When I wrote my first article on Intel's Atom architecture I called it The Journey Begins. I did so because while Atom has made a nice home in netbooks over the years, it was Intel's smartphone aspirations that would make or break the product. And the version of Atom that was suitable for smartphone use was two years away.

Time sure does fly. Today Intel is finally unveiling its first Atom processors for smartphones and tablets. Welcome to Moorestown.

Craig & Paul’s Excellent Adventure

Six years ago Intel’s management canned a project called Tejas. It was destined to be another multi-GHz screamer, but concerns over power consumption kept it from coming to fruition. Intel instead focused on its new Core architecture that eventually led to the CPUs we know and love today (Nehalem, Lynnfield, Arrandale, Gulftown, etc...).

When a project gets cancelled, it wreaks havoc on the design team. They live and breathe that architecture for years of their lives. To not see it through to fruition is depressing. But Intel’s teams are usually resilient, as is evidenced by another team that worked on a canceled T-project.

The Tejas team in, er, Texas was quickly tasked with coming up with the exact opposite of the chip they had just worked on: an extremely low power core for use in some sort of a mobile device (it actually started as a low power core as a part of a many core x86 CPU, but the many core project got moved elsewhere before the end of 2004). A small group of engineers were first asked to find out whether or not Intel could reuse any existing architectures in the design of this ultra low power mobile CPU. The answer quickly came back as a no and work began on what was known as the Bonnell core.

No one knew what the Bonnell core would be used in, just that it was going to be portable. Remember this was 2004 and back then the smartphone revolution was far from taking over. Intel’s management felt that people were either going to carry around some sort of mobile internet device or an evolution of the smartphone. Given the somewhat conflicting design goals of those two devices, the design team in Austin had to focus on only one for the first implementation of the Bonnell core.

In 2005, Intel directed the team to go after mobile internet devices first. The smartphone version would follow. Many would argue that it was the wrong choice, after all, when was the last time you bought a MID? Hindsight is 20/20 and back then the future wasn’t so clear. Not to mention that shooting for a mobile extension of the PC was a far safer bet for a PC microprocessor company than going after the smartphone space. Add in the fact that Intel already had a smartphone application processor division (XScale) at the time and going the MID route made a lot of sense.

The team had to make an ultra low power chip for use in handheld PCs by 2008. The power target? Roughly 0.5W.

Climbing Bonnell

An existing design wouldn’t suffice, so the Austin team lead by Belli Kuttanna (former Sun and Motorola chip designer) started with the most basic of architectures: a single-issue, in-order core. The team iterated from there, increasing performance and power consumption until their internal targets were met.

In order architectures, as you may remember, have to execute instructions in the order they’re decoded. This works fine for low latency math operations but instructions that need data from memory will stall the pipeline and severely reduce performance. It’s like not being able to drive around a stopped car. Out of order architectures let you schedule around memory dependent operations so you can mask some of the latency to memory and generally improve performance. Despite what order you execute instructions, they all must complete in the program’s intended order. Dealing with this complexity costs additional die area and power. It’s worth it in the long run as we’ve seen. All Intel CPUs since the Pentium Pro have been wide (3 - 4 issue), out of order cores, but they also have had much higher power budgets.

As I mentioned in my original Atom article in 2008 Intel was committed to using in order cores for this family for the next 5 years. It’s safe to assume that at some point, when transistor geometries get small enough, we’ll see Intel revisit this fundamental architectural decision. In fact, ARM has already gone out of order with its Cortex A9 CPU.

The Bonnell design was the first to implement Intel’s 2 for 1 rule. Any feature included in the core had to increase performance by 2% for every 1% increase in power consumption. That design philosophy has since been embraced by the entire company. Nehalem was the first to implement the 2 for 1 rule on the desktop.

What emerged was a dual issue, in-order architecture. The first of its kind from Intel since the original Pentium microprocessor. Intel has learned a great deal since 1993, so reinventing the Pentium came with some obvious enhancements.

The easiest was SMT, or as most know it: Hyper Threading. Five years ago we were still arguing about the merits of single vs. dual core processors, today virtually all workloads are at least somewhat multithreaded. SMT vastly improves efficiency if you have multithreaded code, so Hyper Threading was a definite shoe in.

Other enhancements include Safe Instruction Recognition (SIR) and macro-op execution. SIR allows conditional out of order execution depending if the right group of instructions appear. Macro-op execution, on the other hand, fuses x86 instructions that perform related ops (e.g. load-op-store, load-op-execute) so they go down the pipeline together rather than independently. This increases the effective width of the machine and improves performance (as well as power efficiency).

