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Digging into a specific market
A little while ago, I decided to think about processor design as a game. You are given a budget of complexity, which is determined by your process node, power, heat, die size, and so forth, and the objective is to lay out features in the way that suits your goal and workload best. While not the topic of today's post, GPUs are a great example of what I mean. They make the assumption that in a batch of work, nearby tasks are very similar, such as the math behind two neighboring pixels on the screen. This assumption allows GPU manufacturers to save complexity by chaining dozens of cores together into not-quite-independent work groups. The circuit fits the work better, and thus it lets more get done in the same complexity budget.
Carrizo is aiming at a 63 million unit per year market segment.
This article is about Carrizo, though. This is AMD's sixth-generation APU, starting with Llano's release in June 2011. For this launch, Carrizo is targeting the 15W and 35W power envelopes for $400-$700 USD notebook devices. AMD needed to increase efficiency on the same, 28nm process that we have seen in their product stack since Kabini and Temash were released in May of 2013. They tasked their engineers to optimize their APU's design for these constraints, which led to dense architectures and clever features on the same budget of complexity, rather than smaller transistors or a bigger die.
15W was their primary target, and they claim to have exceeded their own expectations.
Backing up for a second. Beep. Beep. Beep. Beep.
When I met with AMD last month, I brought up the Bulldozer architecture with many individuals. I suspected that it was a quite clever design that didn't reach its potential because of external factors. As I started this editorial, processor design is a game and, if you can save complexity by knowing your workload, you can do more with less.
Bulldozer looked like it wanted to take a shortcut by cutting elements that its designers believed would be redundant going forward. First and foremost, two cores share a single floating point (decimal) unit. While you need some floating point capacity, upcoming workloads could use the GPU for a massive increase in performance, which is right there on the same die. As such, the complexity that is dedicated to every second FPU can be cut and used for something else. You can see this trend throughout various elements of the architecture.
When NVIDIA launched the GeForce GTX Titan X card only back in March of this year, I knew immediately that the GTX 980 Ti would be close behind. The Titan X was so different from the GTX 980 when it came to pricing and memory capacity (12GB, really??) that NVIDIA had set up the perfect gap with which to place the newly minted GTX 980 Ti. Today we get to take the wraps off of that new graphics card and I think you'll be impressed with what you find, especially when you compare its value to the Titan X.
Based on the same Maxwell architecture and GM200 GPU, with some minor changes to GPU core count, memory size and boost speeds, the GTX 980 Ti finds itself in a unique spot in the GeForce lineup. Performance-wise it's basically identical in real-world game testing to the GTX Titan X, yet is priced $350 less that that 12GB behemoth. Couple that with a modest $50 price drop in the GTX 980 cards and you have all markers of an enthusiast graphics card that will sell as well as any we have seen in recent generations.
The devil is in all the other details, of course. AMD has its own plans for this summer but the Radeon R9 290X is still sitting there at a measly $320, undercutting the GTX 980 Ti by more than half. NVIDIA seems to be pricing its own GPUs as if it isn't even concerned with what AMD and the Radeon brand are doing. That could be dangerous if it goes on too long, but for today, can the R9 290X put up enough fight with the aging Hawaii XT GPU to make its value case to gamers on the fence?
Will the GeForce GTX 980 Ti be the next high-end GPU to make a splash in the market, or will it make a thud at the bottom of the GPU gene pool? Let's dive into it, shall we?
Big Things, Small Packages
Sapphire isn’t a brand we have covered in a while, so it is nice to see a new and interesting product drop on our door. Sapphire was a relative unknown until around the release of the Radeon 9700 Pro days. This was around the time when ATI decided that they did not want to be so vertically integrated, so allowed other companies to start buying their chips and making their own cards. This was done to provide a bit of stability for ATI pricing, as they didn’t have to worry about a volatile component market that could cause their margins to plummet. By selling just the chips to partners, ATI could more adequately control margins on their own product while allowing their partners to make their own deals and component choices for the finished card.
ATI had very limited graphics card production of their own, so they often would farm out production to second sources. One of these sources ended up turning into Sapphire. When ATI finally allowed other partners to produce and brand their own ATI based products, Sapphire already had a leg up on the competition by being a large producer already of ATI products. They soon controlled a good portion of the marketplace by their contacts, pricing, and close relationship with ATI.
Since this time ATI has been bought up by AMD and they no longer produce any ATI branded cards. Going vertical when it come to producing their own chips and video cards was obviously a bad idea, we can look back at 3dfx and their attempt at vertical integration and how that ended for the company. AMD obviously produces an initial reference version of their cards and coolers, but allows their partners to sell the “sticker” version and then develop their own designs. This has worked very well for both NVIDIA and AMD, and it has allowed their partners to further differentiate their product from the competition.
Sapphire usually does a bang up job on packaging the graphics card. Oh look, a mousepad!
