Inside CNET Labs: Windows Vista SP1 performance

The long-awaited Service Pack 1 update for Windows Vista brings with it a number of significant bug fixes and other improvements. Microsoft says that with it you will also see a number of noticeable performance improvements as well. In our initial round of testing, we saw a mixed bag of results: we saw a few notable performance improvements under some conditions as well as significant performance degradations in others. For the most part, however, we saw little difference in performance between Vista and the Vista SP1 update.

As we dug a little deeper into Microsoft's claims, we discovered that many of the performance improvements being touted aren't actually directly attributable to SP1. Many of the claimed performance improvements, such as improved boot-time, are actually more a function of improved third-party drivers and applications that are benefiting from a year's worth of programming for Vista, and from the programmers getting continued feedback and guidance from Microsoft. As long as you have been diligent about keeping your Vista system current with the latest Windows updates and third-party drivers, you likely already have many of the potentially performance improving enhancements.

That's not to say that there aren't any potential performance benefits in SP1. An area of Vista the Microsoft developers spent a great deal of time trying to improve was file copying. Under some scenarios, copying files with Vista took longer than with XP. Under other scenarios, Vista, gave the impression that Vista was taking longer to copy files than XP, by not dismissing the copy dialog box sooner. Much of this has to do with the mode in which these file copies are taking place. XP uses a cached I/O mode; Vista uses a predominantly un-cached I/O mode; and Vista SP1 is back to almost always using a cached I/O mode for file transfers. (For an in-depth, under-the-hood discussion of all this, see Microsoft employee Mark Russinovich's blog entry titled Inside Vista SP1 File Copy Improvements. Among other things, Mark is credited with discovering the rootkit on Sony BMG audio CDs in 2005.)

In our file copy tests of approximately 1GB worth of files of varying size, we saw noticeable performance improvements with Vista SP1 over Vista in several scenarios. Scenarios such as copying a folder from one location to another on the same disk, or when copying a folder from one internal drive to another.

The one area where we saw a significant performance degradation with SP1 was when writing the folder to a USB 2.0 hard drive. We saw between a 44- and 54-percent degradation on Vista SP1 versus Vista. It's difficult say exactly what is causing this performance drop. In Mark Russinovich's blog, he mentions a number of scenarios where Vista SP1's file transfer performance can be potentially slower than with Vista. While this particular scenario was not one of the ones he outlined, it is possible that the same factors apply. We will continue to investigate this issue and will report back with any new findings.

For the most part, we have not seen significant performance difference between Vista and Vista SP1 in terms of application performance, boot time, shutdown time, and laptop battery life. In our initial round of testing with a Dell XPS M1530 laptop, we did see a significant improvement with Adobe Photoshop CS3 performance, which we initially speculated was because of the reintroduction of cached I/O into SP1. However, we have not been able to recreate this performance boost on other systems. We are still looking into this issue as well.

So does Vista SP1 deliver all the performance benefits it promises? So far the answer is both yes and no. We didn't look at every claim Microsoft is making about SP1's performance improvements--for instance, Microsoft says that you should also see significant performance improvements with many types of network file transfers. However, At the end of the day, updating your system to SP1 is not really about the performance improvements--it's primarily about having a more bug-free, stable operating system. Of course, having a better performing operating system is always a plus.

For more about Windows Vista, see CNET's Windows Vista resource guide.

Find out more about how we test laptops and desktops.

System configurations:

CNET Labs testbed desktop system
2.2GHz AMD Phenon 9500; 2048MB DDR2 SDRAM 800MHz; 512MB ATI Radeon HD2900XT; 74GB Western Digital 10,000rpm; 250GB Maxtor 7,200rpm
Dell XPS M1530
2.4GHz Intel Core 2 Duo T7700; 2048MB DDR2 SDRAM 667MHz; 256MB Nvidia Geforce 8600M GT; 160GB Hitachi 5,400rpm