Microsoft Explains Vista Build Numbers

The Microsoft official responsible for releasing Windows Vista builds explained in an interview published on the Vista Team Weblog this week some of the intricacies of how the build numbering scheme for Release Candidates works.

In the interview, Sven Hallauer, director of release management for Windows Vista, said the company currently has parallel build cycles in play for builds numbered 5400 through 5699 which are reserved for Release Candidates (RC). At the same time, it also has reserved builds numbered 5700 and above for Release to Manufacturing (RTM) -- the step following the last RC build and the code that will ultimately be released to customers.

"So does this mean that MS is working on builds for RC1 and RTM in parallel? You bet!" says the posting that accompanies the interview online.

"We've done this since XP...basically, it helps us to optimize the ability to make the code move forward in a very fast way," Hallauer said. "That's something that we do at the end of every major milestone...that we basically branch off [to one of the sets of build numbers], and out of the branch we drive the actual milestone build."

The interview is posted in both .MP3 and Windows Media Audio (.WMA) formats.

The new code branches appear to be yet another indication that Microsoft is determined to stay on track to release Vista to business customers in November and release to consumers in January. Earlier this week, the company made 100,000 pre-Release Candidate 1 copies of an interim release build available for download.

The pre-RC1 builds followed disclosure earlier in August that the company had started a Release Candidate "branch" in Vista’s code tree. The company typically releases from one to three RCs before releasing the final code to manufacturing.

"We've got about 5,000 engineers working on [Vista]...and when you get close to the end of the milestone...the last five, maybe six weeks, there comes the point where you say, 'We need to slow down the churn in order to bring everything together' [and] saying, 'Hey, we can stabilize this platform at a certain quality bar and then go ship it.'" Counting other parties, such as product marketing, the total team is more like 8,000, he said -- a far cry from the early days of MS-DOS and Windows when there were only small teams working to turn out the code for major products.

The biggest risk, Hallauer said, is in regression testing of any software product, and the build numbering and branching scheme is a method to help resolve outstanding fixes. "All the fixes taken into the branch out of which we ship the major milestones always come back to the main line [of the code tree] so they're always part of what we ship as the next milestone out."

Right now, of course, the development teams are putting in 50- and 60-hour weeks. But Release Candidate 1 (aka "RC1") will define how close the company actually is to Release to Manufacturing, or RTM. And as soon as RC1 comes out, Hallauer is urging everyone to aggressively begin testing it right away in order to be sure that any major problems are found and fixed.

"Time is of the essence...we've got a feedback window of about two or three weeks after RC1 is released where we can really make changes that are deeper into the product code base...and thereafter we just become very, very constrained in terms of what we actually can change without resetting the clock and slipping the release [date]."

In terms of current status, whereas in the early beta stages, testers identified bugs in the core code, these days most bugs are being found in third-party driver code, Hallauer said. Although the company has not said yet when RC1 will be released, many analysts anticipate that it will ship by mid-September.

You can listen to the entire interview here.

About the Author

Stuart J. Johnston has covered technology, especially Microsoft, since February 1988 for InfoWorld, Computerworld, Information Week, and PC World, as well as for Enterprise Developer, XML & Web Services, and .NET magazines.


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