If Intel ships a CPU with a bug in it then that is an expensive mistake. If they produce a bunch of CPUs with a bug (escape to silicon) that can also be an expensive mistake.
That said:
1) I deal with CPU bugs pretty regularly on Chrome. Some old CPUs behave unreliably with certain sequences of instructions and we get bursts of crashes on these CPUs with some Chrome versions.
2) Intel regularly "fixes" CPU bugs with microcode updates.
3) The Spectre family of vulnerabilities are arguably CPU bugs.
4) The Pentium fdiv bug was definitely a CPU bug.
So, CPU bugs escape to silicon all the time. Way more than I would have guessed just a few years ago. Our industry is built on a pile of wobbly sand.
If Intel ships a CPU with a bug in it then that is an expensive mistake. If they produce a bunch of CPUs with a bug (escape to silicon) that can also be an expensive mistake.
That said: 1) I deal with CPU bugs pretty regularly on Chrome. Some old CPUs behave unreliably with certain sequences of instructions and we get bursts of crashes on these CPUs with some Chrome versions. 2) Intel regularly "fixes" CPU bugs with microcode updates. 3) The Spectre family of vulnerabilities are arguably CPU bugs. 4) The Pentium fdiv bug was definitely a CPU bug.
So, CPU bugs escape to silicon all the time. Way more than I would have guessed just a few years ago. Our industry is built on a pile of wobbly sand.