A Changing Thermal Target: Discussing Haswell

Pat Gelsinger once taught me that a single microprocessor architecture can efficiently target an order of magnitude of TDPs. It's not that you can't scale above or below that range, but at that point it becomes more efficient to use a different microarchitecture.

Let's take Sandy Bridge for example. Current desktop variants of the chip exist at 65W and 95W TDPs and later this year we will see Sandy Bridge E with a 130W TDP. If we pick 130W as the upper bound for the architecture, it should be able to efficiently scale down as low as 13W - or one order of magnitude. Looking at mobile SNB processors, it does.

Intel's ultra low voltage SNB carries a 17W TDP, while mainstream mobile SNB chips are in the 35W (dual core) to 45W (quad core) range. These TDPs all include processor graphics. With Sandy Bridge, Intel has an architecture that spans from 17W all the way up to 130W. I wouldn't be too surprised if we eventually saw some ~13W SNB parts for really low power applications in the future.

At the end of Q1 of next year Intel will introduce Ivy Bridge, its first 22nm microprocessor. I fully expect Ivy Bridge to target relatively similar TDPs as Sandy Bridge, however the initial launch will be confined to TDPs less than or equal to 95W (much like SNB was).

With Lynnfield Intel made it very clear that it's possible to get high-end desktop class performance out of a 95W part. While the 130W chips were still faster, the majority of enthusiast users would get by just fine with Lynnfield. The move to Sandy Bridge highlighted Intel's move away from 130W TDPs for high-end desktop processors and down towards 95W. As I noticed in my transition to a mobile quad-core SNB notebook as my primary workstation, I believe this generation of 130W CPUs will target a smaller portion of enthusiast users than the previous generation. The trend is definitely downward, towards lower TDPs.

Haswell is where Intel's architectures take a dramatic turn. Ivy Bridge is a derivative of the Sandy Bridge architecture, which of course was designed for that 13 - 130W range. Haswell however is a brand new architecture. It'll likely look similar to Sandy and Ivy but its target TDPs will be shifted down. In mobile, Haswell designs will be set at 10 - 20W. That's not the lower bound of the design, just the target for mobile. What does that do to the rest of the scale? Intel presented this slide at its analyst day earlier this month:

In Sandy Bridge, mobile occupied the 35 - 45W range - roughly the bottom third of the architecture's target. Around Haswell two things happen: the mobile design drops and the Atom design target moves upward.

Atom will service a new expanded range from ~800mW to 8W, leaving Haswell to address the ~10W and above market. Multiply that number by 10 and we have our upper bound of 100W - which isn't much different from the 95W we see today for high-end SNB SKUs. That being said, I do believe we'll see a lot more focus around 65W in the desktop.

Meet the Ultrabook Where Does This Leave Atom?


View All Comments

  • Shadowmaster625 - Wednesday, June 01, 2011 - link

    All the reviews I can find are talking about a lot of heat and not very impressive battery life. Specifically, the i5-2537M. I wish Anandtech would do a more comprehensive review of these ultra expensive low power parts. When you comapre a 17W part with a 35W part, is the power consumption really cut in half or are they full of it? Reply
  • tipoo - Wednesday, June 01, 2011 - link

    If both systems were under 100% load, it might be cut in half. Otherwise, absolutely not. THe 35w part might finish a task three times quicker and get to idle longer. Reply
  • High John - Sunday, June 26, 2011 - link

    Surely the goal is 'ultraportability', which I would primarily evaluate in terms of performance, weight and battery life.

    Why should it matter if an Ultrabook is more than 20mm thick?

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