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
POST A COMMENT

396 Comments

View All Comments

  • heflys - Thursday, October 24, 2013 - link

    Slightly slower than a 780 overall? Even in Uber mode? Can you link me to these reviews if possible? Reply
  • Shark321 - Thursday, October 24, 2013 - link

    I didn't say that. It's slightly slower in Uber Mode than Titan overall in 1080p (across all sites combined). In Quiet mode it's usually slightly faster than 780, slighttly slower in the minority of the reviews. Reply
  • heflys - Thursday, October 24, 2013 - link

    I see now. Reply
  • Jumangi - Thursday, October 24, 2013 - link



    What noob would buy a 290x or a Titan and run it in 1080p? A pointless resolution for these cards.
    Reply
  • inighthawki - Thursday, October 24, 2013 - link

    What an arrogant post. There are tons of people who game on 1080p displays and buy a 290X or a Titan. Having a high framerate (i.e. consistently greater than 60fps) reduces the likelihood of stuttering while playing, while also making your system a bit more future-proof as new games come out. Not everyone cares about pixel count, some care more about quality per pixel. As you start seeing titles ship on Unreal 4, post-Crysis 3, etc, I will be laughing at you when I can still run my games at native resolution without the need to upscale or reduce quality. Reply
  • puppies - Saturday, October 26, 2013 - link

    Anyone who buys a titan to play games at 1080p is insane, seriously they need locking up. You claiming otherwise does nothing. Reply
  • Samus - Thursday, October 24, 2013 - link

    agreed. this card is for 2560x1440+ or multimonitor Reply
  • TheJian - Friday, October 25, 2013 - link

    ROFL...Only if you don't believe in MAXING your games. Which nobody can do with a single card. Many sites comment on this, and show mins, even here with lower settings they hit below 30fps in a few of their games at 2560. In multiplayer you'd get crushed by guys hitting much higher fps at 1080p in many games. Maybe you'll be right at 20nm, but certainly there are far too many games you have to jockey settings around on to make you right today. Reply
  • reddev - Thursday, October 24, 2013 - link

    Both LinusTechTips and OC3D, two reviewers I trust quite a bit, have it below the 780. Reply
  • randomhkkid - Friday, October 25, 2013 - link

    Linus tech tips over clocks all the cards it tests, since the 780 has much more headroom (on the stick cooler) the gains were larger than the 290x so at stock the 290x is faster. Reply

Log in

Don't have an account? Sign up now