Sapphire is not as big of a player as they used to be, but they are still one of the primary partners of AMD. It would not surprise me in the least if they still produced the reference designs for AMD and then distributed those products to other partners. Sapphire is known for building a very good quality card and their cooling solutions have been well received as well. The company does have some stiff competition from the likes of Asus, MSI, and others for this particular market. Unlike those two particular companies, Sapphire obviously does not make any NVIDIA based boards. This has been a blessing and a curse, depending on what the cycle is looking like between AMD and NVIDIA and who has dominance in any particular marketplace.
High Bandwidth Memory
UPDATE: I have embedded an excerpt from our PC Perspective Podcast that discusses the HBM technology that you might want to check out in addition to the story below.
The chances are good that if you have been reading PC Perspective or almost any other website that focuses on GPU technologies for the past year, you have read the acronym HBM. You might have even seen its full name: high bandwidth memory. HBM is a new technology that aims to turn the ability for a processor (GPU, CPU, APU, etc.) to access memory upside down, almost literally. AMD has already publicly stated that its next generation flagship Radeon GPU will use HBM as part of its design, but it wasn’t until today that we could talk about what HBM actually offers to a high performance processor like Fiji. At its core HBM drastically changes how the memory interface works, how much power is required for it and what metrics we will use to compare competing memory architectures. AMD and its partners started working on HBM with the industry more than 7 years ago, and with the first retail product nearly ready to ship, it’s time to learn about HBM.
We got some time with AMD’s Joe Macri, Corporate Vice President and Product CTO, to talk about AMD’s move to HBM and how it will shift the direction of AMD products going forward.
The first step in understanding HBM is to understand why it’s needed in the first place. Current GPUs, including the AMD Radeon R9 290X and the NVIDIA GeForce GTX 980, utilize a memory technology known as GDDR5. This architecture has scaled well over the past several GPU generations but we are starting to enter the world of diminishing returns. Balancing memory performance and power consumption is always a tough battle; just ask ARM about it. On the desktop component side we have much larger power envelopes to work inside but the power curve that GDDR5 is on will soon hit a wall, if you plot it far enough into the future. The result will be either drastically higher power consuming graphics cards or stalling performance improvements of the graphics market – something we have not really seen in its history.
While it’s clearly possible that current and maybe even next generation GPU designs could still have depended on GDDR5 as the memory interface, the move to a different solution is needed for the future; AMD is just making the jump earlier than the rest of the industry.
DirectX 12 Has No More Secrets
The DirectX 12 API is finalized and the last of its features are known. Before the BUILD conference, the list consisted of Conservative Rasterization, Rasterizer Ordered Viewed, Typed UAV Load, Volume Tiled Resources, and a new Tiled Resources revision for non-volumetric content. When the GeForce GTX 980 launched, NVIDIA claimed it would be compatible with DirectX 12 features. Enthusiasts were skeptical, because Microsoft did not officially finalize the spec at the time.
Last week, Microsoft announced the last feature of the graphics API: Multiadapter.
We already knew that Multiadapter existed, at least to some extent. It is the part of the specification that allows developers to address multiple graphics adapters to split tasks between them. In DirectX 11 and earlier, secondary GPUs would remain idle unless the graphics driver sprinkled some magic fair dust on it with SLI, CrossFire, or Hybrid CrossFire. The only other way to access this dormant hardware was by spinning up an OpenCL (or similar compute API) context on the side.
Way back in January of this year, while attending CES 2015 in Las Vegas, we wandered into the MSI suite without having any idea what we might see as new and exciting product. Besides the GT80 notebook with a mechanical keyboard on it, the MSI GS30 Shadow was easily the most interesting and exciting technology. Although MSI is not the first company to try this, the Shadow is the most recent attempt to combine the benefits of a thin and light notebook with a discrete, high performance GPU when the former is connected to the latter's docking station.
The idea has always been simple but the implementation has always been complex. Take a thin, light, moderately powered notebook that is usable and high quality in its own right and combine it with the ability to connect a discrete GPU while at home for gaming purposes. In theory, this is the best of both worlds: a notebook PC for mobile productivity and gaming capability courtesy of an external GPU. But as the years have gone on, more companies try and more companies fail; the integration process is just never as perfect a mix as we hope.
Today we see if MSI and the GS30 Shadow can fare any better. Does the combination of a very high performance thin and light notebook and the GamingDock truly create a mobile and gaming system that is worth your investment?
It's more than just a branding issue
As a part of my look at the first wave of AMD FreeSync monitors hitting the market, I wrote an analysis of how the competing technologies of FreeSync and G-Sync differ from one another. It was a complex topic that I tried to state in as succinct a fashion as possible given the time constraints and that the article subject was on FreeSync specifically. I'm going to include a portion of that discussion here, to recap:
First, we need to look inside the VRR window, the zone in which the monitor and AMD claims that variable refresh should be working without tears and without stutter. On the LG 34UM67 for example, that range is 48-75 Hz, so frame rates between 48 FPS and 75 FPS should be smooth. Next we want to look above the window, or at frame rates above the 75 Hz maximum refresh rate of the window. Finally, and maybe most importantly, we need to look below the window, at frame rates under the minimum rated variable refresh target, in this example it would be 48 FPS.
