Plenty of people will bring up the Pentium FDIV bug here, but the reason we didn’t include it is simple: Despite being an enormous marketing failure for Intel and a huge expense, the actual bug was tiny. It impacted no one who wasn’t already doing scientific computing and the scale and scope of the problem in technical terms was never estimated to be much of anything. The incident is recalled today more for the disastrous way Intel handled it than for any overarching problem in the Pentium microarchitecture.
We also include a few dishonorable mentions. These chips may not be the worst of the worst, but they ran into serious problems or failed to address key market segments. With that, here’s our list of the worst CPUs ever made.