Under the Hood, Windows 7 Is Vista's Twin

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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.

This story, "Under the Hood, Windows 7 Is Vista's Twin" was originally published by InfoWorld.

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