A Bit More On Graphics Core Next 1.1

With the launch of Hawaii, AMD is finally opening up a bit more on what Graphics Core Next 1.1 entails. No, they still aren’t giving us an official name – most references to GCN 1.1 are noting that 290X (Hawaii) and 260X (Bonaire) are part of the same IP pool – but now that AMD is in a position where they have their new flagship out they’re at least willing to discuss the official feature set.

So what does it mean to be Graphics Core Next 1.1? As it turns out, the leaked “AMD Sea Islands Instruction Set Architecture” from February appears to be spot on. Naming issues with Sea Islands aside, everything AMD has discussed as being new architecture features in Hawaii (and therefore also in Bonaire) previously showed up in that document.

As such the bulk of the changes that come with GCN 1.1 are compute oriented, and clearly are intended to play into AMD’s plans for HSA by adding features that are especially useful for the style of heterogeneous computing AMD is shooting for.

The biggest change here is support for flat (generic) addressing support, which will be critical to enabling effective use of pointers within a heterogeneous compute context. Coupled with that is a subtle change to how the ACEs (compute queues) work, allowing GPUs to have more ACEs and more queues in each ACE, versus the hard limit of 2 we’ve seen in Southern Islands. The number of ACEs is not fixed – Hawaii has 8 while Bonaire only has 2 – but it means it can be scaled up for higher-end GPUs, console APUs, etc. Finally GCN 1.1 also introduces some new instructions, including a Masked Quad Sum of Absolute Differences (MQSAD) and some FP64 floor/ceiling/truncation vector functions.

Along with these architectural changes, there are a couple of other hardware features that at this time we feel are best lumped under the GCN 1.1 banner when talking about PC GPUs, as GCN 1.1 parts were the first parts to introduce this features and every GCN 1.1 part (at least thus) far has that feature. AMD’s TrueAudio would be a prime example of this, as both Hawaii and Bonaire have integrated TrueAudio hardware, with AMD setting clear expectations that we should also see TrueAudio on future GPUs and future APUs.

AMD’s Crossfire XDMA engine is another feature that is best lumped under the GCN 1.1 banner. We’ll get to the full details of its operation in a bit, but the important part is that it’s a hardware level change (specifically an addition to their display controller functionality) that’s once again present in Hawaii and Bonaire, although only Hawaii is making full use of it at this time.

Finally we’d also roll AMD’s power management changes into the general GCN 1.1 family, again for the basic reasons listed above. AMD’s new Serial VID interface (SIV2), necessary for the large number of power states Hawaii and Bonaire support and the fast switching between them, is something that only shows up starting with GCN 1.1. AMD has implemented power management a bit differently in each product from an end user perspective – Bonaire parts have the states but lack the fine grained throttling controls that Hawaii introduces – but the underlying hardware is identical.

With that in mind, that’s a short but essential summary of what’s new with GCN 1.1. As we noted way back when Bonaire launched as the 7790, the underlying architecture isn’t going through any massive changes, and as such the differences are of primarily of interest to programmers more than end users. But they are distinct differences that will play an important role as AMD gears up to launch HSA next year. Consequently what limited fracturing there is between GCN 1.0 and GCN 1.1 is primarily due to the ancillary features, which unlike the core architectural changes are going to be of importance to end users. The addition of XDMA, TrueAudio, and improved power management (SIV2) are all small features on their own, but they are features that make GCN 1.1 a more capable, more reliable, and more feature-filled design than GCN 1.0.

The AMD Radeon R9 290X Review Hawaii: Tahiti Refined
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  • 46andtool - Thursday, October 24, 2013 - link

    I dont know where your getting your information but your obviously nvidia biased because its all wrong. AMD is known for using poor reference coolers, once manufactures like sapphire and HIS roll out there cards in a couple weeks Im sure the noise and heat wont be a problem. and the 780ti is poised to be between a 780gtx and a titan, it will not be faster than a 290x, sorry. We already have the 780ti's specs..what Nvidia needs to focus on is dropping its insane pricing. Reply
  • SolMiester - Monday, October 28, 2013 - link

