October 2002

Data Extinction

Continued from page 3

By Claire Tristram

Emulation: Digital CPR

An even purer example of the problems associated with preserving digital objects is seen in the widespread attempt to keep arcade games like Joust and Asteroids playable today. Feinstein is keeping old games alive by preserving the machines that run them, but many others are trying a different means: hacks are importing the games onto today's PCs.

Such hacks use a technique called emulation, creating a program that simulates the registers (storage locations in the central processing unit) and behaviors of the old machine, and which can fool old games into thinking they are being run on old hardware. Emulation has the advantage of keeping the original bits of a given file or program intact, warts and all. "In porting, it's difficult to capture the bugs and idiosyncrasies of the original," says Jeff Vavasour, chief technical officer of Emeryville, CA-based Digital Eclipse, which is currently writing software to revive the original Joust and other arcade classics. "In games, that's important. So we don't port. We use emulation instead."

Indeed, emulation has been proposed as a way to keep not just games but everything else digital alive. It has its own drawbacks, however. "Emulation doesn't preserve, it just mimics," says Feinstein. "The timing will be all wrong. Or the sound will be off.... It's like the guy who reshot the film Psycho using Hitchcock's shot book. You recognize something of the original, but mostly you recognize how different it is from the original."

Looking for hard evidence to support claims like Vavasour's, that emulation is better at preserving digital content's original look and feel, Hedstrom and his colleague Cliff Lampeso at the University of Michigan recently organized one of the first studies to compare migrated and emulated versions of the same software. Subjects first spent an hour learning the maze game Chuckie Egg on its original platform, the BBC Micro, a microcomputer popular in Britain in the mid-1980s. They then played the game twice more on modern PCs, once with a version that had been migrated into a modern computer language and again with the original BBC Micro code running inside an emulator. Hedstrom and Lampeso found no statistically significant difference in the way the subjects rated the performance of the two versions. Says Hedstrom,"It was not apparent that emulation did a better job."

Nonetheless, some computer scientists have suggested "chains" of emulators as a temporary solution to the problem of digital obsolescence: as each generation of hardware grows obsolete, it will be replaced by a layer of emulation software. But it's an idea that has others shaking their heads. "It's extremely dangerous to talk about emulation as a solution," says David Bearman, president of Archives and Museum Informatics, a consulting group that works with business and government entities, helping them preserve digital files. "It gives an excuse to managers and governments around the world to put off doing things that really need to be done right now."