On-Package PCH, The First Single Chip Haswell

In 2010, with Clarkdale and Arrandale, Intel went from a 3-chip platform solution (CPU, IOH/MCH, ICH) down to a 2-chip platform (CPU + PCH). With Haswell, we see the first instantiation of a single-chip Core platform.

With the 8-series chipset, Intel moved from a 65nm process on the 7-series chipset to 32nm, skipping 45nm entirely. An older, less mobile-focused Intel would try to keep its chipsets on the oldest, economically sensible node possible, but these days things are different. The move to 32nm cuts TDP down considerably. Intel hasn’t publicly documented the power consumption any of its ultra mobile chipsets, but if we look at QM77 to QM87 we see a 34% decrease in TDP.

In Haswell desktop and standard voltage mobile parts, the 8-series chipset remains a an off-chip solution in a discrete package. With Haswell ULT and ULX (U and Y series SKUs), the 8-series PCH (Platform Controller Hub) moves on-package. Since it’s on-package, the TDP of the PCH is included in the overall TDP of the processor.

Bringing the PCH on-package not only saves space on the motherboard, but it also reduces the power needed to communicate with the chip. Signals no longer have to travel off die, through the package, via traces on the motherboard to the PCH. Instead you get much lower power on-package communication.

Intel also changed the interface between the CPU and PCH to a new on-package interface instead of DMI. Presumably Intel’s OPI is designed for much lower power operation.

Although PCIe support remains on the PCH (6 PCIe 2.0 lanes), there’s no external PCIe interface from the CPU itself. Any hopes for pairing a meaningfully high performance discrete GPU with Haswell ULT are dead. We didn’t see a ton of Ivy Bridge Ultrabooks with discrete GPUs, but the option simply won’t exist this time around. All of the sudden the creation of Intel’s 28W Haswell ULT with GT3 graphics makes a lot more sense. Haswell ULT lacks native VGA support. Update: NVIDIA tells me that it fully supports running a dGPU off of a x4 connection to the PCH. It's not the ideal solution, but discrete GPUs will still technically be possible with Haswell ULT.

Intel adds SDIO support. USB 3 and 6Gbps SATA are both there as well (although with fewer max ports supported compared to the desktop PCH, up to 4 and 3 respectively). There’s also a lot more sharing of bandwidth between individual PCIe lanes and USB/SATA. These limits shouldn’t be an issue given the port/drive configuration of most Ultrabooks.

Introduction Haswell ULT: Platform Power Improvements
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  • xTRICKYxx - Sunday, June 9, 2013 - link

    AMD's target market has been at a considerably lower price platform than Intel's Ultrabook.
  • zdw - Sunday, June 9, 2013 - link

    6 PCIe 2.0 lanes is probably the minimum possible for a MacBook Air, as ThunderBolt + WiFi would take up a 4x and 1x respectively.
  • risa2000 - Sunday, June 9, 2013 - link

    So, if I minimize task manager into tray, which updates, let's say, every second, does it mean I will wake up the GPU and save and restore the buffer into display's DRAM every second just for this update? What would be the impact on battery life?
    (If there is a tray on Win 8, as of which I am not sure right now.)
  • tential - Sunday, June 9, 2013 - link

    There is a tray.
  • A5 - Sunday, June 9, 2013 - link

    It would wake up the GPU whenever something that is on-screen changes. Once per second is still much better than 60 times per second.
  • Synaesthesia - Sunday, June 9, 2013 - link

    It can remain in sleep state for most of that second so it won't impact the battery much, particularly with Haswell.
  • mikk - Sunday, June 9, 2013 - link

    Why is there no memory configuration detail in the test? This is tremendously important especially for integrated GPU tests. Because we don't know this all gaming tests are completely useless. Bad job.
  • Homeles - Sunday, June 9, 2013 - link

    You've completely missed the point of this review.
  • mikk - Sunday, June 9, 2013 - link

    I think you did.
  • Egg - Sunday, June 9, 2013 - link

    I'm assuming they're comparable between the Acer S7s. But I could be wrong.

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