It is doubtful they cared one bit. The 186 was really targeted at the embedded market (which is why it integrated so much of the usual support chips roles onbo

It is doubtful they cared one bit. The 186 was really targeted at the embedded market (which is why it integrated so much of the usual support chips roles onboard the CPU). So it did not likely figure much here. For the 286, do keep in mind that prior to IBM releasing the PC-AT, no one at Intel likely considered that anyone would want to use their newfangled 286 as nothing more than a "fast 8086". It appears that Intel's plan for the 286 was that everyone would also have a 286 protected mode OS to run upon it, and 8086 real mode was included only for the purposes of setting up the minimum necessary protected mode data tables to enable a switch into protected mode. This is one of the reasons why the 286 provided no documented way to leave protected mode once the OS flipped the PE bit in CR0 to 1. And, in 'protected mode' one has to provide protection against executing invalid opcodes for it to be properly a 'protected mode'. The fact that most 286 system purchasers were running their shiny new 286 as nothing more than a fast 8086 for many years probably caused much more consternation at Intel than the fact that the [12]86's generated exceptions for undocumented 8086 opcodes.