    Sorry bud, but the Ti will be much faster than Titan, otherwise there is no point, hell even the 780OC is enough to edge the Titan. Why are people going on about Titan, its a once in a blue moon product to fill a void that AMD left open with CUDA dev for prosumers...Full monty with perhaps 7ghz memory, wahey! Reply
  • Samus - Friday, October 25, 2013 - link

    What in the world makes you think the 780Ti will be faster than Titan? That's ridiculous. What's next, a statement that the 760Ti will be faster than the 770? Reply
  • TheJian - Friday, October 25, 2013 - link

    http://www.techradar.com/us/news/computing-compone...
    Another shader and more mhz.
    http://news.softpedia.com/news/NVIDIA-GeForce-GTX-...
    If the specs are true quite a few sites think it will be faster than titan.
    http://hexus.net/tech/news/graphics/61445-nvidia-g...
    Check the table. 780TI would win in gflops if leak is true. The extra 80mhz+1SMX mean it should either tie or barely beat it in nearly everything.

    Even a tie at $650 would be quite awesome at less watts/heat/noise possibly. Of course it will be beat a week later buy a fully unlocked titan ultra or more mhz, or mhz+fully unlocked. NV won't just drop titan. They will make a better one easily. It's not like NV just sat on their butts for the last 8 months. It's comic anyone thinks AMD has won. OK, for a few weeks tops (and not really even now other than price looking at 1080p and the games I mentioned previously).
    Reply
  • ShieTar - Thursday, October 24, 2013 - link

    It doesn't cost less than a GTX780, it only has a lower MSRP. The actual price for which you can buy a GTX780 is already below 549$ today, so as usual you pay the same price for the same performance with both companies.

    And testing 4K gaming is important right now, but it should be another 3-5 years before 4K performance actually impacts sales figures in any relevant way.

    And about Titan? Keep in mind that it is 8 months old, still has one SMX disabled (unlike the Quadro K6000), and still uses less power in games than the 290X. So I wouldn't be surprised to see a Titan+ come out soon, with 15 SMX and higher base clocks, and as Ryan puts it in this article "building a refined GPU against a much more mature 28nm process". That should be enough to gain 10%-15% performance in anything restricted by computing power, thus showing a much more clear lead over the 290X.

    The only games that the 290X will clearly win are those that are restricted by memory bandwidth. But nVidia have proven with the 770 that they can operate memory at 7GHz as well, so they can increase Titans bandwidth by 16% through clocks alone.

    Don't get me wrong, the 290X looks like a very nice card, with a very good price to it. I just don't think nVidia has any reason to worry, this is just competition as usual, AMD have made their move, nVidia will follow.
    Reply
  • Drumsticks - Thursday, October 24, 2013 - link

    http://www.newegg.com/Product/ProductList.aspx?Sub...

    Searched on Newegg, sorted by lowest price, lowest one was surprise! $650. I don't think Newegg is over $100 off in their pricing with competitors.
    Reply
  • 46andtool - Thursday, October 24, 2013 - link

    http://www.newegg.com/Product/Product.aspx?Item=N8...

    your clearly horrible at searching
    Reply
  • TheJian - Friday, October 25, 2013 - link

    $580 isn't $550 though right? And out of stock. I wonder how many of these they can actually make seeing how hot it is already in every review pegged 94c. Nobody was able to OC it past 1125. They're clearly pushing this thing a lot already. Reply
  • ShieTar - Friday, October 25, 2013 - link

    Well, color me surprised. I admittedly didn't check the US market, because for more than a decade now, electronics used to be sold in the Euro-Region with a price conversion assumption of 1€=1$, so everything was about 35% more expensive over here (but including 19% VAT of course).

    So for this discussion I used our German comparison engines. Both the GTX780 and the R290X are sold for the same price of just over 500€ over here, which is basically 560$+19%VAT. I figured the same price policies would apply in the US, it basically always does.

    Well, as international shipping is rarely more that 15$, it would seem like your cheapest way to get a 780 right now is to actually import it from Germany. Its always been the other way around with electronics, interesting to see it the other way around for once.
    Reply
  • 46andtool - Thursday, October 24, 2013 - link

    the price of a 780gtx is not below $649 unless you are talking about a refurbished or open box card. Reply

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