Since Android uses the Davlik virtual machine for running applications, most Android applications can run on an Android phone of any architecture, whether it be ARM or x86, or even MIPS. However applications that include native code—such as Firefox—need to be compiled separately for each platform that needs to be supported.
This means that till now, Firefox has only been available for Android for ARM, and more specifically, ARMv7, which still leaves out millions of devices that use different architectures. Recently Mozilla added official support for phones using the ARMv6 architecture—as long as they met the minimal requirement of an 800Mhz processor and 512MB RAM—which is already used by a large number of Android phones, the majority in fact.
Mozilla has plans to make builds of Firefox available for x86-based Android phones. There are however, very few mobile devices based on the x86 architecture. The bigger benefit—at laeast as of now—of Firefox for Android being available for x86 is that now it is much easier and faster to run it on an emulator on a PC. Recent vesions of Android have been available as x86 images so that they can run much better on desktop hardware, which is generally x86-based as well.
You can read more about the availability of Firefox for Android x86 on Mark Finkle’s blog where you will also find a link to download the latest nightly build.
