Some of those restrictions may include preventing some interrupts from triggering, prohibition of execution of a class of "privileged" instructions.
Additional status flags may bypass memory mapping and define what action the CPU should take on arithmetic overflow.
This can be achieved with the following assembly code: By manipulating the FLAGS register, a program can determine the model of the installed processor.
If the program tries to modify this flag and senses that the modification did not persist, the processor is earlier than the 486.
Starting with the Intel Pentium, the CPUID instruction reports the processor model.