AMD FreeSync offers more flexibility for the gamer than G-Sync around this VRR window. For both above and below the variable refresh area, AMD allows gamers to continue to select a VSync enabled or disabled setting. That setting will be handled as you are used to it today when your game frame rate extends outside the VRR window. So, for our 34UM67 monitor example, if your game is capable of rendering at a frame rate of 85 FPS then you will either see tearing on your screen (if you have VSync disabled) or you will get a static frame rate of 75 FPS, matching the top refresh rate of the panel itself. If your game is rendering at 40 FPS, lower than the minimum VRR window, then you will again see the result of tearing (with VSync off) or the potential for stutter and hitching (with VSync on).
But what happens with this FreeSync monitor and theoretical G-Sync monitor below the window? AMD’s implementation means that you get the option of disabling or enabling VSync. For the 34UM67 as soon as your game frame rate drops under 48 FPS you will either see tearing on your screen or you will begin to see hints of stutter and judder as the typical (and previously mentioned) VSync concerns again crop their head up. At lower frame rates (below the window) these artifacts will actually impact your gaming experience much more dramatically than at higher frame rates (above the window).
G-Sync treats this “below the window” scenario very differently. Rather than reverting to VSync on or off, the module in the G-Sync display is responsible for auto-refreshing the screen if the frame rate dips below the minimum refresh of the panel that would otherwise be affected by flicker. So, in a 30-144 Hz G-Sync monitor, we have measured that when the frame rate actually gets to 29 FPS, the display is actually refreshing at 58 Hz, each frame being “drawn” one extra instance to avoid flicker of the pixels but still maintains a tear free and stutter free animation. If the frame rate dips to 25 FPS, then the screen draws at 50 Hz. If the frame rate drops to something more extreme like 14 FPS, we actually see the module quadruple drawing the frame, taking the refresh rate back to 56 Hz. It’s a clever trick that keeps the VRR goals and prevents a degradation of the gaming experience. But, this method requires a local frame buffer and requires logic on the display controller to work. Hence, the current implementation in a G-Sync module.
As you can see, the topic is complicated. So Allyn and I (and an aging analog oscilloscope) decided to take it upon ourselves to try and understand and teach the implementation differences with the help of some science. The video below is where the heart of this story is focused, though I have some visual aids embedded after it.
Still not clear on what this means for frame rates and refresh rates on current FreeSync and G-Sync monitors? Maybe this will help.
Our first DX12 Performance Results
Late last week, Microsoft approached me to see if I would be interested in working with them and with Futuremark on the release of the new 3DMark API Overhead Feature Test. Of course I jumped at the chance, with DirectX 12 being one of the hottest discussion topics among gamers, PC enthusiasts and developers in recent history. Microsoft set us up with the latest iteration of 3DMark and the latest DX12-ready drivers from AMD, NVIDIA and Intel. From there, off we went.
First we need to discuss exactly what the 3DMark API Overhead Feature Test is (and also what it is not). The feature test will be a part of the next revision of 3DMark, which will likely ship in time with the full Windows 10 release. Futuremark claims that it is the "world's first independent" test that allows you to compare the performance of three different APIs: DX12, DX11 and even Mantle.
It was almost one year ago that Microsoft officially unveiled the plans for DirectX 12: a move to a more efficient API that can better utilize the CPU and platform capabilities of future, and most importantly current, systems. Josh wrote up a solid editorial on what we believe DX12 means for the future of gaming, and in particular for PC gaming, that you should check out if you want more background on the direction DX12 has set.
One of DX12 keys for becoming more efficient is the ability for developers to get closer to the metal, which is a phrase to indicate that game and engine coders can access more power of the system (CPU and GPU) without having to have its hand held by the API itself. The most direct benefit of this, as we saw with AMD's Mantle implementation over the past couple of years, is improved quantity of draw calls that a given hardware system can utilize in a game engine.
With the release of the GeForce GTX 980 back in September of 2014, NVIDIA took the lead in performance with single GPU graphics cards. The GTX 980 and GTX 970 were both impressive options. The GTX 970 offered better performance than the R9 290 as did the GTX 980 compared to the R9 290X; on top of that, both did so while running at lower power consumption and while including new features like DX12 feature level support, HDMI 2.0 and MFAA (multi-frame antialiasing). Because of those factors, the GTX 980 and GTX 970 were fantastic sellers, helping to push NVIDIA’s market share over 75% as of the 4th quarter of 2014.
