Not directly related to the 8086 per se, but should you ever have a look at the (80)386, a question that I always had was whether the perpetually reserved contr

Not directly related to the 8086 per se, but should you ever have a look at the (80)386, a question that I always had was whether the perpetually reserved control register CR1 (CR2 and CR3 already appeared in the 386 as well, and later generations added CR4, but CR1 remained reserved) ever had any meaning that could actually be found in hardware. I went so far as asking the chief engineer of the 386, but only got a short answer back confirming that it is “reserved”. The closest I got to a promising answer was when talking with the maintainer of os2museum.com, who, based on pre-release data sheets of the 386, speculated that it may have been a control register for the removed on-chip cache. But I’m still wondering if accesses to CR1 are just hardcoded to be undefined instructions, or if there is something somewhere.