Windows Experience Index: An In-Depth Look

Windows Experience Index:   An In-Depth Look

Introduction

The Windows^® Experience Index is a new feature built into Windows Vista™. It is designed to help consumers understand how well Windows Vista and the software running on it will perform on a specific PC. The index achieves this by assessing the performance of the PC and assigning a score to it. The higher the score, the better the PC will perform.

The overall PC performance is represented by the base score. The base score is derived from 5 sub-scores for each of the following 5 attributes:

The Windows Experience Index is useful for the following:

1. When buying a new PC, it is useful for determining the quality of the Windows experience a buyer can expect from a particular PC.

2. When upgrading a PC, the index is useful for estimating the overall improvement a PC user can expect to get when replacing or adding a new hardware component.

3. When buying software, the software package may include the recommended Windows Experience Index base score a PC should have in order to run the particular software application well. If a PC has that score or a higher one, the software will run well on it.

About this document:

This document describes the Windows Experience Index (WEI) Model, what it is useful for, how the scores are computed, and how consumers can use it.

The Scale of the Index

The scale of the Windows Experience Index ranges from 1 to 5.9. The higher the score for a particular performance area, the better performance you can expect from that area.

The scale is useful when comparing hardware components and when comparing whole PCs. The scale was created so that a full score point of improvement usually means significant additional capabilities in the particular sub area, while a better fractional score means an incremental improvement. The integer number of a base score is referred to as the Windows Experience Index base score level. For example a PC with a Windows Experience Index base score of 5.3 is considered a level 5 PC.

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).

Base score definitions

Each base score level defines an improved experience over lower levels. A PC will work well running scenarios of its level in addition to scenarios of lower levels.
The base score levels at a glance:

* Level 6 - Will be defined when new hardware innovations reach the market.

The following are detailed descriptions of each of the base score levels:

Computing the base score

The Windows Experience Index score – often called the base score – is always a decimal value greater than zero. E.g. the base score is a number like 3.6 or 5.6.

Since a system’s performance is limited by its slowest component, the final system base score is the lowest value of the five sub-scores. In the example below, the WEI base score is 3.8 and is determined by the processor’s score of 3.8.

Note: The model logic is tolerant of one sub-score being below the threshold for a particular level by 0.1. For example, assume that in the above example, the memory score was 4.0 and the processor score 3.9. This would mean that the processor score would very marginally be the only item keeping the base score below level 4. The model addresses this issue by rounding up a single value that is below the next round level by 0.1.

Computing each sub-score

Each sub score in the index was created to measure the performance of a critical piece of hardware. The scores are calculated by measuring one or more relevant performance attributes, and then converting the values (normalizing) to a score between 1.0 and 5.9.

In this section you can read what is tested for each sub-score.

The CPU Score

The CPU score was created to measure the processor performance when tasked with common Windows usage activities. The processor is assessed on the following items:

1. Compression and decompression using the LZW compression algorithm.

2. Compression and decompression using the Windows Vista compression algorithm used for hibernation files, ReadyBoost and other features.

3. Encryption and decryption assessment

4. Computing hashes

5. Encoding of video

The results are normalized and weight averaged in order to arrive at the final CPU sub-score.

The Memory Score

The memory score measures the bandwidth of moving data into and out of memory in mega bytes per second. The higher the bandwidth, the better the memory.

Not having enough memory is a limiting factor on performance. As a result, the amount of memory in the system constrains the score value. The amount of system memory is determined by the overall system memory minus any memory reserved for graphics (if any).

The amount of memory limits are:

The Graphics Score

This score is intended to reflect how a system will run Aero (desktop composition) and playback Windows Media Video. It measures video memory bandwidth (in mega bytes per second) and converts it to a score between 1.0 and 5.9.

If the system does not support DirectX 9 (DX9) graphics, than the system receives a graphics score of 1.0 regardless of driver type. If the system supports DX9, but does not have a WDDM Driver (Windows Vista Display Driver Model) than the system can receive a graphics score of 1.9 at the most.

The Gaming Score

The gaming score measures the frames per second the graphics card can handle for various textures.

Additional notes:

· If the graphics card does not support D3D 9 then it receives a Gaming score of 1.0.

· If D3D 9 is supported, the card is DX9 capable and has a WDDM driver, it will score at least 2.0.

· If the score is greater than or equal to 5.0 and the graphics sub-system does not support Pixel Shader 3.0 then the score is limited to 4.9

The Disk Score

The disk score measures disk bandwidth (in mega bytes per second). The conversion to an index number is set up in a way that all modern disks will score at least 2.0.

Using the Windows Experience Index

The Windows Experience Index is very useful for consumers when buying a new PC, when upgrading an existing PC and when buying new software. This section explains how the index can be used in each of these situations.

When buying a new PC

When buying a new PC a customer is usually confronted with the dilemma of which PC to choose. A PC’s value is multi-dimensional. The value is a collection of many attributes including performance, industrial design, noise, size, weight, power consumption, battery life, connectors, capacity of disk & memory, peripherals (DVD burner, etc.), networking, included software, and more. The most difficult aspect to understand is how well the PC will perform when running Windows and other software and the type of experience you can expect. The only way to do this today is to look at a long and arcane list of technical terms and to try to figure out what the combination of them would mean when running Windows. This is very difficult to do, even for the most experienced customers.