But in the back of our mind, and in the minds of many NVIDIA fans, we knew that the company had another GPU it was holding on to: the bigger, badder version of Maxwell. The only question was going to be WHEN the company would release it and sell us a new flagship GeForce card. In most instances, this decision is based on the competitive landscape, such as when AMD might be finally updating its Radeon R9 290X Hawaii family of products with the rumored R9 390X. Perhaps NVIDIA is tired of waiting or maybe the strategy is to launch soon before Fiji GPUs make their debut. Either way, NVIDIA officially took the wraps off of the new GeForce GTX TITAN X at the Game Developers Conference two weeks ago.
At the session hosted by Epic Games’ Tim Sweeney, NVIDIA CEO Jen-Hsun Huang arrived when Tim lamented about needing more GPU horsepower for their UE4 content. In his hands he had the first TITAN X GPU and talked about only a couple of specifications: the card would have 12GB of memory and it would be based on a GPU with 8 billion transistors.
Since that day, you have likely seen picture after picture, rumor after rumor, about specifications, pricing and performance. Wait no longer: the GeForce GTX TITAN X is here. With a $999 price tag and a GPU with 3072 CUDA cores, we clearly have a new king of the court.
Finally, a SHIELD Console
NVIDIA is filling out the family of the SHIELD brand today with the announcement of SHIELD, a set-top box powered by the Tegra X1 processor. SHIELD will run Android TV and act as a game playing, multimedia watching, GRID streaming device. Selling for $199 and available in May of this year, there is a lot to discuss.
Odd naming scheme aside, the SHIELD looks to be an impressive little device, sitting on your home theater or desk and bringing a ton of connectivity and performance to your TV. Running Android TV means the SHIELD will have access to the entire library of Google Play media including music, movies and apps. SHIELD supports 4K video playback at 60 Hz thanks to an HDMI 2.0 connection and fully supports H.265/HEVC decode thanks to Tegra X1 processor.
Here is a full breakdown of the device's specifications.
|NVIDIA SHIELD Specifications|
|Processor||NVIDIA® Tegra® X1 processor with 256-core Maxwell™ GPU with 3GB RAM|
|Video Features||4K Ultra-HD Ready with 4K playback and capture up to 60 fps (VP9, H265, H264)|
|Audio||7.1 and 5.1 surround sound pass through over HDMI
High-resolution audio playback up to 24-bit/192kHz over HDMI and USB
High-resolution audio upsample to 24-bit/192hHz over USB
|Wireless||802.11ac 2x2 MIMO 2.4 GHz and 5 GHz Wi-Fi
Two USB 3.0 (Type A)
MicroSD slot (supports 128GB cards)
IR Receiver (compatible with Logitech Harmony)
|Gaming Features||NVIDIA GRID™ streaming service
|SW Updates||SHIELD software upgrades directly from NVIDIA|
|Power||40W power adapter|
|Weight and Size||Weight: 23oz / 654g
Height: 5.1in / 130mm
Width: 8.3in / 210mm
Depth: 1.0in / 25mm
|OS||Android TV™, Google Cast™ Ready|
|In the box||NVIDIA SHIELD
NVIDIA SHIELD controller
HDMI cable (High Speed), USB cable (Micro-USB to USB)
Power adapter (Includes plugs for North America, Europe, UK)
|Requirements||TV with HDMI input, Internet access|
|Options||SHIELD controller, SHIELD remove, SHIELD stand|
Obviously the most important feature is the Tegra X1 SoC, built on an 8-core 64-bit ARM processor and a 256 CUDA Core Maxwell architecture GPU. This gives the SHIELD set-top more performance than basically any other mobile part on the market, and demos showing Doom 3 and Crysis 3 running natively on the hardware drive the point home. With integrated HEVC decode support the console is the first Android TV device to offer the support for 4K video content at 60 FPS.
Even though storage is only coming in at 16GB, the inclusion of an MicroSD card slot enabled expansion to as much as 128GB more for content and local games.
The first choice for networking will be the Gigabit Ethernet port, but the 2x2 dual-band 802.11ac wireless controller means that even those of us that don't have hardwired Internet going to our TV will be able to utilize all the performance and features of SHIELD.
As GDC progresses here in San Francisco, AMD took the wraps off of a new SDK for game developers to use to improve experiences with virtual reality (VR) headsets. Called LiquidVR, the goal is provide a smooth and stutter free VR experience that is universal across all headset hardware and to keep the wearer, be it a gamer or professional user, immersed.
AMD's CTO of Graphics, Raja Koduri spoke with us about the three primary tenets of the LiquidVR initiative. The 'three Cs' as it is being called are Comfort, Compatibility and Compelling Content. Ignoring the fact that we have four C's in that phrase, the premise is straight forward. Comfortable use of VR means there is little to no issues with neusea and that can be fixed with ultra-low latency between motion (of your head) and photons (hitting your eyes). For compatibility, AMD would like to assure that all VR headsets are treated equally and all provide the best experience. Oculus, HTC and others should operate in a simple, plug-and-play style. Finally, the content story is easy to grasp with a focus on solid games and software to utilize VR but AMD also wants to ensure that the rendering is scalable across different hardware and multiple GPUs.
