alt Hacker NewsNo discussion of these instructions on the 386 would be complete without mentioning that early revisions had a bug in the 32-bit multiply: https://retrocomputing.stackexchange.com/questions/17803/int...
I wonder if anyone outside of Intel has discovered the actual bug in the circuitry yet.
Yes, one can only hope Ken Shirriff eventually happens to come across one of those models, but I guess they are probably very rare these days.
Besides the multiplication, the 386 had quite a number of teething problems[1], including occasionally broken addressing modes, unrecoverable exceptions, virtual address resolution bugs around the 2G mark, etc...
A while ago, there was also an article posted here that analyzed the inner workings of the Windows/386 loader[2]. Interestingly, Windows simply checks a pair of instruction (XBTS/IBTS) that early 386 steppings had, but was later removed, raising an invalid opcode exception instead.
Raymond Chen also wrote a blog post describing a few workarounds that Windows 95 had implemented[3].
[1] https://www.pcjs.org/documents/manuals/intel/80386/
[2] https://virtuallyfun.com/2025/09/06/unauthorized-windows-386...
[3] https://devblogs.microsoft.com/oldnewthing/20110112-00/?p=11...