Broadwell-Y: Introducing the Intel Core M Processor
The new 14nm node will be leveraged across multiple product segments, from data centers to tablets,via three separate Broadwell dies. For now Intel limited the information it shared with us to the mobile-oriented Broadwell-Y chip. We are told to expect an increasing amount of details on the other Broadwell products over the next quarter, with more to come during next month's Intel Developer Conference (IDF), but for now we'll have to remain content with details about the low-power mobile spin of this chip. Of course, improvements to the Broadwell core architecture will be reflected in the other dies, too. With that in mind, let's take a closer look at Broadwell-Y, marketed under the Intel Core M moniker.
The new Core M brand will cover all of the mobile space, and Intel told us that other brands like the Celeron and Pentium M will not be applied to the Broadwell-Y SoC. While the company did not disclose any actual model numbers or clock speeds, it stressed the new chip's capability to drive a hypothetical 7 to 10mm-thick fanless form factor with a 10.1" display, enabled by a 3 to 5W version of this processor. We were allowed to handle a working prototype in the form of a sexy 7mm-thin tablet, but were not allowed to run any software or examine specifications via the control panel. Until we have a working model to test, we'll have to take Intel's word that Broadwell-Y provides a "greater than 2x reduction in TDP with better performance than Haswell-Y".
We do have some specifics when it comes to the die and package sizes though. The Broadwell-Y chip is 82mm2, scaled down about 63% compared to Haswell-Y's 130mm2 die size. As for the board package, Broadwell-Y has a 50% smaller surface area and 30% thinner package compared to Haswell-Y. Part of this reduction is made possible by the relocation of the 3DL modules to a separate, tiny PCB that is attached to the bottom of the Broadwell-Y package. Of course, motherboards will need to have an appropriately-sized hole cut to accommodate it.
Because area scaling was better than expected on the 14nm node, Intel added 20% more transistors for increased features and performance. For instance, Haswell-Y's integrated graphics has a maximum of 20 AUs, while Broadwell-Y can use up to 24. That's 20% more compute resources, and Intel also claims a 50% increase in graphics sampler throughput. The company also mentions geometry, Z, and pixel fill performance improvements due to micro-architecture changes, though the company hasn't yet been specific about what these are. 4K display compatibility was also trumpeted, and two of them are theoretically supported, but practical power draw limits for a mobile device probably make this an unlikely scenario.
Intel's Core M: Focused on Low Power
Intel claims that the Broadwell-Y 14nm design and process optimizations account for the 2x lower power than Haswell-Y, which enables fanless functionality. The key SoC statistics include 25% lower power thanks to capacitance improvements, 20% less power thanks to lower minimum voltages combined with design optimizations, up to 15% improved transistor performance at low voltages, about a 10% reduction in power thanks to lower transistor leakage, and a smaller, denser processor. Of course, Intel hasn't disclosed the specific TDPs of the products that they've based these claims on, so we'll have to wait a bit longer for more information. We do know that the chips Intel is talking about have a 10 to 15W high burst speed for quick response, followed by a three to four watt sustained operating speed a few milliseconds later under load.
Broadwell-Y features the second-generation implementation of Intel's Full Integrated Voltage Regulator (FIVR), which can speed the transition between idle and load clock states. FIVR now features non-linear droop control, and a new dual FIVR LVR mode has been added. It turns out that FIVR is not particularly efficient at very low voltages, so it can now be bypassed when necessary to save power.
The SoC has an extensive list of optimizations that target active power reduction: design process optimization to reduce minimum operating voltage and dynamic capacitance (Cdyn), a re-architecture of DDR/IO/PLL/Graphics, optimizations for Cdyn in IA/Graphics/PH, and lower operating frequency ranges for IA/GT and Cache. There are other enhancements, too, such as dynamic display voltage resolution. Graphics can be controlled by Duty Cycling Control (DCC) to reduce usable power, or even turn it on and off as necessary. The latency needed to switch the GPU on and off is negligible, and it can be reduced to as low as 12.5% of its rated operating frequency.
Clock rates are, of course, tied to both power usage and thermal output. Three boost states are leveraged to deliver the highest possible clocks while maintaining system stability. The PL3 boost state allows the most amount of power that won't damage the system's battery, used for very short spikes as needed - the kind of time spans that are measured in milliseconds. PL2 is the standard burst limit, and PL1 represents the long-term system limit of sustainable power delivery. If necessary, duty cycle throttling can turn blocks of the processor on or off to minimize power usage and heat generation.
The power and thermal management framework is handled on a system level, by tracking multiple components to measure and change as necessary. This is controlled via Intel's Dynamic Power and Thermal Management software driver.
Intel's Platform Controller Hub (PCH) has also been re-engineered for Broadwell with an eye toward power efficiency. Idle power has been reduced by 25% compared to 2013, and active power has been dropped by 20% versus Haswell's PCH-LP. There are new power domains, and a new power reduction in firmware, hardware, and software updates which include fine-grain monitoring and reporting.
In addition to power enhancements, the PCH has been improved with an Audio DSP upgrade that includes more SRAM and higher MIPS. Advanced post-processing is available, with new wake-on-voice functionality. There are also fresh management and security features. Note that the PCH is manufactured using the 22nm node, so it hasn't shrunk.
Conclusion: Promising Statistics For Intel's Core M
We probably won't have access to test Intel's Broadwell CPU for a few months at least, but based on what we've seen, the company has lived up to the lofty expectations it has set. As we mentioned in our introduction: smaller processors, lower power usage, higher performance per watt, and similar overall performance compared to the previous generation at comparable clocks. All of those attributes are very desirable from a consumer standpoint.
But a lot of questions remain this early in the game. What kind of clock rates can we expect from Intel's 14nm node? How will the GPU scale compared to Haswell? What kind of Core M pricing can we expect, and will it be low enough to inject some life into low-cost Intel tablets? All of these questions will be answered over time, and we hope that at least some of them will be answered at IDF next month. Until then, we can certainly see a lot of potential in the upcoming Broadwell line.