For me the interesting alternate reality is where CPUs got stuck in the 200-400mhz range for speed, but somehow continued to become more efficient.
It’s kind of the ideal combination in some ways. It’s fast enough to competently run a nice desktop GUI, but not so fast that you can get overly fancy with it. Eventually you’d end up OSes that look like highly refined versions of System 7.6/Mac OS 8 or Windows 2000, which sounds lovely.
Given enough power and space efficiency you would start putting multiple cpus together for specialized tasks. Distributed computing could have looked differently