To address these tenets AMD has built four technologies into LiquidVR: late data latching, asynchronous shaders, affinity multi-GPU, and direct-to-display.
The idea behind late data latching is to get the absolute most recent raw data from the VR engine to the users eyes. This means that rather than asking for the head position of a gamer at the beginning of a render job, LiquidVR will allow the game to ask for it at the end of the rendering pipeline, which might seem counter-intuitive. Late latch means the users head movement is tracked until the end of the frame render rather until just the beginning, saving potentially 5-10ms of delay.
Who Should Care? Thankfully, Many People
The Khronos Group has made three announcements today: Vulkan (their competitor to DirectX 12), OpenCL 2.1, and SPIR-V. Because there is actually significant overlap, we will discuss them in a single post rather than splitting them up. Each has a role in the overall goal to access and utilize graphics and compute devices.
Before we get into what everything is and does, let's give you a little tease to keep you reading. First, Khronos designs their technologies to be self-reliant. As such, while there will be some minimum hardware requirements, the OS pretty much just needs to have a driver model. Vulkan will not be limited to Windows 10 and similar operating systems. If a graphics vendor wants to go through the trouble, which is a gigantic if, Vulkan can be shimmed into Windows 8.x, Windows 7, possibly Windows Vista despite its quirks, and maybe even Windows XP. The words “and beyond” came up after Windows XP, but don't hold your breath for Windows ME or anything. Again, the further back in Windows versions you get, the larger the “if” becomes but at least the API will not have any “artificial limitations”.
Outside of Windows, the Khronos Group is the dominant API curator. Expect Vulkan on Linux, Mac, mobile operating systems, embedded operating systems, and probably a few toasters somewhere.
On that topic: there will not be a “Vulkan ES”. Vulkan is Vulkan, and it will run on desktop, mobile, VR, consoles that are open enough, and even cars and robotics. From a hardware side, the API requires a minimum of OpenGL ES 3.1 support. This is fairly high-end for mobile GPUs, but it is the first mobile spec to require compute shaders, which are an essential component of Vulkan. The presenter did not state a minimum hardware requirement for desktop GPUs, but he treated it like a non-issue. Graphics vendors will need to be the ones making the announcements in the end, though.
Quiet, Efficient Gaming
The last few weeks have been dominated by talk about the memory controller of the Maxwell based GTX 970. There are some very strong opinions about that particular issue, and certainly NVIDIA was remiss on actually informing consumers about how it handles the memory functionality of that particular product. While that debate rages, we have somewhat lost track of other products in the Maxwell range. The GTX 960 was released during this particular firestorm and, while it also shared the outstanding power/performance qualities of the Maxwell architecture, it is considered a little overpriced when compared to other cards in its price class in terms of performance.
It is easy to forget that the original Maxwell based product to hit shelves was the GTX 750 series of cards. They were released a year ago to some very interesting reviews. The board is one of the first mainstream cards in recent memory to have a power draw that is under 75 watts, but can still play games with good quality settings at 1080P resolutions. Ryan covered this very well and it turned out to be a perfect gaming card for many pre-built systems that do not have extra power connectors (or a power supply that can support 125+ watt graphics cards). These are relatively inexpensive cards and very easy to install, producing a big jump in performance as compared to the integrated graphics components of modern CPUs and APUs.
The GTX 750 and GTX 750 Ti have proven to be popular cards due to their overall price, performance, and extremely low power consumption. They also tend to produce a relatively low amount of heat, due to solid cooling combined with that low power consumption. The Maxwell architecture has also introduced some new features, but the major changes are to the overall design of the architecture as compared to Kepler. Instead of 192 cores per SMK, there are now 128 cores per SMM. NVIDIA has done a lot of work to improve performance per core as well as lower power in a fairly dramatic way. An interesting side effect is that the CPU hit with Maxwell is a couple of percentage points higher than Kepler. NVIDIA does lean a bit more on the CPU to improve overall GPU power, but most of this performance hit is covered up by some really good realtime compiler work in the driver.
Asus has taken the GTX 750 Ti and applied their STRIX design and branding to it. While there are certainly faster GPUs on the market, there are none that exhibit the power characteristics of the GTX 750 Ti. The combination of this GPU and the STRIX design should result in an extremely efficient, cool, and silent card.
A baker's dozen of GTX 960
Back on the launch day of the GeForce GTX 960, we hosted NVIDIA's Tom Petersen for a live stream. During the event, NVIDIA and its partners provided ten GTX 960 cards for our live viewers to win which we handed out through about an hour and a half. An interesting idea was proposed during the event - what would happen if we tried to overclock all of the product NVIDIA had brought along to see what the distribution of results looked like? After notifying all the winners of their prizes and asking for permission from each, we started the arduous process of testing and overclocking a total of 13 (10 prizes plus our 3 retail units already in the office) different GTX 960 cards.
