In designing a x86 compatible chip, compatibility in the instruction level must be validated at first. It is impossible in quantity to make test vectors which covers every combiation of instructions, so we use a programs running in PC to test the instruction model. This paper describes the design of a IBM PC/AT environment model without great loss of emulation speed. Add to that, it shows the consideration for pre-silicon validation of x86 MPU in programer's view point and the debugging facility. Most of DOS programs, including EMM386 and MS-Windows, run on this PC environment model with CPU behavioral-description model.
