The Kindle Fire's dual-core processor was perfectly respectable when Amazon unveiled the tablet last fall. But now it's looking molasses-slow. What's changed in a few short months? The Nexus 7's quad-core CPU, the Nvidia Tegra 3, is to blame. Google's quad-core chip should deliver zippier multitasking, video-streaming, and Web browsing than the Fire's dual-core laggard. You can bet the next Fire will go quad-core too.