Linux kernel runs inside web browser

JavaScript mimics 486 PC

An independent programmer has used JavaScript to build a PC emulator capable of running Linux inside a web browser.

French hacker Fabrice Bellard says his JavaScript PC Emulator can run the 2.6.20 Linux kernel inside Mozilla's Firefox 4 and Google's Chrome 11, two browsers designed to significantly advance JavaScript speeds. "I did it for fun, just because newer JavaScript engines are fast enough to do complicated things," Belllard writes. But he believes the emulator could be used to benchmark JavaScript engines.

According to Bellard – known for creating the FFmpeg open source multimedia project and the QEMU processor emulator – his JavaScript PC emulator is about two times slower on Chrome's V8 JavaScript engine than on Firefox's Jaeger Monkey engine, and this was promptly seized upon by JavaScript creator Brenden Eich, who's now the chief technology officer at Mozilla. Bellard tested the 32-bit version of both browsers.

Douglas Crockford - the man who "discovered" JSON and now servers as senior JavaScript architect at Yahoo! – recently released a new JavaScript benchmark based on JSLint, his own JavaScript code quality tool. Firefox 4 bested Chrome on this test too, as did Microsoft's Internet Explorer 10 preview.

Fabrice Bellard wrote his PC Emulator with pure JavaScript using the typed array specification, which provides an API for using native binary data, and he has tested his creation on browsers running atop Linux, Windows, and Mac OS.

The emulated hardware includes a 32-bit x86 compatible CPU, a 8259 programmable interrupt controller, a 8254 programmable interrupt timer, and a 16450 UART (universal asynchronous receiver/transmitter). According to Bellard, the emulated CPU is comparable to an Intel 486 chip, though it does not include a floating point unit. Bellard was able to emulate a floating point unit, however, using the Linux kernel.

Bellard believes his emulator could be used for client-side cryptographic processing. Or – if you're looking for a more serious pursuit – he also points out it could eventually let you play old DOS games. ®

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