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The range of mobile devices on the market is constantly increasing and has until now been dictated by ARM micro-architecture (RISC) - for example, the X-Scale processors that are found in PDAs or in the iPhone. Intel wants to use the Atom processor with x86 architecture to break into that same ARM market.
The Atom micro-architecture is completely different from that of the Core 2 or the AMD64. It was a completely new design by Intel, intended mainly keep power consumption and manufacturing costs very low — raw frequency plays a much less important role here.
The technology used in the Atom is known as “in order micro-architecture” and supports both 32 bit and 64 bit applications. The familiar speculative execution function has not been implemented here due to the high number of transistors this requires, and the corresponding increase in energy draw. Thus the architecture processes all commands one after another which means that the instructions per cycle (IPC) figure is not very high. The L1 cache is also set up differently; the Conroe micro-architecture has two 32 kB caches, whereas the Atom has a 32 kB instruction cache and a 24 kB write back cache.
The Atom processor only has one core, so Intel has reintroduced Hyper-Threading technology in order to ensure that it is used optimally, which means the processor has two logical processors. Thus, for some applications that are multi-core-capable, you can achieve better speeds using the single core. This also makes the operating system (such as Windows XP or Vista) considerably faster to react to commands.
The Atom micro-architecture covers almost all of the current command extensions: MMX, SSE, SSE2, SSE3 and SSSE3. Virtualization technology is also already available for some models.