When IBM announced the IBM PC in 1981, other companies such as Compaq decided to offer clones of the PC as a legal reimplementation from the PC's documentation or reverse engineering. Because most of the components, except the PC's BIOS, were publicly available, all Compaq had to do was reverse-engineer the BIOS. The result was a machine with similar performance and lower price than the machines cloned. The use of the term "PC clone" to describe IBM PC compatible computers fell out of use in the 1990s; the class of machines it now describes are simply called PCs, but the early use of the term "clone" usually implied a higher level of compatibility with the original IBM PC than "PC-Compatible", with (often Taiwanese) clones of the original circuit (and possibly ROMs) the most compatible (in terms of software they would run and hardware tests they would pass), while "legitimate" new designs such as the Sanyo MBC-550 and Data General One, while not infringing on copyrights and adding innovations, tended to fail some compatibility tests strongly dependent upon detailed hardware compatibility (such as ability to run Microsoft Flight Simulator, or any software that bypassed the standard software interrupts and directly accessed hardware at the expected pre-defined locations, or—in the case of the MBC-550 for example—wrote diskettes which could not be directly interchanged with standard IBM PCs).