Windows 7: Performance

But, when we subjected Windows 7 to our Real World Benchmarks, we received some surprising results. The most obvious anomaly was our Office benchmark, which took more than 70 percent longer to complete on the new OS than in Vista.

This also affected the multi-application test, of which Office is one component, and had a knock-on effect on the overall score. In our other tests, Windows 7 did prove faster than Vista - but only by a margin of around 2 percent. In everyday use this difference is undetectable; so how can this be squared with our experience of Windows 7 feeling faster than Vista?

It comes down to Windows Display Driver Model 1.1, which is new in Windows 7. The model permits multiple apps to draw and update their graphics at once, whereas under the 1.0 model used in Vista only a single process could draw to the screen at any one time. This was a prime reason why the interface could sometimes feel unresponsive.

On Windows 7, apps can update their windows as soon as you press a button. The system thus feels much faster, while measurable performance is similar.

The office benchmark
So what went wrong with our Office benchmark? The answer is down to another change in WDDM 1.1. In Vista, display elements were stored concurrently in both video RAM (accessible via the graphics hardware) and system RAM (accessible by the OS), while WDDM 1.1 uses video RAM only.

This leaves more system memory free for applications, but it also means that if the OS wants to draw graphics without going via the GPU, the relevant elements must be copied from video RAM to system RAM and back.

This may sound like a tiny imposition, but it takes quite a toll on the PowerPoint segment of our benchmark, which is designed to render slides as quickly as possible. Under Windows 7, the delay causes each slide to take more than twice as long to render as it does under Vista. Over 500 slides, the cumulative effect wrecks the overall Office score.

To the human eye, the slower redraw rate is barely noticeable, but if you need to revert to the old way of doing things for any reason, you can. Windows 7's Basic Theme effectively turns off WDDM 1.1 off, and we'll be using this approach to run the Office portion of our benchmarks, in order to achieve scores comparable to older machines.

Less demanding
The reduced RAM footprint is particularly helpful for netbooks and nettop devices, which can ship with as little as 1GB. For comparison, we repeated our benchmarks with only 1GB of RAM in both Vista and Windows 7. In Vista, we saw a 12 percent drop in overall performance, reflecting a one percent slowdown in the CPU-based encoding test, a 12 percent fall in the Office test, a 13 percent drop-off in 2D graphics, and a massive 23 percent slowdown in our multitasking test.

In Windows 7, performance with 1GB held up better: again, the multitasking test was worst hit, but it fell by only 12% percent. The encoding, Office and 2D graphics scores fell by one percent, six percent and nine percent, yielding an overall drop of only seven percent. Factor in the faster UI and it's clear Windows 7 is a better choice for low-end hardware.
DirectX 11

As well as improvements on the desktop, Windows 7 ships with the all-new DirectX 11, which, when partnered with a compatible graphics card (such as the ATI Radeon HD 5870), will enable games to take advantage of more advanced effects than ever before.

DirectX 11 also includes a raft of new computational features, enabling developers to write complex programs designed to be executed on the GPU. This will speed up certain types of operation enormously: in some cases, GPU-based video encoding can be more than ten times as fast as CPU-only routines.

But DirectX 11 isn't restricted to Windows 7. DirectX 10 was never released for Windows XP, but its successor is due to be back-ported to Vista, so there's no need to upgrade to get the full benefit of newer, more powerful graphics hardware. However, there aren't yet any games that take advantage of DirectX 11. And when we tested DirectX 10 games on Windows 7, performance was identical to Vista.

Network performance
Windows 7 offers a small improvement over Vista in networking too. In our tests, reading 200MB of small files from a remote PC over 100Mbits/sec Ethernet took our Vista system 47 seconds, while Windows 7 managed it in 40 seconds. Copying the files back took an identical 1min 26secs, regardless of the client OS.
That's a small benefit, but given how much underlying code Windows 7 shares with Vista, it's impressive that there's any speed boost at all. And we're encouraged to note that, although the beta and release candidate builds of Windows 7 have been available for more than nine months, we've heard no reports of it inheriting the slow network performance that mysteriously afflicts some Vista users.

Conclusion
So, our tests show that, when it comes to raw number-crunching, Windows 7 is negligibly faster than the older OS. It certainly doesn't retu0rn to the speed of Windows XP, which in our benchmarks has proved as much as 22 percent faster than Vista on identical hardware.

Couple that with the fact that DirectX 11 will be available in Vista, and you'd be forgiven for concluding there's no point upgrading from a performance perspective.

But don't underestimate the importance of responsiveness. The upgraded driver model makes Windows 7 applications seem to fly along, where Vista could sometimes feel like wading through treacle. Don't be put off by the alarming graph on the previous page: in real-world use you'll be more productive simply because it's easier to click around, and less frustrating to get things done.

Windows 7 won't magically turbo-charge your hardware then, but it's still a genuine step forward when it comes to making the most of your computer's potential.