Mobile GPU Faceoff: AMD Dynamic Switchable Graphics vs. NVIDIA Optimus Technology

Let’s Talk About Drivers

So what does our discussion of gaming compatibility and performance really mean? First, let’s start by looking at the AMD driver version. The CCC version used by Sony appears to date from February 4, 2011 (software version 8.811.1.5-110204a-115635C-Sony), so best-case we’re looking at bits and pieces from the Catalyst 11.2 era, but mostly 11.1. Ouch. There are also oddities with the Sony driver release where sometimes not all CCC options are available (e.g. the Information tab doesn't always show up). CCC also crashed a few times when switching between manual and dynamic modes (or IGP and GPU modes when in manual switching). Given how old the Sony drivers are, many of the lower-than-expected performance results (particularly in the recent titles list) should improve with something like the Catalyst 11.8 drivers. That right there is reason enough to consider bypassing any laptop where you can’t get up to date drivers from the GPU manufacturer, and Sony completely misses the boat with their AMD-equipped laptops.

For any consumer notebook with a discrete GPU, if the GPU is actually supposed to be useful over the long haul, owners need the ability to get regular driver updates. For games in particular, in some cases driver updates can mean the difference between running properly or not at all; in other instances, a new driver might increase performance by as much as 20% or more, especially on new releases. And lest anyone get the idea that I’m just picking on AMD’s mobile drivers, let me refer back to something I wrote in 2008 (and substitute “gaming” for “SLI”): “Honestly, what we really need is the ability to run reference drivers on gaming laptops - even more so than regular laptops, although that would also be great. As far as we're concerned, a gaming notebook needs to be as seamless as a desktop when it comes to updating drivers and running games. Until that happens, we would think very carefully before spending a lot of money on gaming laptop.”

I took NVIDIA to task for their lack of generic driver updates over three years ago, and over the next two years we saw the situation improve with their Verde program, Optimus Technology, and then the two combined so that virtually all NVIDIA-equipped laptops (a few business-centric laptops may not qualify) can get new drivers the same day that desktop drivers launch. Today it's time to give AMD and Sony the same treatment. For Sony, I really see no point in shipping a laptop with a discrete GPU and then doing nothing with the drivers; long-term, you might as well just sell the laptop with an Intel IGP rather than going after the checkbox feature.

AMD has a similar program to NVIDIA’s Verde, but notably absent from the program are the following: laptops with switchable graphics and Intel chipsets, Toshiba notebooks, Sony notebooks, and Panasonic notebooks. Thus, Sony gets a double fail on the driver situation with the VAIO C: once for not participating in AMD’s mobile driver program at all (for non-switchable laptops), and the second they get to share blame with AMD (for switchable graphics). Simply put, NVIDIA has the better approach: provide reference drivers for nearly all laptops that use NVIDIA GPUs, and include support for laptops with Optimus graphics switching technology. (Incidentally, if you look at the latest NVIDIA driver release notes, Hybrid Power laptops aren’t supported, since they use manual graphics switching technology similar to AMD’s switchable graphics, and only a couple Sony laptops are supported. Fujitsu laptops are also on the unsupported list.)

UI Concerns

I brought up my concerns with AMD in regards to their mobile drivers prior to writing this article. Their general stance is that they want to make things “easy” by not overwhelming users with too much information. For advanced users (like myself and many of our readers), they can fall back to the fixed function switchable graphics (i.e. manual mode). My major gripe is that making things easy apparently means not providing a global list of applications/games with profiles—something we’ve been asking them to add since CrossFire first hit the scene! Just to be clear, I strongly disagree with their “easy” suggestion, because using the VAIO C made it patently clear that this is not easier than using an Optimus-based laptop. Here’s why.

It’s true that you can switch between dynamic (application based) switching and manual switching, but as I’ve discussed earlier, there are instances for both sides where games don’t work quite right. The solution thus becomes one of opening the CCC, selecting the appropriate mode (there’s no quick way to tell which mode you’re in outside of the CCC), and then you can load the game. First, I have to say that opening AMD’s Catalyst Control Center and switching between dynamic and manual modes is hardly ideal—in fact, it can often be a bit of a pain. Particularly on this Sony laptop, I’ve noticed that the CCC frequently takes far too long to load—I’ve seen it take upwards of 30 seconds on a regular basis! A slow hard drive with a bloated .NET interface appears to be the issue, but whatever the cause (an old driver as well?), it can be annoying.

