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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  • TheJian - Friday, October 25, 2013 - link

    Incorrect. Part of the point of gsync is when you can do 200fps in a particular part of the game they can crank up detail and USE the power you have completely rather than making the whole game for say 60fps etc. Then when all kinds of crap is happening on screen (50 guys shooting each other etc) they can drop the graphics detail down some to keep things smooth. Gsync isn't JUST frame rate. You apparently didn't read the anandtech live blog eh? You get your cake and can eat it too (stutter free, no tearing, smooth and extra power used when you have it available). Reply
  • MADDER1 - Friday, October 25, 2013 - link

    If Gsync drops the detail to maintain fps like you said, then you're really not getting the detail you thought you set. How is that having your cake and eating it too? Reply
  • Cellar Door - Friday, October 25, 2013 - link

    How so? If Mantle gets 760gtx performance in BF4 from a 260X ..will you switch then? Reply
  • Animalosity - Sunday, October 27, 2013 - link

    No. You are sadly mistaken sir. Reply
  • Antiflash - Thursday, October 24, 2013 - link

    I've usually prefer Nvidia Cards, but they have it well deserved when decided to price GK110 to the stratosphere just "because they can" and had no competition. That's poor way to treat your customers and taking advantage of fanboys. Full implementation of Tesla and Fermi were always priced around $500. Pricing Keppler GK110 at $650+ was stupid. It's silicon after all, you should get more performance for the same price each year. Not more performance at a premium price as Nvidia tried to do this generation. AMD is not doing anything extraordinary here they are just not following nvidia price gouging practices and $550 is their GPU at historical market prices for their flagship GPU. We would not have been having this discussion if Nvidia had done the same with GK110. Reply
  • inighthawki - Thursday, October 24, 2013 - link

    " It's silicon after all, you should get more performance for the same price each year"

    So R&D costs come from where, exactly? Not sure why people always forget that there is actual R&D that goes into these types of products, it's not just some $5 just of plastic and silicon + some labor and manufacturing costs. Like when they break down phones and tablets and calculate costs they never account for this. As if their engineers are basically just selecting components on newegg and plugging them together.
    Reply
  • jecastejon - Thursday, October 24, 2013 - link

    R&D. Is R&D tied only to a specific Nvidia card? AMD as others also invest a lot in R&D with every product generation, even if they are not successful. Nvidia will have to do a reality cheek with their pricing and be loyal to their fans and the market. Today's advantages don't last for to long. Reply
  • Antiflash - Thursday, October 24, 2013 - link

    NVIDIA's logic. Kepler refresh: 30% more performance => 100% increase in price
    AMD's logic. GCN refresh: is 30% more preformance => 0% increase in price
    I can't see how this is justified by R&D of just a greedy company squishing its more loyal customer base.
    Reply
  • Antiflash - Thursday, October 24, 2013 - link

    Just for clarification. price comparison between cards at its introduction comparing NVIDIA's 680 vs Titan and AMD's 7970 vs 290x Reply
  • TheJian - Friday, October 25, 2013 - link

    AMD way=ZERO PROFITS company going broke, debt high, 6Bil losses in 10yrs
    NV way=500-800mil profits per year so you can keep your drivers working.

    Your love of AMD's pricing is dumb. They are broke. They have sold nearly everything they have or had, fabs, land, all that is left is the company itself and IP.

    AMD should have priced this card at $650 period. Also note, NV hasn't made as much money as 2007 for 6 years. They are not gouging you or they would make MORE than before in 2007 right? Intel, Apple, MS are gouging you as they all make more now than then (2007 was pretty much highs for a lot of companies, down since). People like you make me want to vomit as you just are KILLING AMD, which in turn will eventually cost me dearly buying NV cards as they will be the only ones with real power in the next few years. AMD already gave up the cpu race. How much longer you think they can fund the gpu race with no profits? 200mil owed to GF in Dec 31, so the meager profit they made last Q and any they might have made next Q is GONE. They won't make 200mil profit next Q...LOL. Thanks to people like you asking for LOW pricing and free games.

    You don't even understand you are ANTI-AMD...LOL. Your crap logic is killing them (and making NV get 300mil less profit than 2007). The war is hurting them both. I'd rather have AMD making 500mil and NV making 1B than what we get now AMD at ZERO and NV at 550mil.
    Reply

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