Older than dirt
Originally published 2006 in Atomic: Maximum Power Computing Last modified 03-Dec-2011.
I'm not certain, but I think I've found the oldest electrical component in a normal PC. Just in time for everyone to stop using it.
When the "VGA connector" first emerged from the primordial swamp, the most it had to do was move 307,200 pixels (640 by 480) at a maximum refresh rate of 70Hz.
Those pixels could also only be in one of sixteen colours, but that doesn't matter. You see, VGA was the first PC video standard to transfer the image as an analogue signal, using one wire pair per colour signal for red, green and blue. And in analogue video it's the frequency, or "pixel clock", that determines the bandwidth of the signal. Colour depth just affects the smoothness of the colour signal waves, not how many of them there are per second.
When VGA came out in 1987, though, though, the connector it used was already familiar.
The original VGA connector was a nine-pin "D-subminiature", just like the standard small RS-232 serial connector that some rugged traditionalists still use today.
The earlier PC graphics standards used the nine-pin D-sub, too. CGA, EGA, the text-only MDA; all D-sub. Even IBM's three-board pre-VGA "Professional Graphics Controller" (1984 price in today's money: $US8000) used it.
And what do you know - that old connector worked for 640 by 480, too!
What we colloquially call "VGA" today is, of course, just a tad more demanding. Here in 2006, I've got a 21-inch CRT on my desktop; it's running at 1600 by 1200, 85Hz. That's about 7.6 times the maximum bandwidth of original VGA.
And yet it works.
Ah, I hear you say, but the connector isn't the same any more.
You're right, of course. Nobody uses DB9 (which should actually, technically, be called "DE9") for video any more. The "VGA" connector has, for years now, been the high-density 15-pin D-sub - which you should call "DE15", except nobody will know what you mean if you do.
The extra wires from the 15-pin plug only carry stuff like monitor ID data, though. There are no real new signal pins; 15-pin VGA isn't even like 80-wire ATA cables with their interleaved earths to reduce crosstalk. Provided the wire and plugs are good enough quality, you can adapt 15-pin VGA back down to 9-pin VGA for transmission and lose nothing but the computer's knowledge of the monitor's specs.
As far as the actual video transmission goes, not a thing has changed since VGA was young. And very little has changed since the first MDA adapters.
Well, big deal, you say. There are other PC connectors that've survived pretty much unchanged for a couple of decades.
Indeed there are, Grasshopper, but do you know how old the D connector actually is?
Go on, guess when it was invented.
1980?
1971?
1965, maybe?
Nope.
Nineteen fifty-two.
The D connector was born in the same year as Christopher Reeve, Dee Dee Ramone, Douglas Adams and Liam Neeson.
Will Riker and Worf were both born in '52, as well. (Well, the actors were.)
Billy Hughes died in 1952.
He was born in 1862.
In 1952, there was exactly one computer in Australia.
What I'm saying is, D connectors are OLD.
(Younger than Huey Lewis, though.)
(And BNC connectors, by the way, are a few years older again. BNC was designed to carry microwave frequencies, though, so video is no big deal for it. And BNC-connected monitors have always been rare in the PC world, so BNC doesn't count as a standard PC connector.)
It's barely possible that edge connectors, as used for expansion cards and memory modules, are older than D connectors. Printed circuit boards were used in quantity in the last few years of World War II, and edge connectors are a natural way to mate PCBs together.
But the modern expansion card's edge connector is two-sided and high-density; it's similar only in basic layout to the oldest ones I've seen.
You can, in contrast, plug a 1952 D-plug right into a 2006 D-socket.
Cannon Corporation, who're still a big name in the world of plugs and sockets, did not expect or intend their "D subminiature" connectors (which really were "subminiature" by the standards of a world where transistors existed but transistor radios didn't yet) to be used for high-bandwidth communications. Heck, they barely even expected the things to have to carry alternating current.
And yet here one is, more than fifty years later, happily squirting 163.2 million pixels per second, plus vertical blanking interval, onto my monitor.
D-sub is finally yesterday's news, of course. We've now got the Digital Visual Interface (DVI) connector. The "DVI-I" version is the one commonly seen on video cards; it's got a cross-shaped arrangement of contacts to the side of the digital pins. Those are the analogue RGB contacts, and they're much better suited to moving high-bandwidth video than is the antediluvian D connector.
But if you've got a monitor that you want to connect to those well-designed high-bandwidth RGB pins, you have to use... a DVI-to-VGA adapter, because there are very close to no analogue monitors with DVI plugs.
(I thought there were none at all, until a reader pointed out this IBM screen to me.)
If you're adapting DVI to VGA, then... welcome back to '52.
(Here in Australia, we won't even have television for another four years. But there's a bit of lovely trench warfare going on in Korea; you might like to check that out while you wait.)
So, if you're still using a monitor with a "VGA plug", feel free to raise a glass to a very old trouper as it trundles off into the sunset.
And count yourself lucky that the same thing didn't happen with valves.