Hopefully we will be able to provide a solid base of knowledge for buyers of the GTX 960 that we don't normally have the opportunity to offer: what is the range of overclocking you can expect and what is the average or median result. I think you will find the data interesting.
The 13 Contenders
Our collection of thirteen GTX 960 cards includes a handful from ASUS, EVGA and MSI. The ASUS models are all STRIX models, the EVGA cards are of the SSC variety, and the MSI cards include a single Gaming model and three 100ME. (The only difference between the Gaming and 100ME MSI cards is the color of the cooler.)
To be fair to the prize winners, I actually assigned each of them a specific graphics card before opening them up and testing them. I didn't want to be accused of favoritism by giving the best overclockers to the best readers!
Battlefield 4 Results
At the end of my first Frame Rating evaluation of the GTX 970 after the discovery of the memory architecture issue, I proposed the idea that SLI testing would need to be done to come to a more concrete conclusion on the entire debate. It seems that our readers and the community at large agreed with us in this instance, repeatedly asking for those results in the comments of the story. After spending the better part of a full day running and re-running SLI results on a pair of GeForce GTX 970 and GTX 980 cards, we have the answers you're looking for.
Today's story is going to be short on details and long on data, so if you want the full back story on what is going on why we are taking a specific look at the GTX 970 in this capacity, read here:
- Part 1: NVIDIA issues initial statement
- Part 2: Full GTX 970 memory architecture disclosed
- Part 3: Frame Rating: GTX 970 vs GTX 980
- Part 4: Frame Rating: GTX 970 SLI vs GTX 980 SLI (what you are reading now)
Okay, are we good now? Let's dive into the first set of results in Battlefield 4.
Battlefield 4 Results
Just as I did with the first GTX 970 performance testing article, I tested Battlefield 4 at 3840x2160 (4K) and utilized the game's ability to linearly scale resolution to help me increase GPU memory allocation. In the game settings you can change that scaling option by a percentage: I went from 110% to 150% in 10% increments, increasing the load on the GPU with each step.
Memory allocation between the two SLI configurations was similar, but not as perfectly aligned with each other as we saw with our single GPU testing.
In a couple of cases, at 120% and 130% scaling, the GTX 970 cards in SLI are actually each using more memory than the GTX 980 cards. That difference is only ~100MB but that delta was not present at all in the single GPU testing.
It has been an abnormal week for us here at PC Perspective. Our typical review schedule has pretty much flown out the window, and the past seven days have been filled with learning, researching, retesting, and publishing. That might sound like the norm, but in these cases the process was initiated by tips from our readers. Last Saturday (24 Jan), a few things were brewing:
- Ryan was informed by NVIDIA that the memory layout of the GTX 970 was different than expected.
- The huge (now 168 page) overclock.net forum thread about the Samsung 840 EVO slowdown was once again gaining traction.
- Someone got G-Sync working on a laptop integrated display.
We had to do a bit of triage here of course, as we can only research and write so quickly. Ryan worked the GTX 970 piece as it was the hottest item. I began a few days of research and testing on the 840 EVO slow down issue reappearing on some drives, and we kept tabs on that third thing, which at the time seemed really farfetched. With those two first items taken care of, Ryan shifted his efforts to GTX 970 SLI testing while I shifted my focus to finding out of there was any credence to this G-Sync laptop thing.
A few weeks ago, an ASUS Nordic Support rep inadvertently leaked an interim build of the NVIDIA driver. This was a mobile driver build (version 346.87) focused at their G751 line of laptops. One recipient of this driver link posted it to the ROG forum back on the 20th. A fellow by the name Gamenab, owning the same laptop cited in that thread, presumably stumbled across this driver, tried it out, and was more than likely greeted by this popup after the installation completed:
Now I know what you’re thinking, and it’s probably the same thing anyone would think. How on earth is this possible? To cut a long story short, while the link to the 346.87 driver was removed shortly after being posted to that forum, we managed to get our hands on a copy of it, installed it on the ASUS G751 that we had in for review, and wouldn’t you know it we were greeted by the same popup!
Ok, so it’s a popup, could it be a bug? We checked NVIDIA control panel and the options were consistent with that of a G-Sync connected system. We fired up the pendulum demo and watched the screen carefully, passing the machine around the office to be inspected by all. We then fired up some graphics benchmarks that were well suited to show off the technology (Unigine Heaven, Metro: Last Light, etc), and everything looked great – smooth steady pans with no juddering or tearing to be seen. Ken Addison, our Video Editor and jack of all trades, researched the panel type and found that it was likely capable of 100 Hz refresh. We quickly dug created a custom profile, hit apply, and our 75 Hz G-Sync laptop was instantly transformed into a 100 Hz G-Sync laptop!
