Microsoft is buying Activision Blizzard for $68 billion—the biggest deal in the software giant’s history—in large part to help it supercharge a Microsoft subscription game service that could shake up how people pay for console games. That service has a long way to go before it transforms Microsoft’s games business, though.

In recent years, the revenue growth rate from Microsoft’s Xbox games and services business has fluctuated wildly. That’s occurred even as that business—which includes everything from the sales of Microsoft’s own games to royalties from the sale of third-party Xbox games to fees from Game Pass, the company’s Netflix-like game service—hit a high of $3.8 billion in the holiday quarter, our analysis of Microsoft’s securities filings shows (the figure excludes sales of hardware, including the company’s Xbox consoles).

This pattern repeats a feast-or-famine cycle common in the game console business, which is highly sensitive to the release of new hardware and hit games. And it underscores just how much Microsoft needs the Activision deal to make Game Pass into a steady source of recurring revenue alongside its traditional game software sales.