Intel Details Atom Z2760: Clovertrail for Windows 8 Tablets

For much of the past year we've been hearing that Intel's Atom for Windows 8 tablets is going to be the one to beat. Ivy Bridge (and later, Haswell) will exist at the high-end of the Windows 8 tablet space but if you want Intel's answer to ARM based Windows RT tablets it's going to come from the Atom lineup. It's still too early to talk about pricing, but expect Atom based Windows 8 tablets to exist in the sub-$600 space. Exactly how low they go will depend entirely on what the OEMs decide to ship at. My hope is for prices to start around $399 rather than much higher but we'll see just how seriously the Windows 8 OEMs are going to take this launch.

Intel's Atom for Windows 8 tablets has gone under the codename Clovertrail for quite some time. Today it gets official: the first Clovertrail SoC is Intel's Atom Z2760. Following similar naming to Medfield's Atom Z2460, there's a lot more that's shared between Clovertrail and its smartphone counterpart.

Similar to its approach with Medfield, Intel built a Windows 8/Clovertrail form factor reference design. The 8mm thick 10.1-inch tablet was built by a single ODM, but four manufacturers total are allowed to reuse those designs as they see fit. The FFRD approach isn't as necessary here as it was with Medfield because most of the traditional PC OEMs are already used to working with Intel. Given Intel's intense focus on driving platform power down however, building a reference design that others can follow makes a lot of sense. We'll actually see even more of this with Haswell next year.

From an availability standpoint we'll see the first Atom based Windows 8 tablets this fall. Intel announced design wins with Acer, ASUS, Dell, Fujitsu, HP, Lenovo, LG, Samsung and ZTE. The thinnest tablets will measure 8.5mm in thickness and weigh as little as 1.5 lbs. Not all Atom based Windows 8 tablets will be available on October 26th, but we'll see them starting a few weeks later.

Atom's big promise of course is ARM based tablet pricing with full x86 backwards compatibility, allowing the use of virtually all of your existing legacy Windows 7. It's a pretty compelling sell. If Intel can deliver the same (or better) performance/battery life compared to the ARM based Windows RT tablets, while preserving backwards compatibility Clovertrail would seem like a no-brainer. Simple solutions are rarely so simple, so we'll have to see this one play out in the market to be sure. Until then, we have some much needed architectural detail on Clovertrail and the Atom Z2760.

The Architecture

Clovertrail is the platform name, the single-chip SoC is called Cloverview. The architecture is very similar to Medfield's Penwell SoC. The most obvious differences are in the CPU and GPU configuration. Cloverview features two 32nm Saltwell Atom cores instead of one in Medfield/Penwell. These two cores run at up to 1.8GHz, a slightly lower clock speed compared to the Penwell that ships in Motorola's RAZR i. Each core has its own private 512KB L2 cache.

The GPU is a PowerVR SGX 545 from Imagination Technologies, clocked at a very high 533MHz. Direct3D feature level 9_3 is officially supported. Intel claims that the GPU is fed by a better engine in Clovertrail/Cloverview than it is in Medfield, however any additional details were impossible to come by.

The memory controller remains a dual-channel LPDDR2-800 design. Most tablets will see two 1GB devices populating the channels. Package on package (PoP) stacks will be used for DRAM and SoC integration, similar to what you see in a smartphone.

The other changes are more subtle. Video encode/decode is handled by IP licensed from Imagination Technologies, however the encoder is newer than what was used in Medfield. Clovertrail uses the same Silicon Hive ISP from Medfield. It supports two cameras (2MP/8MP) and burst mode.

The platform supports true connected standby, meaning Intel's new S0ix sleep states (similar to what was announced in Haswell). I realized I haven't yet detailed what these mean yet but in short on DC power you can expect polling roughly every 30 seconds for new data (incoming emails, tweets, etc...) delivering an experience somewhat similar to a smartphone. Off-SoC device drivers need to support Windows 8 run time power management (RTPM) to support these new low power sleep states. Intel claims that in its lowest platform sleep state (S0i3) the SoC's power consumption is below 2mW.

Connected standby is only currently supported by 32-bit Windows 8, so although Clovertrail supports x86-64 the platform will launch as 32-bit only. There's no support for alternate OSes at this point.

The SoC doesn't support SATA, just eMMC like most other smartphone/tablet SoCs. This is a bit of a disappointment as most eMMC controllers are pretty bad, but Intel tells us they've been working to improve things with the controllers that are out there.

There's no USB 3.0 support, Clovertrail just supports two USB 2.0 ports (OTG + xHCI, although OTG isn't supported by Windows 8). OEMs can obviously integrate hubs in any docking stations they may build.

On Pricing and ARM

Intel claims that there's no reason that Atom based Windows 8 tablets, from a hardware bill of materials perspective, should be any more expensive than their ARM based counterparts. The important takeaway is that Intel is significantly reducing the price of the Atom Z2760 due to competitive pressure from ARM. Most ARM smartphone SoCs seem to be priced in the $15 - $30 range, and I'd expect the Z2760 to fall somewhere in that range. Intel has shipped cheap CPUs in the past, but I don't know that they've ever shipped something this cheap. ARM's impact on Intel is measurable, it is the new AMD.

On Performance and Power

Microsoft isn't allowing any hands on performance of Windows 8/RT tablets yet so we don't have any of our own performance data to share. Intel did share some SPEC CPU2000 data it ran on its own with competing platforms. The data below wasn't generated by us so take it with a gigantic grain of salt:

Everything here is normalized to the performance of Qualcomm's Snapdragon S4 (dual-core Krait, 1.5GHz). Basically it shows a tangible advantage for Clovertrail. That's not too hard to believe given what we've seen in the phone space, although we'll have to wait and see once we get our hands on final hardware. Sunspider scores at or below 800ms should be possible as that's what we've seen on preproduction hardware already.

We've already established that Medfield is competitive from a power standpoint with ARM based SoCs. It doesn't offer the best power characteristics, but it's hardly the worst. Middle of the road is the best way to put it. We don't have (and aren't allowed to have) a Clovertrail based Windows 8 tablet yet, so we'll have to reserve full analysis until then. However, Intel did share some early data with us from its own testing that points to Clovertrail battery life being competitive with other platforms:

Intel standardized on 200 nits for all of its battery life tests, however I wasn't allowed to study/mirror the workloads and test procedure. The data looks good for Intel. Clovertrail's power consumption appears to be lower than NVIDIA's Tegra 3 and a little worse than Apple's iPad 2. This all looks quite plausible, I'm curious to see how power consumption would compare in Intel's tests to Qualcomm's S4. We'll find out for ourselves in due time.

Final Words

Intel was pretty light on Clovertrail details other than what we've published here. The real work begins once we start getting hardware late next month. The biggest question is really whether or not the OEMs will get pricing right for these tablets. An affordably priced Windows 8 tablet running Clovertrail can be very compelling for someone looking to carry a single device instead of a tablet + notebook. As with most things however, I am worried that we'll have to wait at least one more generation for perfection. I can't tell if I'm being cynical or realistic. Let's hope I'm surprised come October 26th.