Yes - thus "MS's fortunes" is also tied to AMD.

> but they've traditionally been a much smaller outfit

Tradition isn't really the key here. Intel does explore more markets and holds much more market share (specifically desktop and laptop PCs) right now. AMD has been steadily growing in the desktop/laptop space, aside from their semi-custom (console) business, and they have made meaningful strides in performance and efficiency that at least keep Windows (and thus Microsoft) in the game now that Apple Silicon M1 has brought Macs to the table as competitive performers.

But - I'm less convinced Microsoft has to copy Apple and design efficient ARM chips in-house in order to remain competitive, at least in the PC business. I think we'll see some shifts in market share from Windows to MacOS, initially in laptops, and the rest will remain to be seen, but Apple should certainly become competitive in other PC areas as they roll out their new lines of CPUs. There are plenty of areas where AMD's performance CPUs remain very competitive, and Windows is still the preferred "mainstream" and "gamer" platform.