More Details on the Atom Z3000 Processor Architecture
While I already discussed most of what has changed in the new Silvermont architecture powering the Atom Z3000 line, a recap and shortened version of the data is necessary to continue. First, the new Atom is built on the same 22nm process used on the top end Haswell Core-series processors and brings with it some significant advantages having been tuned for efficiency. One of Intel’s strongest areas is in process technology and no other company is really on par with them in this area. By leveraging that, Intel can take designs and architectures much further than competing companies that must make compromises to fit in similar power envelopes.
The new Atom processors are quad-core, quad-thread designs with out-of-order architectures, the first in the history of Atom. HyperThreading was left out in favor of the OOO design and Intel told me that the tradeoff for OOO in die space and complexity was paid for by the removal of HT. HyperThreading has always been a good feature, but the advantages of native quad-core (compared to dual-core with HyperThreading) have been pointed out numerous times in performance testing. Intel Burst Technology allows the SoCs to clock higher on the CPU or GPU blocks when power and thermal headroom is available and allows the Atom Z3000 to address a wider range of product ranges.
Bay Trail can support either low power DDR3-1067 (in dual 64-bit channels) or DDR3L-RS at 1333 MHz (in single channel) which allows them to create the different SKU options covered previously in this article which allows for greater product flexibility and implementation options.
Perhaps nearly as important as the move to an OOO x86 design is the transition to Intel HD Graphics and video architecture, away from the PowerVR designs that Atom has used in the past. With Haswell we saw a big change in the way Intel was focusing on the GPU portion of their processors and though Bay Trail implementations are based on the Ivy Bridge version of Intel HD Graphics, the improvements should be immediately noticeable. The Atom Z3000 series will include 4 Execution Units (EUs) as well as support for dynamic frequencies (up to 667 MHz), media encode and decode acceleration and resolutions up to 2560×1600. For comparison, both Sandy Bridge and Ivy Bridge HD graphics solutions include 16 EUs, running at higher clocks.
Intel did confirm for me that there was a graphics cache on the SoC as well but left other details out. It is not a shared cache apparently (between CPU and GPU) so you aren't going to see the potential performance and heterogeneous benefits, and the size of said cache remains a mystery as well.
Also important is support for InstantGo, or what was previously known as Microsoft Connected Standby. This is the technology that allows the system to get background updates under very low power states so that your data is always refreshed and ready when you open the laptop or wake up the tablet. Without support for this the ~3 week standby claim would not be possible.
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This newer, more detailed block diagram of Bay Trail / Atom Z3000 SoCs details all of the interconnects between hardware components. The Silvermont System Agent is the device that is responsible for memory controller utilization, graphics memory access, display controllers and interfacing with the switching fabric responsible for the connectivity features.
The CPU modules each feature two processing cores and 1MB of shared L2 cache and allow those two cores to easily and efficiently share data between threads. It does mean that inter-module communications have to be made through the system agent which has been completely re-built for this architecture. Intel claims that it is very high bandwidth but wouldn’t go into exact details only telling me that it had “more than enough” to handle all the I/O it is responsible for.
Silvermont’s primary switching fabric that connects things like GPIO, storage, USB and audio to the processor uses a QoS (quality of service) protocol to maintain a balance of performance and power efficiency. Just as you might see it integrated on your home router, QoS basically means that some kind of logic is applied to data I/O requests and balanced so that higher priority requests are met leaving less important ones to halt until space is made in the cycle.
Obviously Intel has included support for nearly all the industry standard interconnects for tablets and portable devices like GPIO, I2C and even is able to embed support for USB 3.0 as well. Storage performance will be something worth testing and evaluating though as the eMMC interconnect will likely be the primary option for storage media.
Bay Trail integrates quite a bit of media capability into the SoC starting with a high-performance and power optimized HD H.264 encoder that will be utilized for movie recording more than video conversion. This encoder is implemented completely in hardware and likely shares quite a bit with the desktop QuickSync technology, though on a lower scale. Video decode acceleration is also included in hardware for H.264, VC1, VP8 and quite a more.
Intel has support for HDCP 1.4 and 2.1 for protected content which is important for the playback of premium services even though it likely aggravates some openness proponents.
Atom Z3000 can also support multiple displays though we are somewhat bandwidth limited on the resolutions. A single display can be powered at 2560×1440 60 Hz with 24-bit color though eDP 1.3 is the most power efficient option.
Bay Trail integrates Intel Display Power Saving Technology (DPST) version 6.0 that combines backlight reduction with image enhancements to lower the power required for a high quality user experience. Though a specific panel type is required Intel can provide what they call an “equivalent” image quality by adjusting input pixel statistics for bright images while keeping power to the LCD down.
The imaging sensor on Bay Trail has the ability to capture 1080p60 video with a fully programmable processor capable of 275 Mpps (millions of pixels per second). Features like video stabilization (digital), burst photo mode, low light noise reduction and more.