Anyone know what in particular the 486SX had that the 386 didn’t to make keeping only the former alive practical? Unfortunately the kernel mailing list link in the zdnet article appears to be rotted away.
I believe 386 did not have certain "atomic" instructions like CMPXCHG or XADD. So in order to support 386, the kernel had to have special versions of all locking primitives just for 386.