Ryan's Note: I think it is important here to point out that we didn't just look at demos and benchmarks for this evaluation but actually looked at real-world gameplay situations. Playing through Metro: Last Light showed very smooth pans and rotation, Assassin's Creed played smoothly as well and flying through Unigine Heaven manually was a great experience. Crysis 3, Battlefield 4, etc. This was NOT just a couple of demos that we ran through - the variable refresh portion of this mobile G-Sync enabled panel was working and working very well.
At this point in our tinkering, we had no idea how or why this was working, but there was no doubt that we were getting a similar experience as we have seen with G-Sync panels. As I digested what was going on, I thought surely this can’t be as good as it seems to be… Let’s find out, shall we?
A Summary Thus Far
UPDATE 2/2/15: We have another story up that compares the GTX 980 and GTX 970 in SLI as well.
It has certainly been an interesting week for NVIDIA. It started with the release of the new GeForce GTX 960, a $199 graphics card that brought the latest iteration of Maxwell's architecture to a lower price point, competing with the Radeon R9 280 and R9 285 products. But then the proverbial stuff hit the fan with a memory issue on the GeForce GTX 970, the best selling graphics card of the second half of 2014. NVIDIA responded to the online community on Saturday morning but that was quickly followed up with a more detailed expose on the GTX 970 memory hierarchy, which included a couple of important revisions to the specifications of the GTX 970 as well.
At the heart of all this technical debate is a performance question: does the GTX 970 suffer from lower performance because of of the 3.5GB/0.5GB memory partitioning configuration? Many forum members and PC enthusiasts have been debating this for weeks with many coming away with an emphatic yes.
The newly discovered memory system of the GeForce GTX 970
Yesterday I spent the majority of my day trying to figure out a way to validate or invalidate these types of performance claims. As it turns out, finding specific game scenarios that will consistently hit targeted memory usage levels isn't as easy as it might first sound and simple things like the order of start up can vary that as well (and settings change orders). Using Battlefield 4 and Call of Duty: Advanced Warfare though, I think I have presented a couple of examples that demonstrate the issue at hand.
Performance testing is a complicated story. Lots of users have attempted to measure performance on their own setup, looking for combinations of game settings that sit below the 3.5GB threshold and those that cross above it, into the slower 500MB portion. The issue for many of these tests is that they lack access to both a GTX 970 and a GTX 980 to really compare performance degradation between cards. That's the real comparison to make - the GTX 980 does not separate its 4GB into different memory pools. If it has performance drops in the same way as the GTX 970 then we can wager the memory architecture of the GTX 970 is not to blame. If the two cards perform differently enough, beyond the expected performance delta between two cards running at different clock speeds and with different CUDA core counts, then we have to question the decisions that NVIDIA made.
There has also been concern over the frame rate consistency of the GTX 970. Our readers are already aware of how deceptive an average frame rate alone can be, and why looking at frame times and frame time consistency is so much more important to guaranteeing a good user experience. Our Frame Rating method of GPU testing has been in place since early 2013 and it tests exactly that - looking for consistent frame times that result in a smooth animation and improved gaming experience.
Users at reddit.com have been doing a lot of subjective testing
We will be applying Frame Rating to our testing today of the GTX 970 and its memory issues - does the division of memory pools introduce additional stutter into game play? Let's take a look at a couple of examples.
A few secrets about GTX 970
UPDATE 1/28/15 @ 10:25am ET: NVIDIA has posted in its official GeForce.com forums that they are working on a driver update to help alleviate memory performance issues in the GTX 970 and that they will "help out" those users looking to get a refund or exchange.
Yes, that last 0.5GB of memory on your GeForce GTX 970 does run slower than the first 3.5GB. More interesting than that fact is the reason why it does, and why the result is better than you might have otherwise expected. Last night we got a chance to talk with NVIDIA’s Senior VP of GPU Engineering, Jonah Alben on this specific concern and got a detailed explanation to why gamers are seeing what they are seeing along with new disclosures on the architecture of the GM204 version of Maxwell.
NVIDIA's Jonah Alben, SVP of GPU Engineering
For those looking for a little background, you should read over my story from this weekend that looks at NVIDIA's first response to the claims that the GeForce GTX 970 cards currently selling were only properly utilizing 3.5GB of the 4GB frame buffer. While it definitely helped answer some questions it raised plenty more which is whey we requested a talk with Alben, even on a Sunday.
Let’s start with a new diagram drawn by Alben specifically for this discussion.
GTX 970 Memory System
Believe it or not, every issue discussed in any forum about the GTX 970 memory issue is going to be explained by this diagram. Along the top you will see 13 enabled SMMs, each with 128 CUDA cores for the total of 1664 as expected. (Three grayed out SMMs represent those disabled from a full GM204 / GTX 980.) The most important part here is the memory system though, connected to the SMMs through a crossbar interface. That interface has 8 total ports to connect to collections of L2 cache and memory controllers, all of which are utilized in a GTX 980. With a GTX 970 though, only 7 of those ports are enabled, taking one of the combination L2 cache / ROP units along with it. However, the 32-bit memory controller segment remains.
