Protection for "mask works" was introduced in the Semiconductor Chip Protection act of 1984. You'll see a circled-M on modern dies indicating this protection. (

Protection for "mask works" was introduced in the Semiconductor Chip Protection act of 1984. You'll see a circled-M on modern dies indicating this protection. (I got the mask work symbol added to Unicode recently, but font support is lacking: 🆭.) The 8086 is the only chip I've seen with a copyright specifically designating the microcode.