I got my first computer in 1981, when I was still at Bell Labs. A Zenith, as I recall, running CP/M 80. There was a C-like compiler, but it was a subset. I think that computer had a z80 chip, so it wasn't an x86.
Then I got an IBM PC in 1982, with an 8088 (16-bit word, 8-bit bus), and I'm pretty sure the first real C compiler was Lattice C. Microsoft picked it up and called it Microsoft C. Then, maybe a couple of years later, they came out with their own C compiler, written in-house, I think. (As I recall, I got my Lattice C compiler, which was very expensive, for free for writing a review for BYTE Magazine, but I can't find the review in my office or online, so maybe I'm imagining that. Or maybe I never finished the review or they didn't print it.)
I had an early Macintosh, too, and used Lightspeed C. I think it was essentially complete C. It was a whole IDE, incredibly fast, and I used it for commercial applications for the Mac. I continued to use that until Apple bought Next and revised their product line to use NextStep. Then I used what Apple had, but it was Objective-C (blend of Smalltalk and C) which is what you wrote NextStep apps in. I think we used Objective-C for Mac work until the early 1990s, when I stopped writing native Mac apps.
Lots of missing details here, I'm sure.
The August 1983 issue of BYTE Magazine was all about C, and has three articles reviewing C compilers for CP/M 86, the IBM PC, and CP/M 80. There's also an article called "The C Language and Models for Systems Programming" by two guys who know about that stuff, Stephen C. Johnson and Brian W. Kernighan. Here's a link to the issue:
https://archive.org/details/byte-magazine-1983-08
Marc