It depends on how exactly you define a bug, but something like a 6502 or Z80, which has essentially all the errata well-documented since it has existed for so long, might qualify.

Z80 implementations for one had a whole slew of undocumented instructions, allegedly because they were buggy in some way.

The VIPER was built to be fully proven, but there was come debate on methodology.

stop playing lawyer ball. i'm talking about the bugs that require turning off core functionality (such as hyperthreading) and/or that lead to system halts / corrupted data.

yes it happens, but software bugs happen every day where as if your system blue screened every day you know dang well you'd be on the phone with the hardware vendor for a refund / new system.

>yes it happens, but software bugs happen every day where as if your system blue screened every day you know dang well you'd be on the phone with the hardware vendor for a refund / new system.

Well, since hundreds of millions of people use Skylake/Kaby Lake CPUs for 2 years now, and only now we learn about this, obviously this is not of the "system blue screens every day" variety but a very rare bug.

> obviously this is not of the "system blue screens every day" variety but a very rare bug

Not to be anal but we can't know this.