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Windows 7 Way Smarter With Graphics RAM

By - Source: Tom's Hardware US | B 9 comments

New Windows 7 WDDM 1.1 drivers save you RAM

In an earlier article, we described an advancement that the Windows 7 team made with desktop graphics by allowing more than one application to access the GDI (graphics device interface) stack at a time.

Allowing for more parallelism in the GDI will noticeably make things more responsive, but that wasn’t the only evolution that the software team made for the new OS. Windows 7 will now be more efficient in its use of RAM, which will have the positive effect of making everything run smoother – particularly on systems with shared graphics memory.

In Windows Vista, the more application windows you had open, the more memory required. Every window accounts for two memory allocations – one in video memory and one in system memory – which hold identical content.

The DWM (desktop window manager) is responsible for drawing the desktop with the GPU, which obviously requires the application window data in video memory. The same application window data is duplicated again in system RAM for the CPU to render independent of graphics hardware. This was inefficient obviously because of data redundancy.

Windows 7 changes this by getting rid of the system memory copy entirely, which effectively cuts the memory consumed in half. Unlike the changes to the GDI stack detailed earlier, this new memory-saving behavior requires new drivers.

“We achieved the reduction in system memory by accelerating the common GDI operations through the graphics hardware - the WDDM drivers accelerate these to minimize the performance impact of the CPU read-back of video memory,” explained Ameet Chitre, a program manager on Microsoft’s Desktop Graphics feature team. “Since you save a lot of system memory, the paging activity gets reduced – as a result, your system responsiveness improves for the same workload.”

The new drivers that support the memory-saving change are designated WDDM 1.1. Older Windows Vista WDDM 1.0 drivers will still work fine with Windows 7, but do not take advantage of the new feature.

This change positively impacts real-world usability, but benchmarks may show a degradation in performance since the CPU has to fetch data from video RAM.

“The elimination of the duplicate system memory copies which ‘speed up’ certain operations introduced slightly reduced performance as the CPU now has to read data back from the video memory. An analysis of real-world application statistics showed that these operations were rare,” Chitre said. “Our observation has been that these slow-downs do not impact the end-user functionality directly and that the memory savings directly result in Windows 7 being much responsive overall.  The improvements overall are definitely noticeable on memory constrained PCs with shared memory graphics.”

The close-to-completion Windows 7 is nearly upon us. We learned on Saturday that the Release Candidate will be hitting MSDN and TechNet subscribers on April 30 with the public getting their Windows 7 RC download links on May 5.

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  • 0 Hide
    waxdart , 28 April 2009 17:43
    There is nothing about windows 7 that seems worth paying for. Windows xp flops along with not much hassle. I bought a laptop that came with vista installed. I hate it, every task is a pain. I would downgrade to XP; but its purpose is to allow me to familiarise myself with vista! The next few years would need to give rave reviews from 99% of users for me to want to bother with win7.
  • 0 Hide
    caskachan , 28 April 2009 19:17
    "The same application window data is duplicated again in system RAM for the CPU to render independent of graphics hardware. This was inefficient obviously because of data redundancy."

    mmh.. O REALLY?

    yet they went ahead when they made vista.. sigh...

    wonder if they fixed , other "OOPS"
  • 0 Hide
    Anonymous , 28 April 2009 19:36
    Three months ago, I bought a Toshiba Laptop with genuine Windows Vista Home Premium installed. I also assembled a desktop pc with Windows XP SP2 as the operating system. Since I am curious about Vista, I opened my two computers at the same time and runs the same programs. I did it a hundred times so that I can determine which OS can run programs faster and smoohtly. I found out that XP runs programs better without much hassles compared to Vista. ButI still use Vista to familiarize its new features but in running programs, I really preferred Windows XP. Howard 2009
  • 0 Hide
    Anonymous , 28 April 2009 19:54
    I hope that Microsoft Corporation will extend their support on Windows XP beyond 2014. This operating system is powerful, user friendly, and their troubleshooting help in Help and Support panes is very helpful and easy to follow. Well thanks to Microsoft for Inventing programs that the made the world better and helping people in different corners of the planet closer. God bless bless Microsoft Corporation.
  • 0 Hide
    LePhuronn , 28 April 2009 20:12
    Although the complaints about Vista are valid and very true, the whole reason people are excited about 7 is because Microsoft have seemingly done it right. Yes the codebase is the same, but 7 is NOT Vista.

    Don't let that monstrosity affect your impressions of 7 negatively, in fact if you hate Vista then you simply must upgrade to 7 (or so the hype is saying).

    Personally I'm quite proud of the fact I've leapfrogged a Windows generation and totally avoided Vista - by the time my new rig comes to life 7 will be with us and I'd never darken my days with the big V.
  • 0 Hide
    Anonymous , 28 April 2009 21:03
    I use Vista on 3 computers without ever having a single issue. All this bad press must be leftovers from before sp1. People like Lephuronn hear bad things and repeat them without ever actually using it. Sorry i think Vista was a nice improvement over Xp. Not saying it was "omg 0wn" impressive but i deffinetly dont see it as the train wreck people make it out to be.
  • 0 Hide
    tstebbens , 28 April 2009 23:45
    @howard_08

    How can you possibly compare Vista running on a laptop to XP running on a desktop? Mobile processor performance will vary, XP will likely not have power saving features enabled, laptop will likely have a slower hard disk, etc, etc, etc. You would need to compare the two running side-by-side on identical hardware.

    @caskachan

    They also did it in XP... and 2000, Me, 98, 95, etc, etc. for that matter

    The fact is, if you turn off UAC and Aero, Vista is at least equal in performance to XP - faster in many cases (boot up being one.) Some things (like the Network Sharing Centre) are a pain compared to XP, but then others are much much better (like the Start menu search for instance.) So it's swings and roundabouts. Certainly no reason to get Vista if XP is working for you, but there's no need to jump on the anti-Vista bandwagon for unfounded reasons.

    I for one have found Vista much more stable on my platform than XP ever was. XP used to BSoD every few days for no reason because of USB or graphics driver problems. With Vista I haven't had a single crash. Longest uptime (between reboots for updates) was ~60 days which for a gaming machine is pretty damn good.
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    LePhuronn , 29 April 2009 01:26
    @SininStyle:

    I'm sorry, but what??? You think I've never used it? Just because I've skipped owning it and thusly never had to shell out for it doesn't mean I have no exposure to it. In fact, if you care to look up any of my previous posts throughout this site you'd see that any negative opinion I have of Vista is based ENTIRELY on using it.

    I'm ecstatic that your experiences with Vista have been good ones - well done you! Mine have always been terrible on everything from low-end Acer laptops to Quad-core, multi-gig media development rigs and everything in between.

    Kindly don't presume that I don't know what I'm talking about just because I said I "leapfrogged a generation".
  • 0 Hide
    Anonymous , 29 April 2009 09:13
    Can Vista SP2 has WDDM 1.1?