DisplayPort now part of the MacBook lineup


In Part 1 - Cost, I wrote about the inevitably of DisplayPort becoming the dominant display interface standard for PCs and handheld devices, if for no other reasons than cost:
In Part 2 - Performance and Design, I reviewed some of the performance advantages of DisplayPort over DVI and to some degree, HDMI:

In this third installment I want to look at DisplayPort in terms of its potential for future digital devices relative to DVI and HDMI.
Unlike DVI or HDMI, both of which include legacy technology for CRTs, DisplayPort was designed specifically to handle today’s digital displays and to be able to adapt to new features in the displays and devices of the future.
The 45-nm Holy Grail of Chip Size
Chip makers from Intel to AMD to Nvidia are striving to reduce die size to 45-nm and smaller in order to reduce power consumption and increase transistor count. However, a 45-nm process imposes a technical limitation of 2.5V maximum for I/O transistors. HDMI and DVI both use TMDS, which requires 3.6V when running high-speed signals (up to 5.25V for low-speed sideband signals).
The only way around this limitation for HDMI and DVI is to add proprietary, custom circuitry. This translates into increased complexity and increased cost.
DisplayPort in contrast, requires less than 2V for high speed signals, so it can be integrated with a standard 45-nm process - no custom circuitry, no added size, and no additional costs.
Picture-in-Picture and Daisy Chained Displays
As already discussed in Part 2 - Performance and Design, DisplayPort was designed as all digital and uses micro packets to bundle audio, video, and data information. This micro-packet protocol is designed to support more than one audio or video stream, as well as data - all over a single cable. The current DP specification allows for up to six 1080i streams or three 1080p streams. So in the future you should expect to see things like Picture-in-Picture or daisy chained-monitors without additional cables or circuitry.
USB, Webcams, and Touch-Sensitive Displays
DisplayPort not only offers a scalable data channel, it offer a bi-directional scalable data channel. This means that future implementations will be able to support microphones, webcams, USB hubs, or touch-sensitivity built right into the display - without additional cabling and circuitry (this would be especially valuable on laptops where physical space is at a premium).
Dongles and Backwards Compatibility
DisplayPort may be the future, but since a lot of us are dealing with existing displays, laptops and consumer-electronics devices, there will be a need for adaptor cables or dongles to bridge between HDMI/ DVI and DisplayPort.
DisplayPort already offer pass-through support for HDMI signals. So using the appropriate dongle you can hook up your DVD player or cable box to a DisplayPort monitor. Coming later this year, expect to see adaptors that will allow you to connect your DisplayPort video card, to an HDMI or DVI device.
Final Score Card
So let me update my score card:
| Feature | DVI | HDMI | DisplayPort |
|---|---|---|---|
| Price | +1 | 0 | +2 |
| Sleeker Displays | 0 | 0 | +2 |
| Smaller Connectors | 0 | +2 | +2 |
| Resolution & pixel depth | +1 | +2 | +2 |
| Long cables | 0 | +2 | +2 |
| Auto-tuning | 0 | ? | +2 |
| Audio | 0 | +2 | +1 |
| Smaller Chips | 0 | 0 | +2 |
| Picture-in-Picture | 0 | +1 | +2 |
| Webcams & Touch Displays | 0 | 0 | +2 |
| Compatibility | +1 | +1 | +1 |
While there is not a clear winner between HDMI and DisplayPort for today's market, in the near future the demands for the, cost benefits, performance, and scalable spec of DisplayPort will become more commanding. The FirePro line from AMD, as well as 30-bit color monitors from Dell and HP, are strongly embracing DisplayPort (but still hedging with at least one legacy DVI port) and I expect to see more card and display vendors move in this same direction next year.
Addendum: For the complete 3-part series on DisplayPort see:
For a while, it was feeling like the Radeon HD 4870 had taken the lead in advanced hardware over the FireGL line (CAD-optimized drivers and RAM aside). But today AMD updated its flagship FirePro workstation accelerator to offer the same technology that has made news in the Radeon HD 4800 series: 800 unified shader processors and GDDR5 memory. But the FirePro v8700 also brings 1GB video memory and optimized drivers for CAD, digital video editing, and 3D visualization. It also adds twin Display Port connectors for the latest generation of hi-rez, hi-refresh, 30-bit color rendering displays as well as a dual-link DVI connector for older monitors. AMD’s press release claims a 40% performance gain over previous FireGLs.
In Part 1, I talked about the inevitably of Display Port becoming the dominant display interface standard for PCs and handheld devices, if for no other reasons than cost:
Cost aside, now I want to look at Display Port performance and features relative to the incumbents DVI and HDMI.
(Note: companies like Dell publicly contend that Display Port and HDMI will coexist to meet different product applications - but read in to what they say and you can't help but to compare!)
Ultra-thin displays

