If you write an MVC statement with an equated value as the

sending operand, then the assembler will try to resolve that

operand value as a base and displacement, it will not

necessarily throw an error at assembly, but the results at

execution will be unpredictable and may well give rise to a

protection exception.

The point of the MVI statement is that the single byte

sending operand value is assembled as part of the

instruction itself and does not have to be 'fetched' at

execution time, therefore if you are only moving a single

byte of fixed value, then an MVI will be marginally more

efficient than an MVC