There’s also the question of what games are supposed to work properly, and there’s no global source you can consult for this information (at least, not that I could find). AMD can call it overwhelming if they want, but NVIDIA’s drivers make it really easy to see if a game at least should work with Optimus (though even unlisted games have worked in my experience so far). AMD’s application based switching looks for anything using DirectX calls as far as I can tell, which results in things like dialogs asking whether Explorer.exe should run on the Power Saving GPU or the High Performance GPU. Perhaps that’s a better definition of overwhelming: popping up dialogs that aren’t necessary? Early on in testing, I turned off the “prompt every time a new graphics application runs” option; if you want to get it back, however, you’ll need to restore the default settings as there’s no box to uncheck. Either way, the first time you launch a graphics-enabled application, it’s given a “Not Assigned” classification, which appears to be about 50-50 in terms of running on the IGP or running on the GPU.

In general, I found the manual switching mode to be the better AMD solution right now—only DiRT 3 had a major issue there. Contrast that with minor to major annoyances in Super Street Fighter IV: Arcade Edition, StarCraft II, and all OpenGL titles not working with the application-based switching and there’s really no point in dynamic switching. But then, we’re also looking at drivers from over seven months back, apparently, so perhaps things are better—we couldn’t check, as we don’t have another laptop with AMD’s switchable graphics and a more recent driver available. Even if you skip dynamic switching, manual switching isn’t a great experience either, since the screen will flash and go blank for 5-10 seconds every time you switch between the IGP and GPU. Granted, in most cases the only time you’d actually need to do that would be when going from AC power to battery power—get the switching to happen faster and get me regular driver updates and I’d be fine with manual control.

Other Requests

When I first laid hands on a laptop with switchable graphics, I predicted that such a design would become the future for mobile GPUs. Really, if everything works properly on a low-end or mid-range GPU, there’s no reason it shouldn’t work on high-end GPUs as well. Once that happens, there’s a good incentive for notebook manufactures to use graphics switching on every mobile product that has a dedicated GPU.

This is precisely what we’ve seen with NVIDIA’s mobile lineup. Starting with the 200M, we saw only a couple laptops with Optimus or some other form of switchable graphics. The 300M is when Optimus really gained traction on virtually all the mainstream laptops, and with 400M we started to see higher performance mobile GPUs with Optimus support. Now their 500M even has a few vendors (e.g. Alienware M17x) that use Optimus on their top-end GTX 580M.

For AMD, right now it looks like the only laptops with dynamic switchable graphics use either the HD 6400M or the HD 6600M/6700M (same chip at different clocks). The HD 6470M is almost superfluous these days, considering Intel’s HD 3000 is within striking distance (and Ivy Bridge will apparently close the gap). Meanwhile, the 6300M, 6500M, and 6800M are just renamed 5400M/5600M/5800M chips, so they apparenlty lack the necessary hardware change to do dynamic switching. It's not clear whether 6900M can support dynamic switching, and high-end GPUs could certainly benefit (assuming the bugs and other issues are worked out), but no one is doing it. Perhaps it’s just a case of the chicken and the egg: if AMD gets dynamic switching to work properly on all their mobile GPUs, vendors would be a lot more likely to use the technology on high-end laptops.

With all my talk of switchable graphics, though, let’s make one thing clear: switchable graphics is not necessarily the Holy Grail of mobile GPUs. The true ideal in my opinion is mobile GPUs that can run fast when needed (i.e. playing games), while also being able to power off large portions of the chip and RAM and get down to IGP levels of power consumption. The GTX 580M for instance has 384 CUDA cores divided into eight Shader Modules, with a 256-bit memory controller divided into four 64-bit interfaces. When playing games or doing other intensive graphics/computational work, the GTX 580M can use up to 100W of power. At idle, we estimate power consumption to be around 16W, which obviously takes a toll on battery life.

Imagine if the GTX 580M could fully shut down seven of the eight SMs and three of the four memory interfaces, as well as doing some voltage and clock speed modifications. Do we need more than 48 CUDA cores and a 64-bit memory interface for the Windows desktop? Most likely not. It’s possible with the right design, we could get a dedicated GPU that would idle at less than 1W—similar to current IGPs. If we can get that, then there’s no actual need for graphics switching technology; you’d get the best of both worlds. But until and unless we reach that point, technologies like Optimus and dynamic switchable graphics are the next best thing—at least when everything works properly. Of course, with AMD’s APUs and Intel putting faster IGPs into their CPU packages, focusing on switchable graphics makes a lot of sense. Going forward, nearly every consumer CPU is going to have some form of on-die graphics, so why not put it to good use?