It can be considered a fourth mode of instruction sequencing after ordinary sequential execution, branching, and interrupting.
[13] Fewer 1970s designs include execute instructions: the Nuclear Data 812 minicomputer (1971) (XCT),[14] the HP 3000 (1972) (XEQ),[15] and the Texas Instruments TI-990 (1975)[16] and its microprocessor version, the TMS9900 (1976) (X).
However, some architectures implement variants of the execute instruction which inhibit branches.
[10] Some architectures support an execute instruction which operates in a different protection and address relocation mode.
[22] Similarly, the KL10 variant of the PDP-10 supports the privileged instruction PXCT 'previous context XCT'.