Intel Atom

Intel Atom is the brand name for a line of x86 and x86-64 CPUs (or microprocessors) from Intel, previously code-named Silverthorne and Diamondville processors, designed for a 45 nm CMOS process and intended for use in ultra-mobile PCs, smart phone and other portable and low-power applications.

Background
Prior to the announcement, outside sources had speculated that Silverthorne would have competed with AMD's Geode system-on-a-chip processors, currently used by the One Laptop per Child project, and other cost- and power-sensitive applications for x86 architecture processors. However, Intel revealed on October 15, 2007[1] that it is developing another new mobile processor, codenamed Diamondville, for OLPC-type devices.

Silverthorne will be sold under the brand name "Atom", while the formerly code-named Menlow platform it sits on will be sold under the brand name Centrino Atom.[2] Intel's Atom press release only mentions "Diamondville" once and seems to imply that it too will be named "Atom".[3] This seems to strengthen speculation that Diamondville is simply a lower-cost, higher-yielding version of Silverthorne with slightly higher TDPs at slightly lower clock speeds.[4]

At Spring Intel Developer Forum (IDF) 2008 in Shanghai, Intel officially announced that Silverthorne and Diamondville are based on the same microarchitecture. Silverthorne will be called the Atom Z series and Diamondville will be called the Atom N series. The more expensive lower-power Silverthorne parts will be used in Intel Mobile Internet Devices (MIDs) whereas Diamondville will be used in low-cost desktop and notebooks. Several Mini-ITX motherboard samples have also been revealed.[5] Intel and Lenovo also jointly announced an Atom powered MID called the IdeaPad U8.[6] The IdeaPad U8 weighs a mere 280g and has a 4.8" touchscreen providing better portability than a netbook PC and easier Internet viewing than a mobile phone or PDA.

In April 2008, an MID development kit was announced by Sophia Systems[7] and the first board called CoreExpress was revealed by a German company Lippert.[8][9] Intel offers Atom based motherboards.[10][11]

Availability
Atom processors became available to system manufacturers in 2008. Atom processors are not yet available to home users or system builders, although they may be obtained preinstalled on some ITX motherboards. The Diamondville Atom is used in the Acer Aspire One and MSI Wind PC netbooks.

Architecture
Intel Atom can execute up to two instructions per cycle (similar to the 1993 Pentium). Atom implements the x86 (IA-32) instruction set; x86-64 is so far only activated for the Atom 230 and 330 desktop models. N and Z series Atom models cannot run x86-64 code.[12] Like many other designs it divides certain x86-instructions into simpler internal operations prior to execution[citation needed], but to a significantly lesser extent (only ~4%) than in the Intel P6 (microarchitecture) and NetBurst families[citation needed]. In the Atom, internal μ-ops can contain both a memory load and a memory store in connection with an ALU operation, thus being more similar to the x86 level and more powerful than the μ-ops used in previous designs[citation needed]. This enables relatively good performance with only two integer ALUs, and without any instruction reordering, speculative execution, or register renaming. Atom therefore represents a partial revival of the principles used in earlier Intel designs such as Intel P5 and the i486, with the sole purpose of enhancing the performance per watt ratio.

It has been speculated that the die space used to perform x86-decoding will put the Atom design at a disadvantage compared to other mobile architectures, such as the ARM architecture.[13] The Moorestown platform which is the successor of the Menlow Platform will be a system-on-a-chip design that uses half the power of a Silverthorne processor. The reduced power consumption will make the platform more desirable for use in smartphones and other mobile internet devices.

Power requirements
While the Atom processor itself is relatively power efficient for an x86 instruction set chip, the chipsets used with it are currently not as power efficient. For example while the N270 chip itself has a maximum TDP of 2.5 W, the Intel Atom platform with the 945GSE Express chipset has a specified maximum TDP of 11.8 W, with the processor only making up a relatively small portion of the total power. Individual figures are 2.5W for the N270 processor, 6W for the 945GSE chipset and 3.3W for the 82801GBM I/O controller.[22][23][24][25] Intel also provides the Intel System Controller Hub US15W chipset with a TDP of less than 5W for the Atom processor Z5xx series.

Future
The next generation of the Atom, "Lincroft," architecture will be launched in 2H 2009 and is code-named Pineview. It will be used in Netbook/Nettop systems, and feature a system-on-chip (SOC) with an integrated single-channel DDR2 memory controller and an integrated graphics core. Pineview, like Diamondville, will be available in single and dual-core versions. It will feature HyperThreading, and is to be manufactured on a 45nm[26] or 32 nm [27] process.

Intel CEO Paul Otellini has stated that, along with other improvements, Atom (specifically Silverthorne) will shrink to the 32 nm process in 2009.[28] It has been suggested that the Atom will be the first Intel chip to transition to 32 nm due to its small size and low complexity.[29]

Competition
Nvidia launched its Tegra line of processors in June 2008. The performance and power consumption of the Tegra processor is claimed to be better than Intel's Atom[30]. The Nvidia's Tegra CPU offering is based on the ARM RISC architecture, which uses a different instruction set from the x86-32 bit and AMD 64. Because it does not use the same instruction set, programs will have to be compiled specifically for the Tegra processor in order for them to work on it. However, ARM is frequently used in handheld devices, such as PDAs, GPS systems, cell phones, and game systems such as the Nintendo DS. The VIA C7/Nano series is slightly above the average thermal envelope of the Atom, but has hardware AES support, out-of-order execution for the Nano (C7 is an in-order architechture), hardware random number generators. Performance comparisons of the Intel Atom against the Via Nano come to differing conclusions depending on the specific test case and depending which processor from the family is compared. In general terms a single core Intel Atom is outperformed by the Via Nano which is in turn outperformed by a dual core Intel Atom.