Under the Hood, Windows 7 Is Vista's Twin

At Microsoft's recent Professional Developers Conference (PDC) in Los Angeles, the air crackled with anticipation. On the heels of Vista, arguably the biggest disaster in Microsoft's history, Windows 7 was about to be revealed. A blast of fanfare, and Chief Software Architect Ray Ozzie took the stage to pull the wraps off the new desktop operating system--which would deliver better performance, an improved user experience, and some nifty media-sharing features. The crowd salivated at the chance to play with Microsoft's latest and greatest.

Note: For a look at some of PC World's Windows 7 coverage to date, see:

As Windows desktop blogger for InfoWorld (a sister publication of PC World), I was drooling, too. When I got my hands on the Windows 7 "pre-beta," distributed right there at the show, I immediately installed it and began running tests. For PC World, I did an analysis of the changes (or lack of them) that consumers might see. For a deeper dive into my Windows 7 tests, check out Windows 7 unmasked on the InfoWorld site. The more I dug into Windows 7, the more I became convinced that I was dealing with an OS that was a slightly tweaked, nearly baked revision of Windows Vista.

If any pre-beta software ever called for a close look and benchmark testing, Windows 7 was it. 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 behavior 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.

Bottom line: So far, Windows 7 looks, behaves, and performs almost exactly like Windows Vista. And it breaks all sorts of things that used to work just fine under Vista. In other words, Microsoft's follow-up to its most unpopular OS release since Windows Me threatens to deliver zero measurable performance benefits while introducing new and potentially crippling compatibility issues.

[Will your PC run Windows 7? Find out with InfoWorld's Windows 7 compatibility calculator.]

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 InfoWorld's free Windows Sentinel tool.

The View From Inside

Here's what I found in the heart of the OS. 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.

[What's so wrong with Vista, anyway? See "Death match: Windows Vista versus XP."]

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.

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'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.

(See all of InfoWorld's coverage and analysis of the Windows 7 prerelease in our special report. )

Benchmarking Windows 7

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.

I ran a complete battery of tests, through which I simulated a complex, multiprocess workload under Windows 7 consisting of client/server database, workflow, and streaming media playback tasks. All tests were conducted on a 2GB Core 2 Duo (T7200) laptop PC (the Dell XPS M1710) configured to dual-boot between Windows 7 Ultimate M3 and Windows Vista Ultimate SP1.

[For all the nitty-gritty details on my Windows 7 tests, check out Windows 7 unmasked on the InfoWorld site.]

You'll find the complete details in my InfoWorld article, but in a nutshell, Windows 7--the build of Windows 7 that I tested was dubbed M3--is a virtual twin of Vista when it comes to performance. The few minor variations I observed during comparative testing are easily explained away by slight tweaks to the kernel (such as the aforementioned MDAC changes); they certainly don't indicate a significant performance overhaul. More important, these variations pale in comparison with the 40 percent gap in performance I've observed between Vista and Windows XP SP3. From a raw throughput perspective, Windows 7 promises to perform as poorly as its predecessor. "Pre-beta" notwithstanding, the reality is that any hope for closing of the performance gap with Windows XP is unlikely to materialize in Windows 7.

Potential Pitfalls: Compatibility Woes Continue

One of the more surprising results of my early Windows 7 testing was the number of unexpected compatibility issues. For example, Skype 3.8 would randomly crash without warning. But the worst compatibility issue was with VMware Workstation 6.5.

After installing VMware Workstation on the Dell M6400, I was unable to launch any virtual machines. I eventually worked around the problem, but the fix came at a price: the loss of drag and drop between Windows 7 and the VMware guest OS. Nor was this the only issue I encountered with VMware Workstation.

[For more about Windows 7's compatibility problems, check out the expanded version of this article.]

Just how many Vista-compatible applications will break in this manner is anybody's guess. But I'm genuinely concerned. If Windows 7 really is Vista at its core--as the close similarity of their System process, memory, and performance profiles suggests--then the fact that Microsoft has still managed to break applications as popular as Skype is disconcerting. At the very least, it doesn't bode well for Microsoft's promises to make the Vista-to-Windows 7 transition truly seamless.

[If Windows 7 is a dead end, what's next? Several new personal computing paradigms are emerging.]

Lipstick on the Pig

So where does this leave us? For starters, we can now say with some certainty that the Windows 7 build I tested is just a repackaging of Windows Vista. Key processes look and work much like they do under Vista, and preliminary benchmark testing shows that Windows 7 performs right on a par with its predecessor. Frankly, Windows 7 is Vista, at least under the hood; if nothing else, this should translate into excellent backward compatibility with Vista-certified applications and drivers.

Except that it might not. The M3 build of Windows 7 breaks all sorts of things that, frankly, it shouldn't be breaking. Worse still, the suspected source of a major compatibility bump--the neutered UAC prompts--is in fact architectural in nature, one of the few truly new features of Windows 7's secure computing stack.

Windows Vista has permanently eroded the company's reputation among IT decision makers, and from what we've seen of Windows 7 so far, Microsoft still doesn't get it.

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