This is where the Windows Experience Index comes in. It can help you while shopping for a new PC:

1. First, determine the base score level of PC you are looking for. This can be done using the “base score levels table” on page 3.

2. Second, look for PCs with that base score level or higher. For example, if you determined you need a PC with a base score of 3.0, look for PCs at level 3.0 and above.

3. To determine which PC to buy, look at all the additional characteristics each PC provides and determine which package if the right one for you.

4. To compare the experience you can expect to get from 2 different PCs, you can check their WEI base scores as well as their sub-scores for each of the five areas. Let’s look at some examples of how this can be done.

Example A:
(differences are marked in bold)

Example A shows 2 similar PCs. PC 2 is the same as PC 1 but with the following additions: it has a better graphics card as well as wireless Ethernet built in, and it is expandable to double the memory. It gets a slightly better WEI score due to the improved graphics capabilities it has. It also costs $90 more.

In this case, the WEI score helps the consumer understand the differences between the 2 PCs and make up their mind on which of the PCs to buy. The decision is about buying PC1 or buying PC2 for $90 more and getting better graphics, wireless connectivity and a higher memory limit.

Example B:
(differences are marked in bold)

Example B shows 2 PCs with the same WEI base score. The WEI base score is the same due to the lowest sub-score of 4.1 for the primary hard disk. Even though PC 4 has dual hard drives in a RAID 1 configuration, the primary disk read/write bandwidth is the same, and as a result they both get the same sub-score. PC 4 also has faster memory and more of it (2Gb instead of 1Gb). This is captured in the better memory score for PC 4, but since the lowest sub-score for the hard disk is the same for both, they both get a final base score of 4.1.

Even though both PCs get the same score, the differences are noticeable and are quite easy for a customer to understand. PC 4 costs $334 more than PC 3. It has faster memory and more of it. It also has 2 hard drives in a RAID 1 configuration which helps protect data against failure.

When upgrading a PC

The WEI score is very useful when upgrading a PC. The following examples illustrate how the WEI score can be used when considering an upgrade.

Ordering upgrades directly from the PC manufacturer

Rachel, a PC user decides to upgrade her PC after starting to view videos and editing photos on it. She goes into “Performance Information and Tools” from the control panel. Her system rating shows a WEI base score of 2.1.

On the bottom, next to the logo of the PC manufacturer, Fabrikam, she notices the following link: “View ways to increase your rating”. After clicking it, she is directed to the Fabrikam web site which suggests a few upgrade options for her. She chooses the components she is interested in and is given directions for a self upgrade or for sending her PC in for the upgrade.

See web site screen shot below.

Manually upgrading a PC

Memory example

Consider a customer who owns the following PC:

The customer has recently bought a digital camera and is now using the PC with many more programs running concurrently. Due to the added load on the PC, the customer feels the PC is less responsive than it used to be. He thus goes into “Performance Information and Tools” in the control panel to try to discern how to improve the PC performance. Looking at the WEI results presented there, it is clear that the base score of the PC is significantly impacted by the memory score which is by far the lowest score. To improve performance, it thus seems that adding more memory or putting in faster memory if possible would be the method of choice for improving performance. Checking the amount of memory in the PC by clicking on the “View and print details”, the customer discovers that the PC has only 512MB of RAM available. This indicates that the low memory score is probably due to lack of memory. The conclusion would be to check if the PC can support more memory and upgrade it.

Graphics example

Consider this second PC:

This customer has recently bought a new game. The game works well on this PC but is throttled back due to lack of performance by the PC. The customer decides to take a look at the WEI score by going into “Performance Information and Tools” in the control panel. Looking at the scores, it is apparent that this PC could benefit from an upgrade of the graphics card. The customer walks into a computer retail store and looks for a graphics card with a manufacture recommended component sub-score of 5.0 or higher on it. The customer ends up buying a Fabrikam nPower series graphics card and upgrading his/her PC. After the upgrade, the new game graphics are smoother and have additional lighting effects. When looking at the WEI scores after the upgrade, the customer notices the new PC score has changed from 3.0 to 5.1. The new score is the following:

The new base score is now determined by the primary hard disk sub-score, which is now the lowest of the sub-scores.

When buying software

When buying software, knowing your PC base score is very useful. With it you can determine if the software you are buying will run well on your PC. Microsoft is working with software vendors to use the base score and sub-scores for recommended system requirements. We expect to have some software vendors using it at the time of Windows Vista launch and many more following the launch.

When determining if your PC can run a specific software package, look for the system requirements section on the retail product packaging. The recommended WEI score is the base score the software vendor recommends your PC should have to get an adequate experience when running this software application. The packaging may also include a minimum WEI base score which would indicate the minimum performance a PC should have to be able to run the application.

Example:

Summary

The Windows^® Experience Index is a new feature built into Windows Vista™. It can considerably help consumers understand how well Windows Vista will perform on a specific PC, and make the buying process of new PCs, hardware upgrades and software simpler.

The following topics about the Windows^® Experience Index were covered in this document:

1. Description of the Windows Experience Index

2. How the scores are calculated

3. How the index can be used in the following cases:

a. When buying a new PC

b. When upgrading a PC

c. When buying software