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Cedar Trail Platform and Cedarview CPU

Released in 2008, the first generation of Atom CPUs did not have an integrated graphics core and worked together with a dual-piece chipset connected to the CPU via a quad-pumped FSB. At that time this meant that the energy-efficient CPUs with Bonnell microarchitecture existed within the standard infrastructure of i945 chipsets with GMA 950 and memory controller integrated into the North Bridge. And that was one of the weakest spots of the original concept: there were no specialized energy-efficient chipsets designed specifically for the Atom whereas the existing chipsets were comparable to the CPU itself in their power consumption and heat dissipation, making the resulting configurations not as economical as they might have been.

The developer was fully aware of this shortcoming, so the second version of the Atom platform, codenamed Pine Trail, had a completely different design. The graphics core was moved into the CPU and, under the new name of GMA 3150, was adapted for economical computers. The memory controller, now endowed with DDR3 SDRAM support, moved into the CPU as well. The conventional chipset was replaced with a specialized single-piece I/O hub NM10 which had a very low power draw and was connected to the CPU via a DMI bus. The power consumption and heat dissipation of the resulting platform were much better even though Intel had ventured to increase the clock rates of the second-generation Atoms a little.

Being far more attractive as a solution for small computers, the new platform gained widespread recognition but the general trend towards miniaturization and the developer’s desire to bring the Atom to tablet PCs and smartphones called for the Bonnell microarchitecture and for the platform at large to get even more economical. That’s why the third generation was soon conceived under the codename of Cedar Trail.

This time around, they couldn’t limit themselves to simply rearranging CPU and chipset components. All global changes that one could do to the platform had already been done. The chipset is anyway merged with the CPU on a single semiconductor die in such compact solutions. Therefore, the Cedar Trail platform, being oriented at netbooks and nettops, has the same structure as its predecessor Pine Trail and is even accompanied by the same I/O hub NM10 thanks to the latter’s low TDP of only 2.1 watts.

It is the Cedarview CPU we should turn to in order to find some innovations. The Bonnell microarchitecture has basically remained intact but progressed to a more advanced manufacturing technology. The Pineview series, like the earlier Atoms, were manufactured on 45nm tech process which can’t be expected to produce energy-efficient CPUs anymore, so the Cedarview is made of 32nm dies. The die shrink naturally leads to two advantages: lower heat dissipation and higher clock rates. While the senior models of the Pineview-based Atoms were clocked at 1.83 GHz, dissipating up to 13 watts, the Cedarview series can be clocked as high as 2.13 GHz, its TDP being as low as 10 watts.

Besides the new manufacturing technology, Intel tried to get rid of every bottleneck in the CPU design, one of which was the integrated graphics core. The success of the Nvidia ION and AMD Brazos platforms made it clear that users of small and low-power systems were interested in being able to play high-definition video, the capability which was missing with the Pine Trail. So now the Cedarview’s graphics core supports hardware decoding of HD video in AVC/H.264, VC1/WMV9 and MPEG-2 formats.

This is the consequence of Intel’s new approach to integrated graphics in its Atom CPUs. Although formally known as GMA 3600, the graphics core is in fact the PowerVR SGX 545 GPU licensed from Imagination Technologies. So, instead of Intel’s own solution, the new Atoms are equipped with a third-party GPU which, by the way, is often employed in mobile CPUs with the ARM architecture.

The benefits of this approach are obvious. Intel’s modern HD Graphics series are fast and functional solutions but cannot suit the Atom with their power consumption specs. As for the GMA series which used to be integrated into the earlier Atom CPUs, those are too slow and not compatible with up-to-date DirectX versions. Moreover, they offer no hardware acceleration for video playback. The PowerVR SGX, on its part, is quite economical and meets today’s functional requirements. It is faster than the GMA 3150, supports DirectX 10 and can decode HD video in popular formats. It seems to be a good match to the Atom series, at least in theory.

This third-party graphics core has been enhanced by Intel in terms of monitor support. The earlier Atom CPUs used to support high resolutions only with analog video interface, but now DVI, HDMI and DisplayPort are all supported, too. Moreover, the integrated graphics core can output two separate images to two monitors concurrently.

The Atoms have improved in some other respects, too. For example, the Cedarview can boast an enhanced memory controller. Although still single-channel, it can work with DDR3-1066 SDRAM.

The Cedarview family isn’t large as yet. As earlier, they fall into two groups: D for nettops and N for netbooks. The netbook varieties have lower power consumption and, unlike their predecessors and D series counterparts, support Enhanced Intel SpeedStep.

The following table lists the key specs of serially produced Cedarview CPUs which are integrated into nettops, netbooks and mainboards selling today:

The Cedarview having basically the same microarchitecture as the Pineview, the key advantages of the new CPUs are in their increased clock rates, lower heat dissipation and in the lack of single-core models. And, of course, we shouldn’t forget about the completely new graphics core which supports resolutions up to 1920x1200 with digital video interfaces and can accelerate HD video playback. There are no other innovations. Despite the transition to 32nm tech process, the cache memory size hasn’t changed.

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