How does the performance rating work?

From Ed's mailbag: When you install Windows Vista, it runs a System Assessment Tool and gives your computer a performance rating called the Windows Experience Index. What does that number mean? What kind of hardware gets a perfect score

I've been getting great questions about Windows Vista via e-mail lately and thought I would answer a few of them here. If I keep getting good questions, I'll make this a regular feature.

Yesterday, Stefan asked about the "Windows Vista System Performance Grade":

I don't understand the scale really. How it works, what a 1 is, what a 10 is, and I can't find information on these topics ... It's frustrating.

Can you possibly send some links my way, or find out, how the hell in the world this scaling system works and what it would take to get a perfect score (whatever that number might be?)

The Windows Vista System Assessment Tool runs at installation time (and later, if you change hardware) and produces an overall rating of your hardware called the Windows Experience Index. In August, my ZDNet colleague Adrian Kingsley-Hughes put together a really great, in-depth look at the Windows Experience Index based on an earlier beta release. Adrian’s post is a good companion to Vista Mythbusters #1: It’s not a hardware hog.

The most definitive explanation I've seen so far is Windows Experience Index: An In-Depth Look, on the Windows Vista Team Blog. It explains what goes into the 5 sub-scores, each of which can range from 1 to 5.9 (higher is better). The lowest of the sub-scores becomes the base score. So the system whose index is shown here has a smokin' hard disk, fast RAM, and a decent CPU, so it gets scores of 5.1 or better in all those categories. But the video card in that same machine was a low-cost add-in and it shows, with Graphics and Gaming Graphics scores of 3.9 and 3.7, respectively. That last number is the one that appears in big bold type in the Welcome Center.

Windows Experience Index

No, you can't score a perfect 10 yet. The top rating is 5.9. But maybe someday:

Over time, we expect to introduce higher scale levels of 6 and beyond. This will be done approximately every 12-18 months, as new innovations in hardware become available. When new base scores are introduced, existing scores will not change (i.e. a PC with a base scored of 2.2 today will score a 2.2 in the new updated index, unless its components are upgraded).

In this thread at, a group of Vista beta users have been posting details of their Experience Index scores. An NVidia GeForce 7900 GT/GTO with 527MB of graphics memory earned perfect video scores in, while a similar NVidia GeForce 7900 GS and a Radeon X1900 with more than 1GB of graphics RAM both earned a perfect 5.9 for Graphics and a so-close-but-not-quite 5.8 rating for Gaming Graphics.

An Intel Core 2 6600 CPU at 2.4GHz gets a 5.8; an older 3.2GHz Pentium 4 earns a 4.3. My SATA-300 controller with a 7200RPM hard drive and large cache gets a 5.5. If you're interested in learning how to pick components that will get a perfect score, this thread is worth scrolling through.

If you have any Windows Vista questions,click the e-mail link on my bio page and send them to me. I can't promise to reply personally or on this site, but I do read every one. Be sure to include your e-mail address (I won't share it with anyone and won't use it for anything except to contact you with answers or questions of my own.)