A Brief History of Switchable Graphics

So what is Optimus exactly? You could call it NVIDIA Switchable Graphics III, but that makes it sound like only a minor change. After our introduction, in some ways the actual Optimus technology is a bit of a letdown. This is not to say that Optimus is bad—far from it—but the technology only addresses a subset of our wish list. The area Optimus does address—specifically switching times—is dealt with in what can only be described as an ideal fashion. The switch between IGP and discrete graphics is essentially instantaneous and transparent to the end-user, and it's so slick that it becomes virtually a must-have feature for any laptop with a discrete GPU. We'll talk about how Optimus works in a minute, but first let's discuss how we got to our present state of affairs.

It turns out that the Optimus hardware has been ready for a while, but NVIDIA has been working hard on the software side of things. On the hardware front, all of the current G200M and G300M 40nm GPUs have the necessary internal hardware to support Optimus. Earlier laptop designs using those GPUs don't actually support the technology, but the potential was at least there. The software wasn't quite ready, as it appears to be quite complex—NVIDIA says that the GeForce driver base now has more lines of code than Windows NT, for example. NVIDIA was also keen to point out that they have more software engineers (over 1000) than hardware engineers, and some of those software engineers are housed in partner offices (e.g. there are NVIDIA employees working over at Adobe, helping with the Flash 10.1 software). Anyway, the Optimus hardware and software are both ready for public release, and you should be able to find first Optimus enabled laptops for sale starting today.


The original switchable graphics designs used a hardware switch to allow users to select either an IGP or discrete GPU. The first such system that we tested was the ASUS N10JC, but the very first implementation came from Sony in the form of the VAIO SZ-110B launched way back in April 2006. (The Alienware m15x was also gen1 hardware.) Generation one required a system reboot in order to switch between graphics adapters, with hardware multiplexers routing power to the appropriate GPU and more multiplexers to route the video signal from either GPU to the various display outputs. On the surface, the idea is pretty straightforward, but the actual implementation is much more involved. A typical laptop will have three separate video devices: the laptop LCD, a VGA port, and a DVI/HDMI port. Adding the necessary hardware requires six (possibly more) multiplexer ICs at a cost of around $1 each, plus more layers on the motherboard to route all of the signals. In short, it was expensive, and what's worse the required system reboot was highly disruptive.

Many users of the original switchable graphics laptops seldom switched, opting instead to use either the IGP or GPU all the time. I still liked the hardware and practically begged manufacturers to include switchable graphics in all future laptop designs. My wish wasn't granted, although given the cost it's not difficult to see why. As far as the rebooting, my personal take is that it was pretty easy to simply switch your laptop into IGP mode right before spending a day on the road. If you were going to spend most of the day seated at your desk, you'd switch to discrete mode. The problem is, as one of the highly technical folks on the planet, I'm not a good representation of a typical user. Try explaining to a Best Buy shopper exactly what switchable graphics is and how it works, and you're likely to cause more confusion than anything. Our readers grasp the concept, but the added cost for a feature many wouldn't use meant there was limited uptake.


Generation two involved a lot more work on the software side, as the hardware switch became a software controlled switch. NVIDIA also managed to eliminate the required system reboot (although certain laptop vendors continue to require a reboot or at least a logout, e.g. Apple). Again, that makes it sound relatively simple, but there are many hurdles to overcome. Now the operating system has to be able to manage two different sets of drivers, but Windows Vista in particular doesn't allow multiple display drivers to be active. The solution was to create a "Display Driver Interposer" that had knowledge of both driver sets. Launched in 2008, the first laptop we've reviewed with gen2 hardware and software was actually the ASUS UL80Vt, which took everything we loved about gen1 and made it a lot more useful. Now there was no need to reboot the system; you could switch between IGP and dGPU in about 5 to 10 seconds, theoretically allowing you the best of both worlds. We really liked the UL80Vt and gave it our Silver Editors' Choice award, but there was still room for improvement.

First, the use of a driver interposer meant that generic Verde drivers would not work with switchable graphics gen2. The interposer conforms to the standard graphics APIs, but then there's a custom API to talk to the IGP drivers. The result is that the display driver package contains both NVIDIA and Intel drivers (assuming it's a laptop with an Intel IGP), so driver updates are far more limited. If either NVIDIA or Intel release a new driver, there's an extra ~10 days of validation and testing that take place; if all goes well, the new driver is released, but any bugs reset the clock. Of course, that's only in a best-case situation where NVIDIA and Intel driver releases happen at the same time, which they rarely do. In practice, the only time you're likely to get a new driver is if there's a showstopper bug of some form and the laptop OEM asks NVIDIA for a new driver drop. This pretty much takes you back to the old way of doing mobile graphics drivers, which is not something we're fond of.

Another problem with gen2 is that there are still instances where switching from IGP to dGPU or vice versa will "block". Blocking occurs when an application is in memory that currently uses the graphics system. If blocking was limited to 3D games it wouldn't be a critical problem, but the fact is blocking can occur on many applications—including minesweeper and solitaire, web browsers where you're watching (or have watched) Flash videos, etc. If a blocking application is active, you need to close it in order to switch. The switch also results in a black screen as the hardware shifts from one graphics device to the other, which looks like potentially flaky hardware if you're not expecting the behavior. (This appears to be why Apple MacBook Pro systems require a reboot/logout to switch, even though they're technically gen2 hardware.) Finally, it's important to note that gen2 costs just as much as gen1 in terms of muxes and board layers, so it can still increase BOM and R&D costs substantially.

