Computer Gaming Hardware

It is important to know that there are two flavors of Atom CPUs. Atom series 2xx and N2xx (at this publishing only 230 and N270 models were available) – codenamed “Diamondville” – are targeted to laptops (because they use chipsets from Intel 945 series, which are big and use two chips) while Atom series Z5xx – codenamed “Silverthorne” – are targeted to handheld devices with internet access, not only because they use a new chipset called US15W, which is very small and uses only one chip, but also because Atom Z5xx are physically smaller than other Atom CPUs (14 x 13 mm against 22 x 22 mm).
You may also hear references to the Centrino Atom platform (codenamed “Menlow”). This platform consists of an Atom CPU, the new US15W chipset (codenamed “Poulsbo”) and radio capability. Atom has a 16-stage pipeline, which is a little bit longer than current Core 2 CPUs. This was done for some reasons. First, this allows a better power efficiency. More stages means more units, which can be spread across the chip and thus better spreading heat production, instead of having fewer units which would concentrate heat on a single point. With more units the probability of having some of them idle is higher compared to a CPU with fewer units, meaning that they can be turned off for power savings. Another advantage in a longer pipeline is that the micro architecture can achieve higher clock rates. The reason why is that each unit will have fewer transistors, making it easier to pump clock rate.
Another feature found on Atom is a true 128-bit internal data path, feature introduced with processors based on Core micro architecture (e.g. Core 2 Duo). On previous CPUs the internal data path was of 64 bits only. This was a problem for SSE instructions, since SSE registers, called XMM, are 128-bit long. So, when executing an instruction that manipulated a 128-bit data, this operation had to be broke down into two 64-bit operations. The 128-bit internal data path makes Atom faster to process SSE instructions that manipulate 128-bit data. Intel calls this feature “Digital Media Boost”.
Atom can disable a portion of its L2 cache size when entering C4 or C4E states, feature known as “Dynamic Cache Sizing” (Atom 2xx does not support C4 mode and thus doesn’t have this feature). Usually when the CPU enters the C4 state the memory cache is fully turned on, and under C4E state the memory cache is fully turned off.
Another traditional power-saving feature available on Atom CPUs (except models 2xx) is Enhanced Speed Step technology. This technology makes the CPU to run at lower clock rates and lower voltages when you are running a program that isn’t demanding the CPU full processing power.
Since Intel 945 chipsets use two relatively big chips, CPUs using these chipsets are targeted to laptops only, as they can’t fit the small footprint required for smaller applications. In theory any Intel 945 chipset can be used, but Intel recommends the mobile version and you will probably see products with Intel 945GSE, which is the chipset recommended for the “NetBook’08” platform. All memory and I/O features for a small laptop based on Atom CPU will depend on the chipset used.