You should take two things away from that simple description. First, despite initial reviews and information from NVIDIA, the GTX 970 actually has fewer ROPs and less L2 cache than the GTX 980. NVIDIA says this was an error in the reviewer’s guide and a misunderstanding between the engineering team and the technical PR team on how the architecture itself functioned. That means the GTX 970 has 56 ROPs and 1792 KB of L2 cache compared to 64 ROPs and 2048 KB of L2 cache for the GTX 980. Before people complain about the ROP count difference as a performance bottleneck, keep in mind that the 13 SMMs in the GTX 970 can only output 52 pixels/clock and the seven segments of 8 ROPs each (56 total) can handle 56 pixels/clock. The SMMs are the bottleneck, not the ROPs.
A new GPU, a familiar problem
Editor's Note: Don't forget to join us today for a live streaming event featuring Ryan Shrout and NVIDIA's Tom Petersen to discuss the new GeForce GTX 960. It will be live at 1pm ET / 10am PT and will include ten (10!) GTX 960 prizes for participants! You can find it all at http://www.pcper.com/live
There are no secrets anymore. Calling today's release of the NVIDIA GeForce GTX 960 a surprise would be like calling another Avenger's movie unexpected. If you didn't just assume it was coming chances are the dozens of leaks of slides and performance would get your attention. So here it is, today's the day, NVIDIA finally upgrades the mainstream segment that was being fed by the GTX 760 for more than a year and half. But does the brand new GTX 960 based on Maxwell move the needle?
But as you'll soon see, the GeForce GTX 960 is a bit of an odd duck in terms of new GPU releases. As we have seen several times in the last year or two with a stagnant process technology landscape, the new cards aren't going be wildly better performing than the current cards from either NVIDIA for AMD. In fact, there are some interesting comparisons to make that may surprise fans of both parties.
The good news is that Maxwell and the GM206 GPU will price out starting at $199 including overclocked models at that level. But to understand what makes it different than the GM204 part we first need to dive a bit into the GM206 GPU and how it matches up with NVIDIA's "small" GPU strategy of the past few years.
The GM206 GPU - Generational Complexity
First and foremost, the GTX 960 is based on the exact same Maxwell architecture as the GTX 970 and GTX 980. The power efficiency, the improved memory bus compression and new features all make their way into the smaller version of Maxwell selling for $199 as of today. If you missed the discussion on those new features including MFAA, Dynamic Super Resolution, VXGI you should read that page of our original GTX 980 and GTX 970 story from last September for a bit of context; these are important aspects of Maxwell and the new GM206.
NVIDIA's GM206 is essentially half of the full GM204 GPU that you find on the GTX 980. That includes 1024 CUDA cores, 64 texture units and 32 ROPs for processing, a 128-bit memory bus and 2GB of graphics memory. This results in half of the memory bandwidth at 112 GB/s and half of the peak compute capability at 2.30 TFLOPS.
There are smart people that work at AMD. A quick look at the company's products, including the APU lineup as well as the discrete GPU fields, clearly indicates a lineup of talent in engineering, design, marketing and business. It's not perfect of course, and very few companies can claim to be, but the strengths of AMD are there and easily discernible to those of us on the outside looking in with the correct vision.
Because AMD has smart people working hard to improve the company, they are also aware of its shortcomings. For many years now, the thorn of GPU software has been sticking in AMD's side, tarnishing the name of Radeon and the products it releases. Even though the Catalyst graphics driver has improved substantially year after year, the truth is that NVIDIA's driver team has been keeping ahead of AMD consistently in basically all regards: features, driver installation, driver stability, performance improvements over time.
If knowing is half the battle, acting on that knowledge is at least another 49%. AMD is hoping to address driver concerns now and into the future with the release of the Catalyst Omega driver. This driver sets itself apart from previous releases in several different ways, starting with a host of new features, some incremental performance improvements and a drastically amped up testing and validation process.
AMD considers this a "special edition" driver and is something that they plan to repeat on a yearly basis. That note in itself is an interesting point - is that often enough to really change the experience and perception of the Catalyst driver program going forward? Though AMD does include some specific numbers of tested cases for its validation of the Omega driver (441,000+ automated test runs, 11,000+ manual test runs) we don't have side by side data from NVIDIA to compare it to. If AMD is only doing a roundup of testing like this once a year, but NVIDIA does it more often, then AMD might soon find itself back in the same position it has been.
UPDATE: There has been some confusion based on this story that I want to correct. AMD informed us that it is still planning on releasing other drivers throughout the year that will address performance updates for specific games and bug fixes for applications and titles released between today and the pending update for the next "special edition." AMD is NOT saying that they will only have a driver drop once a year.
But before we worry about what's going to happen in the future, let's look into what AMD has changed and added to the new Catalyst Omega driver released today.