After months of speculation, Windows 7 was finally unveiled last month at Microsoft's Professional Developers Conference (PDC). Through a series of well-orchestrated keynote presentations and supporting breakout sessions, Microsoft walked conference attendees through the highlights of its new desktop OS: better performance, an improved user experience, and some nifty media-sharing features. Overall, Microsoft's pitch was quite compelling, and the PDC crowd was practically salivating at the chance to play with Microsoft's latest and greatest.

But after the stage props came down, and after the projectors finally went cold, attendees were left with a pre-beta copy of something that looked less like a new OS than the repackaging of an old one. At least that was my impression after I started exploring the Windows 7 M3 (Milestone 3) bits that came on my shiny new 160GB Western Digital USB hard disk (one of the better tchotchkes I've received at a conference). And the more I dug into Windows 7, the more I saw an OS that looked and felt like a slightly tweaked version of Windows Vista.

Just what was so new about Microsoft's next Windows, apart from a rejuggled UI? Windows 7 appeared to suck memory like Vista, to consume CPU like Vista, and to have the same consumer focus. How would this product be received by business customers, the vast majority of whom had soundly rejected its predecessor? After all, if Vista wasn't good enough for business, then surely a Vista-derived encore would meet with a similarly chilly reception.

If any pre-beta software ever called for a close look and benchmark testing, Windows 7 M3 was it. With so many questions to answer, and the fate of Windows in the enterprise hanging in the balance, I rolled up my sleeves and dove in. I started by examining Windows 7's innards -- the kernel and other low-level structures -- then slowly worked my way out to subsystem behaviour and application runtime characteristics. Because one of the focal points of Microsoft's keynote presentation was improved performance, I looked for signs that Windows 7 would be faster, more responsive, and less resource-intensive than the bloated Windows Vista.

Note: All the test tools I used for this article are freely available from the exo.performance.network Web site. You can also test your current PC for Windows 7 compatibility now, and then monitor Windows 7 performance on your own system when it enters public beta later this year, using our sister magazine InfoWorld's free Windows Sentinel tool.

The view from inside: a minor tweak to Vista

As I mentioned in the intro, I began my exploration of Windows 7 by poking around the OS's innards. Using a combination of the Windows Performance Monitor utility and some reference data I'd gathered from Windows Vista and XP, I began comparing the runtime structure and composition of various OS processes and services.

First up was the Windows 7 kernel -- aka the System process. When comparing Windows versions, it's always good to start with the kernel because this is where the most fundamental changes take place. For example, when Microsoft went from Windows 2000 to Windows XP, the System process gained 21 execution threads in its default configuration. Likewise, when Microsoft introduced Windows Vista, the kernel gained 39 execution threads.

In fact, the kernel in each major new version of the Windows OS has spawned a different, typically higher number of threads. So when I examined Windows 7 and found a nearly identical thread count (97 to 100) for the System process, I knew right away that I was dealing with a minor point-type of release, as opposed to a major update or rewrite. This was not "MinWin," the mythical, streamlined new Windows kernel that promised a clean break with the bloated Vista.

Next up: the memory footprint for the kernel. Like the System process, memory footprint tends to vary widely from version to version, with successive releases showing an ever-expanding kernel working set. Based on the thread count values I observed in my previous example, I anticipated that the working set would be similar to Vista's. And in keeping with my initial suspicions, Windows 7 M3's System process indeed consumed a similar amount of memory (3.5MB to 4.5MB). So far, the new OS was looking a lot like Vista.

In fact, as I worked my way through the process lists of the two operating systems, I was struck by the extent of the similarities. Key subsystems, including the Desktop Window Manager (dwm) and Client/Server Runtime (csrss), sported similar thread counts and working set sizes. When viewed side by side in Performance Monitor, Vista and Windows 7 were virtually indistinguishable.

Two of Microsoft's selling points for Windows 7 have been improved performance and lower resource requirements when compared to Vista. However, these sorts of gains traditionally have been difficult to realize without significantly modifying the OS at a kernel level, and the telltale signs were showing that the changes were minor. What would happen if I threw some test workloads at this OS?