"When I first saw him, he was upside-down, and I didn't recognize his face," the Florida-based cell biology researcher said.
Davidson suspected at first that the tiny design he saw was circular patterns added to the chip to thwart attempts by reverse-engineers to deduce its inner workings. But a second inspection showed it to be the characteristically hard-to-find character from the children's book series. "I realized, 'This is a doodle of some kind.' Then I started looking over the whole chip. I discovered Daffy Duck and other things on that chip," Davidson said.
That was just the start of a catalog that now holds more than 100 , dinosaurs, birds of prey, cartoon characters and even a wedding announcement silhouette--all tucked away among microchip circuits. Davidson calls the collection the Silicon Zoo.
After Davidson found Waldo, he and others started enthusiastically tearing apart Hewlett-Packard workstations and Digital Equipment Corp.'s Vax minicomputers from to find more. And when Davidson posted the images online, chip designers started sending him new samples, often challenging him to find the artwork without telling him what it was. Now he has more than 300 chips with unusual micrographic imagery.
While the width of the Waldo image is just over half the diameter of a human hair, sizes vary widely, depending on artistic impulses and the ever-shrinking features made possible with more advanced chip manufacturing. The difficulty of finding them is commensurate. "Some are so big, it's like finding an automobile in a haystack. Some are so small, it's like finding a needle," Davidson said.
Davidson is a cell biology researcher at Florida State University, but he also does educational Web sites about microscopy under contract for microscope makers Nikon and Olympus. He also has micrographs of everything from beer to vitamin C.
The silicon chip images show a particular kind of technical aesthetic. For example, one of the images Davidson finds most impressive is of Thor, the Norse god of thunder--a comparatively large, square image measuring about 1 millimeter on edge of an HP chip. The picture is created out of a matrix of tiny dots, each one a "sunken via," or a tiny wire that connects one layer of a chip to a deeper layer.
But such artistic whimsy in some cases came with a cost, Davidson said.
"A lot of chip designers told me it was absolutely forbidden. Some of them lost their jobs doing this stuff," he said.
With the extensive scrutiny that today's chips undergo, it's now impossible to sneak in a doodle without corporate authorities knowing. "You put Dogbert on one of these chips, and they're going to notice," Davidson said.
Silicon artistry is a skill more than three decades old. The earliest known images in the Silicon Zoo are on Texas Instruments chips from the late 1960s or early 1970s, featuring a sailboat, the Apollo mission lunar lander and the U.S.S. Enterprise starship from the "Star Trek" TV series.
The most prolific practitioners of silicon artistry were at HP, in Davidson's opinion. "They had a competition going as to who could create the most complex art," he said.
Intel microchips, by contrast, have hardly any artwork. "The only thing we found was that shepherd on that dual-ported RAM controller," he said. In a visual-technical pun, the shepherd is overseeing a ram with two heads, symbolizing a chip that governs random access memory (RAM) with two communication channels.
Not all the discoveries have been artistic. On one chip, there's a rambling hodgepodge of nonsensical legal warnings. In another, a Vax chip from DEC, is a message in Russian for the would-be reverse engineers on the other side of the Iron Curtain trying to determine the chip's functions: "When you steal, steal from the best."
The artwork generally is benign for the chip's real job, but there are exceptions. One example is a cheetah incorporated into an HP memory controller chip. The problem came with the tiny bits of metal that depict the animal's spots.
"The little spots were falling out and causing short circuits," Davidson said. "That was causing production problems. They don't like that."
In another case, a Daffy Duck image caused problems during the chip verification process. To get around such problems, some images have tiny grounding wires, so they don't cause electrical problems with the rest of the chip, Davidson said.
Engineers still create silicon imagery, but it's becoming harder to appreciate, if not yet a lost art. Newer ways of mounting chips within electronics packages often require the chip to be flipped upside-down so that circuitry isn't visible--and prying the package apart is worse than opening up an Egyptian tomb to looters.
"Those we don't know about unless we get a wafer," or the circuitry-encrusted circular silicon crystal, before it's been sliced into rectangular chips, Davidson said. "It's almost impossible to recover it without serious damage."