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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  • SolMiester - Monday, October 28, 2013 - link

    So you can OC a 780 on stock, but not the 290x to sustain the OC, which means 780 wins!, especially after the price drop to $500!, oh dear AMD 290x just went from hero to zero... Reply
  • TheJian - Friday, October 25, 2013 - link

    I gave links and named the games previously...See my post. At 1080p 780 trades blows depending on the games. Considering 98.75% of us are 1920x1200 or less, that is important and you get 3 AAA games with 780, on top of the fact that it's using far less watts, less noise and less heat. A simple drop in price of $50-100 and 780 seems like a no brainer to me (disregarding the 780TI which should keep the same price as now I'd guess). Granted Titan needs a dunk in price now too, which I'm sure will come or they'll just replace it with a full SMX up-clocked titan to keep that price. I'm guessing old titan just died as 780TI will likely beat it in nearly everything if the rumored clock speed and extra smx are true. They will have to release a new titan ULTRA or something with another smx or up the mhz to 1ghz or something. OR hopefully BOTH.

    I'm guessing it's easier to just up the 100mhz or put it to 1ghz as surely manufacturing has gotten them to where all will do this now, more than having all SMX's defect free. Then again if you have a bad SMX just turn a few more off and it's a 780TI anyway. They've had 8 months to either pile up cherry picked ones, or just improve totally anyway so more can do this easily. Clearly 780ti was just waiting in the wings already. They were just waiting to see 290x perf and estimates.
    Reply
  • eddieveenstra - Sunday, October 27, 2013 - link

    Titan died when 780gtx entered the room at 600 Euro. I'm betting Nvidia only brings a 780gtx ti and that's it. Titan goes EOL. Reply
  • anubis44 - Thursday, October 24, 2013 - link

    This is the reference card. It's not loud unless you set it to 'Uber' mode, and even then, HardOCP thought the max fan speed should be set to 100% rather than 55%. Imagine how quiet an Asus Direct CUIII or Gigabyte Windforce or Sapphire Toxic custom cooled R9 290x will be.

    Crossfire and frame pacing all working, and R9 290X crushes Titan in 4K gaming (read HardOCP's review of this 4K section), all while costing $100 less than GTX780, and the R9 280X (7970) is priced at $299, and the R9 270X (7870) is now going for $180, and now Mantle API could be the next 3dfx Glide, and boost all 7000-series cards and higher dramatically for free...

    It's like AMD just pulled out a light sabre and cut nVidia right in half while Jsen Hsun just stares dumbly at them in disbelief. He should have merged nVidia with AMD when he had the chance. Could be too late now.
    Reply
  • Shark321 - Thursday, October 24, 2013 - link

    There will be no custom cooling solution for the time being. It's the loudest card ever released. Twice as loud as 780/Titan in BF3 after 10 minutes of playing. Also Nvidia will bringt the 780Ti in 3 weeks, a faster cart at a comparable price, but quiet. AMD releases the 290x one year after NVidia, 2 years after NVidias tipeout. Nvidia will be able to counter this with a wink. Reply
  • just4U - Thursday, October 24, 2013 - link

    Shark Writes: "It's the loudest card ever released."

    Guess you weren't around for the Geforce5...
    Reply
  • HisDivineOrder - Thursday, October 24, 2013 - link

    The FX5800 is not ever dead. Not if we remember the shrill sound of its fans...

    ...or if the sound burned itself into our brains for all time.
    Reply
  • Samus - Friday, October 25, 2013 - link

    I think the 65nm GeForce 280 takes the cake for loudest card ever made. It was the first card with a blower. Reply
  • ninjaquick - Thursday, October 24, 2013 - link

    lol, the Ti can only do so much, there is no smaller node for either company to jump to, not until March for enough shipments to have stock for sales. The 290X just proves AMD's GCN design is a keeper. It is getting massively throttled by heat and still manages to pull a slight lead over the titan, at sometimes 15% lower clocks than reference. AMD needed a brand for this release season, and they have it.

    Both Nvidia and AMD are jumping to the next node in 2014. Nvidia will not release Maxwell on the current node. And there is no other node they would invest in going to.
    Reply
  • HisDivineOrder - Thursday, October 24, 2013 - link

    The Ti could theoretically open up all the disabled parts of the current GK110 part. Doing that, who knows what might happen? We've yet to see a fully enabled GK110. I suspect that might eat away some of the Titan's efficiency advantage, though. Reply

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