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The State of Video Connections
mikemuch writes "Joel Durham provides a nice rundown on what's happening in video interfaces as we leave VGA behind and move through the DVI flavors, visit HDMI along the way, and look forward to UDI and DisplayPort."
Spare your eyeballs with the ad free, one page print version.
Most of my monitors are 19-inch CRT monsters. They do what I need them to do, they deliver a pretty image, but they're old. I still have a ViewSonic Optiquest V95 in service that dates back to around 1999. It's a VGA monitor, as are all of my displays. I shudder at the idea of updating them, not because of some sentimental attachment, but because connecting displays to computers has become so darned complicated.
The analog VGA was the standard for such a long time, some of us just got used to it. Today, I don't remember the last time I got a performance-grade graphics card with a VGA port on the back of it; I have a small cadre of DVI-to-VGA adapters that I use to plug in my monitors.
DVI as a standard features a number of sub-standards, some analog, some digital. Now DVI is already seeing the writing on the wall due to its limited bandwidth, just as the world grows accustomed to it. HDMI is crossing from the TV set to the computer, UDI is creeping into the market, and DisplayPort is riding over the horizon and hoping to take over the world.
What if you just want to play Supreme Commander or do your taxes? Can't you just poke a monitor cable plug into a display adapter and be done with it? Sure you can, if you know what to expect when you face the next generation of graphics-to-display connections.
VGA
Sure it's old, but it still works. Video Graphics Array (VGA) has been around since 1987, a few years after which it became the standard connection between the PC and its monitor and stayed that way for more than a decade. If you happen to purchase an analog CRT monitor, even one made today, it's likely to require a VGA connection to a computer.
The term VGA has come to mean a number of things. In one sense, it's used to refer to the actual port found on a graphics card or the corresponding plug (a 15-pin mini D-sub male) on a monitor cable. VGA is also sometimes used to describe the outdated and rarely used screen resolution of 640x480 pixels, which was once considered sharp and sexy.
VGA Connector
click on image for full view
VGA graphics cards date back to the days of ISA expansion ports. Such cards were typically capable of addressing only 256K of local memory and displaying 256 colors at 640x480 at a 70Hz refresh rate. As demand grew for higher resolutions and more robust graphics support, the original VGA spec became outmoded but the connection port was preserved.
VGA is analog. Graphics cards with VGA compatibility employ RAMDAC (random access memory digital to analog converter) chips to pipe digital graphics signals through the analog display cable. Of course, with digital displays like flat-panel monitors being all the rage, it would be even cooler to have a direct digital-to-digital connection from PC to display, wouldn't it? That's where DVI came to the rescue.
DVI
DVI stands for Digital Visual Interface. As digital flat-panel monitors started to become the rage at the tail end of the last century, the analog VGA connector quickly became inadequate for the needs of such displays. The DVI port is quite different from that of VGA: It's made up of up to 24 pins (most of which are for TMDS) and an additional five pins for analog compatibility. TMDS stands for Transition Minimized Differential Signaling; it's a high-speed serial interface used by the DVI and HDMI display standards.
DVI comes in three flavors:
* DVI-A, in which the A stands for analog. This type of DVI connection only transmits analog signals and is intended for use with CRT monitors. You almost never see DVI-A.
* DVI-D, the D meaning digital. This is purely digital, without any analog compatibility at all.
* DVI-I, with the I standing for integrated. This connection carries both analog and digital signals and can be used with either analog or digital displays. This is the most common DVI connector found on graphics cards.
To further complicate matters, DVI-D and D
What's with these never ending fscking changes? Obsolescence built in, incompatible formats, changing far too frequently. Bullshit DRM "features" in each new revision.
Please stop this crap! Just give us simple digital connectors and let the boxes talk to each other. How about something plain and simple 10Gb Ethernet?
This article pimps UDI, which uses an HDMI-backwards compatible plug and can do higher bandwidth (10.8Gbps) and HDCP (copy protection enforcement).
Unfortunately, HDCP implementation sucks. Standard procedure for the problems almost everyone has with HDCP-enabled cable boxes is to *reboot the box*. Apparently, in the exchange of encryption keys a handshake sometimes gets dropped, and nobody has a firmware solution.
Of course, even it worked right, HDCP would still suck.
VGA isn't going anywhere until we replace all our KVM rack switches and who needs HD for a TTY?
Perhaps this is because even a modest resolution (by today's standards) needs nearly 2Gbps of bandwidth?
Do the math your self: 1280 x 1024 x 24 x 60 = 1.887Gbps
This doesn't even begin to take into account any protocol overhead, sync signals, or other useful data such as audio.