The cost would not have been very big. The 8086 had microcode, and there were the very similar LDS and LES instructions. There were plenty of unused slots in

The cost would not have been very big. The 8086 had microcode, and there were the very similar LDS and LES instructions. There were plenty of unused slots in the opcode table so that wasnt it the reason either. There are weird instructions aplenty like XLAT or AAA/AAS/AAD/AAM, so it wasnt as if they had a pressing silicon shortage. Maybe they dindt think about it, and fixed it with a quick hack once they got aware of the problem? The whole segment register story was very hacky from the start. Intel might have dumped the segment registers in i386 32 bit protected mode, as they cleaned up a lot of other troublesome corners around that time. But, well, they didn't, so we have to deal with it today.