Intel's Ultra-Portable Atom: Unveiled

by Guest Sat Jun 07, 2008 2:36 am

Do you remember the original Pentium 4? It launched at 1.5 GHz and gave us our first bittersweet taste of the NetBurst microarchitecture, which Intel would use to replace the P6 design.

When the Pentium 4 began its life, Intel manufactured the chips on a 180 nm node. The 42 million transistors that went into those first Pentium 4s - internally referred to as Willamettes - occupied a die no less than 217 square millimeters. Keep those figures in mind throughout our overview of Intel’s newest mobile processor and platform. And don’t feel too old; eight years seems like a lifetime, when you’re talking tech.

<table id=table5 width="100%" align=left border=0><tr><td bgColor=#f0f0f0>Mobility, Redefined</TD></TR>
<tr><td bgColor=#000080>Smaller than a Laptop</TD></TR></TABLE>

Intel is formally announcing a brand new processor today that it hopes will drive the next generation of mobile Internet devices. Perhaps you’re already familiar with the MID concept. Last year, Intel took the wraps off of its McCaslin platform, a seldom-discussed proof-of-concept that never really took off. Nor was it meant to. McCaslin employed Intel’s A100/A110 processor built on 90nm process technology. Those CPUs were derived from Intel’s Pentium M efforts. And while they enabled respectable compute muscle at 3W, imagine running Windows Vista on an 800 MHz desktop. Or don’t. It’s a painful thought. Nevertheless, the A100 and A110 are x86 Intel chips that go into real products, like Samsung’s Q1.

Intel's Ultra-Portable Atom: Unveiled Atom_slide_1

Menlow takes Intel's MID concept from ultra-portable notebooks to pocket-sized devices falling into four different sub-categories.

The MID market is now being broken up into several different categories, including portable navigation, Internet tablets, video players, and handheld gaming. Note the absence of voice communications. Intel has its eye on smartphones, but the current hardware foundation isn’t there yet. We’ll have to wait until 2009/2010 to see what the Apples and Googles of the world do with Intel’s hardware vision. For now, it’s all about adding Internet connectivity to the digital devices you might already tote around with you.

“Big deal,” you say. “The Q1 you just mentioned has Wi-Fi access and works with Samsung’s HSPDA modem. My PSP does Wi-Fi. And I don’t mind loading my Archos video player up with hours of content before I hit the road.” All true. However, you’re still faced with several obstacles. The 800 MHz A110 in that Q1 isn’t very beefy. Although it centers on Intel’s mobile technology, a reported three hours of battery life isn’t exactly stunning. And between all three of the examples posited, you have the issue of compatibility to address.

Intel's Ultra-Portable Atom: Unveiled Atom_slide_2

The Menlow platform, now known as Centrino Atom, represents Intel's first ground-up low-power CPU/chipset combination, setting the stage for Moorestown in 2009.

Here’s where Intel’s story gets a bit more compelling. You probably didn’t know this, but Adobe has 160 versions of Flash 7.2 it uses to support the many combinations of mobile devices with different ARM processors and versions of the software stack. The company has to keep creating new versions at the cost of both time and money. Of course, Adobe charges its customers for the development efforts. For Intel’s MIDs, however, Adobe can port its software one time and any derivative hardware platform will use the code. The same goes for audio and video codecs, which can already be a pain when dealing with today’s fragmented portable entertainment device business.

The idea here, according to Pankaj Kedia, director of Intel’s global ecosystem programs, is to make the Internet available wherever you are, rather than have you going to it. Put it in the context of cell phones. Instead of being tied to land lines, cell phones provide the freedom of voice communications wherever you happen to be. Intel’s Kedia sees the same thing happening with the Internet. Rather than searching for somewhere to hook up, MIDs will put the Internet in your pocket with all of the compatibility and performance of a PC. It’s a noble vision for sure, and we haven’t yet heard how all of these devices will achieve ubiquitous connectivity. However, one thing is for sure: the hardware is here and it makes the old McCaslin platform look like child’s play.

by Guest Sat Jun 07, 2008 2:37 am

<table id=table5 width="100%" border=0><tr><td bgColor=#f0f0f0>Meet Centrino Atom</TD></TR>
<tr><td bgColor=#000080>A Processor, Chipset, Wireless Radio, and Pocket-Sized Package</TD></TR></TABLE>

Intel’s new platform for MIDs is called Menlow. And whereas McCaslin was found in ultra low-voltage notebooks, Menlow is the processor and chipset combination you’ll find in navigation devices, Internet tablets, video players, and gaming handhelds. From here on out you won’t hear Intel calling the platform by its internal name, though. The official brand is Centrino Atom.

A complete Centrino Atom configuration consists of the Atom processor (more on that shortly), Poulsbo, the single-component chipset, a wireless device, a battery, and a small form factor enclosure.

Intel's Ultra-Portable Atom: Unveiled Atom_slide_3

Intel considers Centrino Atom its first-generation MID solution. It'll follow up with Moorestown, targeting the lucrative smartphone market, in the 2009/2010 time frame.

