Screenshot by Lance Whitney/CNET

They said they'd do it by the end of August. And as we head into the last stretch, it seems Microsoft has released to manufacturing (RTMed) Windows 8.1, its next release of Windows.

Windows SuperSite editor Paul Thurrott tweeted on August 23 that Windows 8.1 had RTM'd. Thurrott said the final RTM build number is 9600.16384.130821-1623.

I talked to another contact of mine who said the internal RTM e-mail made the rounds inside the Windows division on August 23. A third source close to the company confirmed Microsoft RTM'd Windows 8.1 on August 23, and announced internally that the quality metrics for Windows 8.1 were back in line with those of Windows 7. (The vast amount of changes in the Windows 8 code base resulted in an increased number of crashes and hangs for Windows 8, one of my contacts explained.)

I asked a Microsoft spokesperson if Windows 8.1 RTM'd on August 23 and was told the company had no comment.

Microsoft may have opted against announcing Windows 8.1's RTM on Friday so that the news wouldn't be overshadowed by the announcement that CEO Steve Ballmer is retiring some time within the next 12 months. As I blogged previously, my sources said Microsoft was targeting Monday August 26 as the day it would RTM Windows 8.1.

In June, officials said that Microsoft would be providing the final RTM bits to OEMs before the end of August.

The real question on some developers', IT pros', and other users' minds is whether Microsoft will make the RTM bits available to anyone early. In other words, will TechNet and MSDN subscribers get the Windows 8.1 gold bits in the next couple weeks or so, as Microsoft has done traditionally?

As I've noted previously, my sources said that Microsoft's game plan is to withhold the Windows 8.1 RTM bits until launch this year, which means almost no one outside (other than OEMs) would get officially released Windows 8.1 bits until October 18.

Microsoft may reverse that decision, but on the server side of the house, officials admitted that the Windows Server 2012 R2, System Center 2012 R2 and Windows Intune Wave E offerings won't go to anyone in final form before October 18.

Windows 8.1, codenamed "Blue," is introducing a number of changes designed to make the new operating system more palatable to current Windows users. Windows 8.1 is adding a Start Button, a boot-straight-to-desktop option; the ability to unpin all Metro apps; built-in tutorials; an improved Windows Store and a host of other consumer- and business-focused features. Microsoft launched its one and only Windows 8.1 consumer preview test build in late June.

This story originally appeared as "Microsoft releases to manufacturing Windows 8.1: Sources" on ZDNet.