Haswell's GPU

Although Intel provided a good amount of detail on the CPU enhancements to Haswell, the graphics discussion at IDF was fairly limited. That being said, there's still some to talk about here.

Haswell builds on the same fundamental GPU architecture we saw in Ivy Bridge. We won't see a dramatic redesign/re-plumbing of the graphics hardware until Broadwell in 2014 (that one is going to be a big one).

Haswell's GPU will be available in three physical configurations: GT1, GT2 and GT3. Although Intel mentioned that the Haswell GT3 config would have twice the shader count of Haswell GT2, it was careful not to disclose the total number of EUs in any of the versions. Based on the information we have at this point, GT3 should be a 40 EU configuration while GT2 should feature 20 EUs. Intel will also be including up to one redundant EU to deal with the case where there's a defect in an EU in the array. This isn't an uncommon practice, but it does indicate just how much of the die will be dedicated to graphics in Haswell. The larger of an area the GPU covers, the greater the likelihood that you'll see unrecoverable defects in the GPU. Redundancy at the EU level is one way of mitigating that problem.

Haswell's processor graphics extends API support to DirectX 11.1, OpenCL 1.2 and OpenGL 4.0.

At the front of the graphics pipeline is a new resource streamer. The RS offloads some driver work that the CPU would normally handle and moves it to GPU hardware instead. Both AMD and NVIDIA have significant command processors so this doesn't appear to be an Intel advantage although the devil is in the (unshared) details. The point from Intel's perspective is that any amount of processing it can shift away from general purpose CPU hardware and onto the GPU can save power (CPU cores go to sleep while the RS/CS do their job).

Beyond the resource streamer, most of the fixed function graphics hardware sees a doubling of performance in Haswell.

At the shader core level, Intel separates the GPU design into two sections: slice common and sub-slice. Slice common includes the rasterizer, pixel back end and GPU L3 cache. The sub-slice includes all of the EUs, instruction caches and EUs.

In Haswell GT1 and GT2 there's a single slice common, while GT3 sees a doubling of slice common. GT3 similarly has two sub-slices, although once again Intel isn't talking specifics about EU counts or clock speeds between GT1/2/3.

The final bit of detail Intel gave out about Haswell's GPU is the texture sampler sees up to a 4x improvement in throughput over Ivy Bridge in some modes.

Now to the things that Intel didn't let loose at IDF. Although originally an option for Ivy Bridge (but higher ups at Intel killed plans for it) was a GT3 part with some form of embedded DRAM. Rumor has it that Apple was the only customer who really demanded it at the time, and Intel wasn't willing to build a SKU just for Apple.

Haswell will do what Ivy Bridge didn't. You'll see a version of Haswell with up to 128MB of embedded DRAM, with a lot of bandwidth available between it and the core. Both the CPU and GPU will be able to access this embedded DRAM, although there are obvious implications for graphics.

Overall performance gains should be about 2x for GT3 (presumably with eDRAM) over HD 4000 in a high TDP part. In Ultrabooks those gains will be limited to around 30% max given the strict power limits.

As for why Intel isn't talking about embedded DRAM on Haswell, your guess is as good as mine. The likely release timeframe for Haswell is close to June 2013, there's still tons of time between now and then. It looks like Intel still has a desire to remain quiet on some fronts.

TSX Haswell Media Engine: QuickSync the Third
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  • Rectified - Friday, October 05, 2012 - link

    Anand, you write the best tech articles on the web. As a graduate student in computer engineering, I appreciate the practical yet technical analyses you write on the industry. Keep it up! Reply
  • Crazy1 - Friday, October 05, 2012 - link

    I like the concept of Panel Self Refresh, yet I feel that Intel could implement this themselves. I'm not an expert, but couldn't a buffer be placed on the CPU package between the GPU and panel? This may not be as efficient as if the panel makers did it themselves and it would probably only work when using the IGP (when it would most likely have the greatest impact), but at least it is a step in the right direction.

    Additionally, Great Article! Anandtech provides some of the most thorough technology articles. Keep it up.
    Reply
  • random2 - Saturday, October 06, 2012 - link

    " If all mainstream client computing moves to smartphones,..........."

    Seriously? The idea of all mainstream computing done on nothing but smartphones seems to stretch the imagination just a bit much. There isn't even the most basic of businesses that do not have a computer (made with mainstream components as are most small and medium sized businesses) and business software. Don't forget the PC gamers and people who like larger viewing and typing surfaces. Or the fact that in eight years, home and business PC's will be blindingly fast with larger displays with much greater pixel density, possibly clear screen touch surfaces, likely alternative interfaces than just a keyboard and mouse and incredible computing and rendering power.

    The likelihood of the general populace turning all their computing needs over to a palm size PC I see as kind of weird fantasy where people learn to love minute typing interfaces and squinting at hi density displays fit into 3.5by 4.5 inches for long periods of the day without interruption. No, to push the idea of micro computing one must discount all of the other advances in the computer/electronics industries in order to make their pet theory viable.
    Reply
  • random2 - Saturday, October 06, 2012 - link

    "The race to the bottom that we've seen in the LCD space made it unlikely that any of the panel vendors would be jumping at the opportunity to make their products more expensive."

    It's unfortunate, because of what might have been had the manufacturers, of which there are only three main ones, if I recall, had the foresight to market to customers that weren't just looking to buy the lowest priced panel on display at Best Buy. Had they the initiative to have started years ago, there would be some pretty fantastic panels available today for much more reasonable prices than seen for the 27 and 30 inch 2560X1600 panels today.
    Reply
  • Klugfan - Saturday, October 06, 2012 - link

    This doesn't really belong in the Haswell article, but I would love to know more about the physics and constraints of TDP. Like, hit me with a chart of TDP impact for a variety of important parts in phones, tablets, laptops, and desktops. Show me a chart of TDP budgets and mitigation strategies. Explain to me roughly how physics forces those things to relate. Please.

    Seems important and it's easy to understand the comparison from Ivy Bridge to Haswell but that doesn't feel like the big picture.
    Reply
  • havoti97 - Saturday, October 06, 2012 - link

    I read the 1st page then got bored. Writing style is overly wordy... am I the only the feeling this way? Reply
  • xeizo - Saturday, October 06, 2012 - link

    It's an article, not a twitter feed! Some of us like to get the whole picture not just the flashy stuff .... Reply
  • watersb - Saturday, October 06, 2012 - link

    Phenomenal feature, Anand! This is why I check your site each day. Thanks very much! Reply
  • bill4 - Saturday, October 06, 2012 - link

    like atom, you're stuck in no mans land. way too high for tablets and phones, but in desktops and laptop, who cares if the amd solution uses 30 watts instead of 8? that difference isn't enough to matter when you take the whole platform into account, especially at lower price points where battery life wont be fantastic anyway. on the dsktop it's completely pointless. Reply
  • JlHADJOE - Sunday, October 07, 2012 - link

    On a laptop using 30 watts instead of 8 will more than triple your battery life, especially at lower price points/smaller form factors where manufacturers gimp the battery.

    How's about browsing for 9 hours instead of 3? Or 27 hours instead of 9? I'd jump on it in a heartbeat.
    Reply

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