Features like hardware prefetchers are present in Bonnell but absent from the original Pentium. And the caches are highly power optimized.

Bonnell refers to the core itself, but when paired with an L2 cache and FSB interface it became Silverthorne - the CPU in the original Atom. For more detail on the Atom architecture be sure to look at my original article.

The World Changes, MIDs Ahead of Their Time
POST A COMMENT

67 Comments

View All Comments

  • teohhanhui - Thursday, May 06, 2010 - link

    But they'll be showcasing it on their Moblin/Meego which is Linux. Won't shoot themselves in the feet, will they? Reply
  • rahvin - Thursday, May 06, 2010 - link

    And if it only runs on Moblin, only with specific kernel versions, uses a binary blob driver and isn't maintained it will be the same story as GMA500 all over again. Reply
  • strikeback03 - Thursday, May 06, 2010 - link

    As pointed out, plenty of other Android phones are using the same graphics. And I haven't heard a lot of complaints about lack of drivers for the Droid/N1/etc. Reply
  • elisha.pan - Wednesday, May 05, 2010 - link

    GMA500 has nothing with the Intel GMA series, but name. It is exactly the same with PowerVR SGX 535. Reply
  • DanNeely - Wednesday, May 05, 2010 - link

    This is the same GPU used in almost every other smart phone on the market, except that it's designed to be clocked up to twice as fast. It's not going to run Crysis *rolls eyes* but it's more than capable of doing everything a smart phone/internet tablet will need to do. Reply
  • ekul - Wednesday, May 05, 2010 - link

    exactly. without open source drivers for the graphic any development of meego outside of intel will never go anywhere. One of the reasons I bought my current netbook is the gma 950 has excellent open source drivers that just work.

    Open source development moves fast. Closed source binaries get left behind because they can't keep up with the release schedule. The current gma 500 drivers already need a kernel several versions old as well as an old X server. How many releases is meego going to miss?
    Reply
  • ViRGE - Wednesday, May 05, 2010 - link

    I can see why Anand thinks it's an interesting product, but based on his article I don't think Intel is quite there.

    The current need for 5 chips is going to be a problem no matter how Intel dresses things up, and if all phones end up looking like the design shown I wouldn't be surprised if the consumer reaction was tepid - a phone of that size is still pretty big. The video playback time is also going to be a problem when it comes to spec sheets (I doubt the real-world impact will be as huge), but OEMs like their spec sheets and consumers aren't too far off either. Just looking like it'll perform poorly there may be enough.

    The other issue is the reliance on an OS. At this point it seems like no one really wants another OS. Most people around here seemed to be more relieved than concerned when Palm went under. With BlackBerryOS, IPhoneOS, Android, and WinCE, there seems to be as many OSes as the market can reasonably handle. Moblin/MeeGo may be necessary for the hardware right now, but I see no reason to expect that it's going to be properly developed for consumer use like the above OSes were. Unless Intel can land RIM/Apple, they need to get Android up to par on Moorestown and they need to do it yesterday.

    Ultimately I think it's going to Medfield that's a proper ARM competitor. With fewer chips it will fit in to traditional designs, and with any luck Intel will be a node ahead of its competition on the manufacturing process. It won't solve the current OS reliance, but it'll put them in a better position than Moorestown does.
    Reply
  • ET - Wednesday, May 05, 2010 - link

    Ultimately I think that most people don't care about the OS. The OS mainly matters in terms of applications available for it, and it's a pain for developers to address many OS's, but also an opportunity for new developers to carve their niche.

    That said, Anand did mention that Intel is making Android available for this new platform, which should be good enough.
    Reply
  • IntelUser2000 - Wednesday, May 05, 2010 - link

    It's much closer than expected. There were quite frequent comments that thought it wouldn't even reach 5 hour on standby! Having a lot of knowledge and doing a bit research helps of course. Glad they can be roughly on par though.

    It's likely the idle power can't be achieved without optimized OSes. Even if you can run Windows on it, what's the point when you won't have the battery life for it? Windows uses too much on keeping legacy support and its too bloated for idle power under 50mW.

    Platform approach is the key to low power on Moorestown.
    Reply
  • piroroadkill - Wednesday, May 05, 2010 - link

    I'm not sold. ARM has been more efficient for a lot longer, even though it's still being made on commonly larger processes than current Intel CPUs. All smartphones are ARM anyhow, so I don't see the advantage in having x86 in this space Reply

Log in

Don't have an account? Sign up now