Centrino Atom sits between two other Intel brands. At the entry-level, you’ll find netbooks and nettops powered by Atom. Those are small, simple, and affordable devices built for Internet-oriented usage models. At the high-end, Intel has its Centrino initiative driven by Core 2 Duo processors. Centrino Atom is shooting for the “best Internet experience in your pocket.”

<table id=table5 width="100%" border=0><tr><td bgColor=#f0f0f0>The Atom Processor</TD></TR>
<tr><td bgColor=#000080>Making Portable Possible</TD></TR></TABLE>

Formerly known as Silverthorne, Intel’s Atom processor leverages the 45nm high-K process technology we’ve come to associate with Penryn-based desktop and workstation CPUs. Remember the Pentium 4 we mentioned earlier? Atom sports 47 million transistors—just 5 million more than the original Pentium 4. But whereas Willamette occupied more than 200 square millimeters, Atom fits in less than 25 square millimeters.

Intel's Ultra-Portable Atom: Unveiled Atom_slide_4

Positioned squarely between the Atom (Diamondville) nettops and Centrino (Core 2 Duo) notebooks, Centrino Atom now defines Intel's MID segment.

Intel gave us access to the principal architect of Atom, Belliappa Kuttanna, who explained that one of his goals was to drastically reduce power consumption in order to propel Intel into a new market segment. Thus, Atom isn’t derived from any existing microarchitecture. That’s a big differentiator from the A100-series, which did center on Intel’s mobile designs. A second objective was to infuse Atom with enough processing horsepower to drive modern operating systems like Vista. Thirdly, Atom needed to be scalable, giving Intel the flexibility to create an entire product family with different features and running at different speeds.

So, Kuttanna’s team had to start from scratch in building Atom. Right away, they adopted an in-order execution engine, meaning instructions are dispatched and executed in the order that they appear. With the exception of Intel’s Itanium processor, all of the company’s other designs employ out-of-order engines. While OOO execution generally improves performance, Kuttanna clarified that Atom’s in-order implementation yielded much better energy efficiency.

Intel's Ultra-Portable Atom: Unveiled Atom_slide_5

Positioned squarely between the Atom (Diamondville) nettops and Centrino (Core 2 Duo) notebooks, Centrino Atom now defines Intel's MID segment.

The Atom architects also started with a single-issue machine, but that didn’t meet the team’s performance requirements, so they eventually settled on a dual decode and issue machine with a number of optimizations aimed at simplifying the architecture. For instance, the 32KB L1 instruction cache features pre-decode extensions. Because the IA architecture has variable-length instructions, Atom uses an algorithm that’s able to tag instructions with an end-of-instruction marker after a pass through the decoder. The next time the instruction is fetched, you have an indication of where the instruction ends, yielding better performance through the decoder. Atom’s branch predictors are much simpler as well, since they’d otherwise eat up too much of the power budget. The take-away is that Intel made some sweeping changes to the way IA instructions are decoded in an effort to maximize decoder efficiency and reduce power consumption.

Atom is also the first processor since Intel’s Pentium 4 to feature simultaneous multi-threading (SMT) in the form of Hyper-Threading. By design, in-order execution engines spend more processor clocks to execute instructions. Normally that’d be a performance inhibitor. However, Intel saw opportunity there. When execution is stalled, say, waiting for memory, pipeline resources go unutilized. By adding SMT, performance goes up as a second thread keeps instructions flowing through the engine. According to Intel’s Kuttanna, the performance gains seen from Atom’s in-order architecture with SMT are higher than an out-of-order design. Of course, realizing the benefits of SMT on an Atom-based device requires threaded software. The good news is that many audio and video codecs are already coded to employ threaded architectures. Multi-tasking will also showcase Atom’s ability to juggle more than one thread.

Intel's Ultra-Portable Atom: Unveiled Atom_slide_6

Details of Atom's microarchitecture, unveiled at last.

Moving into the FP/SIMD execution clusters, Atom features two single-cycle SIMD ALUs, one of which is equipped with a shuffle unit. The other supports a full-width floating point adder for single precision FP adds. Why the emphases on SIMD performance in the execution cluster? In profiling the apps typical of an MID, it became clear to Intel’s team that it’d see significant gains from building a wide data path.

In addition to its 32KB instruction cache, Atom sports a 24KB writeback data cache. The memory execution cluster also boasts a dual-level TLB hierarchy - one buffer is smaller, allowing very low latency access, and the other is significantly larger. A 512KB L2 cache with ECC support is integrated as well, able to fetch 64-byte cache lines in two clocks (that’s 256 bits per access). Onboard hardware prefetchers either pull data from memory into the L2 cache or from the L2 cache into the data cache. The processing core consists of roughly 13 million transistors and the chip’s L2 cache takes up about 30 million transistors.

Despite its ground-up design, Atom maintains compatibility with Intel’s Core 2 Duo product lineup. The architecture supports Intel Virtualization Technology, Execute Disable Bit support, 64-bit extensions and SSE3. However, Intel’s Pankaj Kedia says that not every feature will be productized in every SKU