Comment by canucker2016

SLM (aka slime, shared file-system source code control system) was used in most of MS, aka systems & apps.

NT created (well not NT itself, IIRC, there was some an MS-internal developer tools group in charge)/moved to source depot since a shared file-system doesn't scale well to thousands of users. Especially if some file gets locked and you DoS the whole division.

Source depot became the SCCS of choice (outside of Dev Division).

Then git took over, and MS had to scale git to NT-size scale, and upstream many of the changes to git mainline.

Raymond Chen has a blog that mentions much of this - https://devblogs.microsoft.com/oldnewthing/20180122-00/?p=97...