Incidentally, AMD switchable graphics is essentially equivalent to NVIDIA's generation two implementation. The HP Envy 13 is an example of ATI switchable graphics, with no reboot required and about 5-10 seconds required to switch between IGP and discrete graphics (an HD 4330 in this case—and why is it they always seem to use the slowest GPUs; why no HD 4670?).

For technically inclined users, gen2 was a big step forward and the above problems aren't a big deal; for your typical Best Buy shopper, though, it's a different story. NVIDIA showed a quote from Roger Kay, President of Endpoint Technology Associates, that highlights the problem for such users.

"Switchable graphics is a great idea in theory, but in practice people rarely switch. The process is just too cumbersome and confusing. Some buyers wonder why their performance is so poor when they think the discrete GPU is active, but, unknown to them, it isn't."

The research from NVIDIA indicates that only 1% of users ever switched between IGP and dGPU, which frankly seems far too low. Personally, if a laptop is plugged in then there's no real reason to switch off the discrete graphics, and if you're running on battery power there's little reason to enable the discrete graphics most of the time. It could be that only 1% of users actually recognize that there's a switch taking place when they unplug their laptop; it could also be that MacBook Pro users with switchable graphics represented a large percentage of the surveyed users. Personally, I am quite happy with gen2 and my only complaint is that not enough companies use the technology in their laptops.

Index NVIDIA Optimus Unveiled
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  • jkr06 - Saturday, February 27, 2010 - link

    From all the articles I read, one thing is still not clear to me. I have a laptop with core i5(which has IGP) and nvidia 330M. So can I utilize the optimus solution with just SW. Or the laptop manufacturers specifically need to add something to truly make it work. Reply
  • JonnyDough - Friday, February 19, 2010 - link

    was a wasted effort. Seems sort of silly to switch between two GPU's when you can just use one powerful one and shut off parts of it. Reply
  • iwodo - Thursday, February 18, 2010 - link

    First, the update, they should definitely set up something like Symantec or Panda Cloud Database, where users input are stored and shared and validated worldwide. The amount of games that needs to be profiled is HUGE. Unless there is a certain simple and damn clever way of catching games. Inputting every single games / needed apps running exe names sounds insane to me. There has to be a much better way to handle this.

    I now hope Intel would play nice, and gets a VERY power efficient iGPU inside SandyBridge to work with Optimus, Instead of botching even more transistors for GPU performance.
    Reply
  • secretanchitman - Saturday, February 13, 2010 - link

    any chance of this going to the macbook pros? im hoping when they get updated (soon i hope), it will have some form of optimus inside. if not, something radeon based. Reply
  • strikeback03 - Thursday, February 11, 2010 - link

    As I don't need a dGPU, I would like to see a CULV laptop with the Turbo33 feature but without any dGPU in order to save money. Maybe with Arrandale. Reply
  • jasperjones - Wednesday, February 10, 2010 - link

    Jarred,

    As you imply, graphics drivers are complex beasts. It doesn't make me happy at all that now Optimus makes them even more complex.

    Optimus will likely require more software updates (I don't think it matters whether they are called "driver" or "profile" updates).
    That puts you even more at the mercy of the vendor. Even prior to Optimus, it bothered me that NVIDIA's driver support for my 3 1/2 year old Quadro NVS 110m is miserable on Win 7. But, with Optimus, it is even more critical to have up-to-date software/driver support for a good user experience! Furthermore, software solutions are prone to be buggy. For example, did you try to see if Optimus works when you run virtual machines?

    Also, I don't like wasting time installing updates. Why can't GPUs just work out of the box like CPUs?

    Lastly, these developments are completely contrary to what I believe are necessary steps towards more platform independence. Will NVIDIA ever support Optimus on Linux? While I suspect the answer is yes, I imagine it will take a year and a half at the very least.
    Reply
  • obiwantoby - Wednesday, February 10, 2010 - link

    I think it is important to note, that the demo video, even though it is a .mov, works in Windows 7's Windows Media Player. It works quite well, even with hardware acceleration.

    Keep encoding videos in h.264, it works on both platforms in their native players.

    No need for Quicktime on Windows, thank goodness.
    Reply
  • dubyadubya - Wednesday, February 10, 2010 - link

    "Please note that QuickTime is required" FYI Windows 7 will play the mov file just fine so no need for blowtime. Why the hell would anyone use a codec that will not run on XP or Vista without Blowtime is beyond me. For anyone wanting to play mov files on XP or Vista go get Quicktime alternative. Reply
  • beginner99 - Wednesday, February 10, 2010 - link

    Did I read that right, HD video is always decoded on the dGPU even if the (Intel) IGP could deal with it?

    I mean it sounds nice but is there also an option prevent certain apps from using de dGPU?

    Or preventing the usage of dGPU completely like when one really needs the longest battery time possible? -> some users like to have control themselves.
    intel IGP might offer worse quality with their videao decode feature (but who really sees that on laptop lcd?) but when travelling the whole day and watching movies, I would like to use as little power as possible.
    Reply
  • JarredWalton - Wednesday, February 10, 2010 - link

    It sounds like this is really just a case of the application needing a "real profile". Since I test x264 playback using MPC-HC, I had to create a custom profile, but I think that MPC-HC detected the GMA 4500MHD and decided that was perfectly acceptable. I couldn't find a way to force decoding of an .mkv x264 video within MPC-HC, but other video playback applications may fare better. I'll check to see what happens with WMP11 as well tomorrow (once I install the appropriate VFW codec). Reply

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