical pin rearrangement for output, and therefore only demands a $30 dongle.
There’s currently no HDMI output dongle, but HDMI itself is just a repackaged DVI output, so HDTV users can plug in their Mac using the Single-Link DVI dongle and a standard DVI to HDMI cable. Apple does not route audio over the Mini DisplayPort, so there’s no way to push audio and video over the same connector as can be done with the HDMI-equipped Apple TV.
Support for composite or S-Video TV out is no longer an option. If you need to output really low quality, low resolution video from your Mac to a VCR or an old TV that doesn’t support digital inputs, you’ll have to settle for last year’s MacBook model. Like the removal of FireWire from the new MacBook, the loss of TV output is a bit aggressive and there’s no doubt that some might have a lingering need to export low resolution TV video from their laptop.
PC Makers Cling to the Past.
In contrast with Apple’s push to deliver the highest quality video output possible on its Mac laptops, the majority of PC laptops have only ever used full sized VGA connectors, and often supplied TV output (if they did at all) using a strangely unique connector, as IBM’s ThinkPads and Sony’s Vaios often did. Adding a DVI connector to PC laptops isn’t common because fewer PC makers consider their laptops to be worthy of being attached to high quality digital displays. Most corporate laptops only ever need to connect to VGA projectors or perhaps an old TV output.
On the other hand, a few PC makers have started putting DisplayPort on their displays. To put this in context, consider that Dell and other PC makers started putting USB on their PCs around the late 90s, but continued shipping PS/2 keyboards up into 2006. Similarly, Dell also has historically shipped its displays with both VGA and DVI connectors and cables, and attached the VGA cable by default as the recommended one, despite having used DVI-equipped video cards on its new PCs for several years now.
Serial, Parallel, ADB, USB.
PC makers have always had a strange dependance upon old legacy technologies. Not Apple; the company has always picked the best interface for the day, usually on technical merits but sometimes also to save costs. While early PCs used RS-232 serial (for cheaper and relatively low speed devices like modems) and Centronics Parallel ports (for faster devices such as printers and Zip drives), the original Mac adopted the faster RS-422 serial port for both modems and printers and networking as well, something no PCs in the 80s even gave any thought to providing.
Starting in 1986 with the Apple IIGS, the company began using ADB (Apple Desktop Bus), a universal serial port that could handle a wide range of daisy-chained input devices, from keyboards to trackballs to graphics tablets, in addition to the two RS-422 serial ports Macs used for printers, modems, and AppleTalk networking. A decade later, Intel introduced the same concept to PC makers under the USB specification, which intended to replace serial, parallel, and the simplistic PS/2 ports for keyboards and mice. Incidentally, IBM contributed PS/2 to the PC world at the same time Apple was rolling out its more sophisticated ADB.
While PC makers began putting USB ports on their PCs, there were lots of problems with hardware support and Microsoft didn’t immediately deliver full support for USB because nobody was using it, creating a vicious catch-22 situation that no leaders were able or willing to solve.
Apple rapidly transitioned to USB and removed ADB and legacy serial ports entirely starting with the 1998 iMac. It also shipped a terrible puck mouse with the iMac and its later USB-equipped desktops that helped spawn a huge USB mouse replacement industry and quickly made USB a popular standard. Earlier in this decade, Apple even dropped audio inputs from the Mac with the expectation that the market would simply use USB for digital audio input. It later added analog mic audio input back, along with digital optical inputs and outputs.
ATA, FireWire, USB.
The same history of Apple pushing the state of the art can be related in regard to drive interfaces. Apple pushed SCSI in the mid 80s back when PCs were using weird and simplistic hard drive interfaces. SCSI on the Mac not only supported higher quality hard drives, but could chain together multiple drives, supported CD-ROM well before it became standard on PCs, and also connected Macs to SCSI laser printers, scanners, and other peripherals.
Once PC economies of scale brought the price of ATA drives down and brought their performance up in the mid 90s, Apple began using the ATA standard for its optical drives and later hard drives to shave costs from the Mac. ATA devices can only support two drives per bus, a master and a slave drive, and aren’t designed to support peripherals. That’s why Apple had already started work developing FireWire as a replacement to SCSI for both disks and peripherals.
By the late 90s, FireWire offered unique speed advantages and media features. It also enabled the use of Target Mode, which Apple had pioneered on the PowerBook line as a way to access the laptop’s drive as if it were a hard drive enclosure, originally using SCSI and later using FireWire.
Intel released an updated specification for USB that pushed the standard from lower speed serial peripherals up into the realm of FireWire. Once again, the cost savings of economies of scale helped push USB 2.0 over FireWire in most consumer applications, including Apple’s iPod line. The new 13“ MacBook has dropped FireWire support entirely in response to consumer apathy for the interface in order to shave costs.
Meanwhile, Apple adopted the modernized, high speed Serial ATA interface for internal hard drives and optical discs, which also helped prevent FireWire from serving as a full replacement to SCSI on the faster end of the scale. MacBook Pros and Mac Pro desktops have supplied the faster FireWire-800 standard for some time, although the PC industry hasn’t supported its use and prices are still high relative to USB 2.0 or eSATA (an external version of the SATA interface). Apple also supports the very fast Fibre Channel interface on Xserves for SAN applications.
Ahead of the PC Pack.
Apple’s use of pioneering technologies has often meshed with its ability to open up new markets, from desktop publishing (which relied upon high speed serial networking and then SCSI to drive laser printers and scanners) to digital audio and video and the iPod (all of which benefitted from FireWire and USB). Pundits often revile Apple’s promotion of better technologies and bemoan its aggressive elimination of old legacy while celebrating or at least making excuses for the cheap, substandard alternatives often favored by commodity PC makers.
The company’s success in promoting better technologies at competitive prices, witnessed by Apple’s rapidly growing share of the markets it competes in, suggests that Apple’s aggressive stance in pushing new technologies and discarding outdated ones is the right path for a premium hardware maker serving progressive-minded, envelope tearing tech users. Dell and HP are largely stuck providing the low quality commodity parts their more conservative corporate customers want.
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