Smaller connector
Display Port and HDMI offer more than twice the performance of DVI in a much smaller package than DVI connectors. And they are more user-friendly to connect - without screws!
Over 1 billion colors
Single-link DVI has enough bandwidth to display resolutions up to 1920x1200 with 8 bit color (up to 16.7 million colors) at 60 Hz. Dual-link DVI doubles the bandwidth to support a maximum resolution of 2560x1600 with 8 bit color at 60Hz.
HDMI 1.3 and Display Port both support a maximum resolution of 2560x1600 at 60 Hz with 10-bit color - that over 1 billion colors, enough to eliminate color banding and offer sufficient gamut to edit video destined for a digital cinema theater (check out the new HP DreamColor).
Longer cables
Display Port supports full bandwidth (2560×1600) transmission for cables up to 3 meters, and 1080p transmission for 15 meter cables - significantly greater than DVI (5 meters) and about the same as high-quality (but higher cost) HDMI cables.
Automatic fine-tuning
Display Port features a unique scalable bi-directional auxiliary channel that source-destination handshaking such as the display requesting stronger signal quality if the signal has too much jitter or interference. So you can have a feedback mechanism between the display and the source for automatic fine-tuning. On top of this, Display Port embeds the clock signal as part of the link stream. This means fewer wires so less RFI and better transmission.
Digital, Audio and Data
Like HDMI, but unlike DVI, Display Port can handle both audio and video (as well as data) over single cable. Since most computer displays do not include speakers, the value of audio in the stream for HDMI and Display Port is questionable for computer devices. But of course, support for audio is valuable for consumer electronics devices like TVs and it might end up be very valuable for things like digital projectors.
But unlike DVI or HDMI, Display Port is all digital and uses micro packets to bundle audio, video, and data information. This means that Display Port can freely trade off pixel depth, resolution, frame rate, and the presence and amount of audio and data in the stream. Basically this means a lot of flexibility for different devices of any type (as well as the possibility of things like picture in a picture).
The Data stream in Display Port also has some significant implications I will discuss in the next article in the series (hint: data means support for USB links, cameras, microphones, and touch-sensitive displays).
So let me do my own little score card so far:
| Feature | DVI | HDMI | Display Port |
|---|---|---|---|
| Price | +1 | 0 | +2 |
| Sleeker Displays | 0 | 0 | +2 |
| Smaller Connectors | 0 | +2 | +2 |
| Resolution & pixel depth | +1 | +2 | +2 |
| Long cables | 0 | +2 | +2 |
| Auto-tuning | 0 | ? | +2 |
| Audio | 0 | +2 | +1 |
Basically DVI is antiquated and struggling to keep up with the ever increasing demands of bandwidth, resolution and flexibility.
There is no clear winner between HDMI and Display Port. Display Port is rapidly making its way into the PC market, while HDMI already has a strong hold on consumer electronics. For the foreseeable future they will co-exist (but I am sure they will compete), with DVI slowly fading out of the picture.
Addendum: For the complete 3-part series on Display Port see:
VGA, DVI, Dual-Link DVI, HDMI, and now Display Port. The display market is getting crowded with standards. I’m one of the many individuals in the computer industry who believe that the Display Port is the way of the future. Why?

Display Port was designed as an alternative to digital-display-interface incumbents HDMI (its consumer electronics competitor) and DVI (the current PC standard). It definitely improves some aspects of HDMI and DVI for certain applications. However is this enough to cause a new standard to overtake a more established interface? I think so and I think the reason can be broken down into three primary factors that I will cover in three separate posts:
Display Port lowers display-to-interface costs in several different ways:
First, Display Port avoids the annual $10,000 license fee (this was reduced from the whopping $15,000 original license fee) associated with HDMI. The HDMI license fees are on top of a per device cost royalty (estimated at four cents per device). Display Port is an open standard so there is no license fee. There are per device costs since Display Port also shares the dubious honor of supporting proprietary DRM (digital rights management). So even if HDMI and Display Port were technically equivalent to the consumer, $10,000/per year will be a significant motivator to computer parts manufacturers.
Second, Display Port consolidates both external and internal display connections with direct-drive technology (similar to the technology used in the original VGA). With Display Port monitors, there is no need for scaling circuitry within the monitor or front-end electronics. The monitor can handle frame-rate and analog-to-digital conversion. This streamlines the implementation of many tasks that are currently supported by multiple components within a computer display (saving $5 to $10 per display).
The cynic in me wonders whether these shifts in cost will actually be passed on to consumers. But regardless, they are definitely a driving factor why so many influential computer parts makers - Intel, Dell, HP, Phillips Samsung and graphics card makers AMD, Nvidia, to name just a few - back the interface and are adding it to new products. For them, Display Port is simply the smarter economic choice so there will be no going back.
While cost may be the prime motivator for computer parts manufacturers, Performance and Design is what will be of most interest to the rest of us. I'll tackle that in my next Display Port post.
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