If you just arrived from 2016—possibly in a modified DeLorean—you’re probably wondering why you hear the term Semi-Annual Channel (SAC) across Microsoft’s major product lineup (Windows 10, Office 365 Pro Plus, Windows Server, and System Center). You may also be questioning where familiar terms—such as Current Branch (CB) and Current Branch of Business (CBB)—have gone, and if all of this was part of Microsoft’s grand scheme. The following is an investigation—through a series of announcements that Microsoft has made since Spring 2017—to help you understand how the Semi-Annual Channel came to be and its present state.
It all started with the Windows 10 as a Service model that Microsoft introduced soon after the release of Windows 10. In a nutshell, what Windows as a Service means is that Microsoft will not be releasing a new Windows title like they used to do (Windows XP to Windows Vista to Windows 7 to Windows 8.1). Instead, they will only release periodic updates.
The deployment model is simple. Security updates are delivered to customers every month, invariably across all the branches. For feature updates, there were traditionally two branches. Customers who were supposed to update to the latest feature release as soon as it is released fall under CB. Businesses that wanted to wait for four more months to install the update were under CBB. The option to delay the update for another four months is the only difference between CB and CBB. How do you become eligible for CBB? You need Windows 10 Enterprise with Software Assurance.
And don’t worry, I did not forget LTSB. We’ll talk about that at the end!
The History of SAC
Right around the spring of 2017, after the release of Windows 10 Update 1703 (also known as the Spring Creators Update), Microsoft made a big announcement that Windows was committing to a predictable, twice-per-year feature release schedule, targeting September and March of each year. In the blog post, Microsoft said that they are doing this to align the servicing models for Windows 10, Office 365 Pro Plus, and System Center Configuration Manager for customers—particularly those with Secure Productive Enterprise (now rebranded as Microsoft 365). The same day, on the Office 365 Pro Plus blog, Microsoft announced that they were reducing the Office 365 Pro Plus update cadence from three to two times a year, with semi-annual feature updates to Windows 10 and Office 365 Pro Plus targeted for March and September. The concept of “Semi-Annual” was informally used for the first time in that announcement. A few months later, Microsoft formally introduced Semi-Annual Channel in a blog post. At that time, Microsoft also announced that Semi-Annual Channel had replaced CB and CBB.
Under the new Semi-Annual Channel for Windows 10, the difference between the functional equivalents of CB and CBB was at first vague. But, along with the full availability of Windows 10 Fall Creators Update (1709), Microsoft clarified that CB would be translated to Semi-Annual Channel (Targeted). This is what all home users and most small-business corporate pro users get. CBB translated into a choice to manually defer the update until Microsoft announced the full availability (which is within four months).
Now you know why Semi-Annual Channel gets nuanced under the Windows 10 realm. But, the story doesn’t end there—as you’ll soon read.
Extending Semi-Annual Channel Beyond Windows 10
In June 2017, Microsoft announced that Windows Server was joining the Semi-Annual Channel (SAC) cadence to deliver updates at a faster pace. In October 2017, right around the time Windows 10 Fall Creators Update was released, Windows Server made their first Semi-Annual Channel version (1709) available to customers.
The difference between Windows 10 SAC and Windows Server SAC is an important thing to note here. Unlike Windows 10, Windows Server Semi-Annual Channel releases are not an update to the existing OS. Instead, it is more of a fresh install. For instance, if you want to move from SAC version 1709 to 1803, you will have to run a clean install of 1803. Earlier in the blog, I mentioned that Microsoft committed to the alignment of service models for Windows 10, Office 365 Pro Plus, and System. On February 8, 2018, Microsoft announced (and later made) the first Semi-Annual Channel version of System Center (1801) available.
It is important to note that even though SAC is the general terminology used for updates and version releases across the various products categories, there are differences in the support policies. For example, Office 365 Pro Plus SAC update is only supported for 14 months, while Windows 10, Windows Server, and System Center SAC releases are generally supported for 18 months.
Also, Microsoft announced six more months of Support Extension for the last four Feature Updates of Windows 10. Worth noting is that Microsoft also runs a Long-Term Servicing Channel (LTSC)—formerly known as Long Term Servicing Branch, or LTSB—for Windows 10, Windows Server, and System Center. An LTSC release happens every three years or so, and it comes with five years of regular support plus five additional years of extended support. You can read more about the extension here.
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