On Thursday, ARM took the wraps off its long awaited 64-bit version of the ARM instruction set architecture (ISA). Called ARMv8, the new extensions will put ARM squarely in competition with Intel in the server and desktop markets. It’s important to note that ARM’s move to 64 bits isn’t about performance - rather, it’s strictly about giving ARM-based platforms the ability to cleanly and efficiently address more than 4GB of usable memory.
In exchange for 64-bit support, ARM will be giving up a bit of power efficiency, which indicates that the initial batch of chips based on ARMv8 will be targeted not a mobiles but at the aforementioned servers and desktops.
The main mobile application for 64-bit ARM will be the forthcoming ARM-based Windows tablets. Neither Microsoft nor its third-party developers will want to have a 32-bit/64-bit split between its desktop and tablet OS, so the Windows ARM port will be 64-bit from the start. Indeed, it’s likely that ARM’s commitment to announcing a 64-bit version of its architecture was necessary before Microsoft even agreed to the Windows port.