Amiga, Atari ST or Sharp X68000. This means even a 68060-upgraded Atari ST clone or Amiga, which avoid CPU emulation, were always slower, on top of causing some programs not to work thanks to imperfect virtualization of the Mac system and remaining machine components. Connectix also released another 68k emulator for Macs, replacing the original, called Speed Doubler, supposedly reported to be even faster than Apple's. As the years went by, the emulator wasn't updated to work with later versions of the original Mac OS, however, supposedly because Apple's own 68k emulator eventually surpassed it in performance, and the OS itself relied further on native PowerPC code with each new Mac OS update. There was also a software emulator for x86 platforms running DOS/Windows and Linux called Executor, from ARDI. ARDI reverse-engineered the Mac ROM and built a 68000 CPU emulator, enabling Executor to run most (but not all) Macintosh software, from System 5 to System 7, with good speed. The migration from 68000 to PowerPC, and the added difficulties of emulating a PowerPC on x86 platforms, made targeting the later Mac OS versions impractical. Unlicensed clones Wary of repeating history and wanting to retain tight control of its product, Apple's Macintosh strategy included technical and legal measures that rendered production of Mac clones problematic. The original Macintosh system software contained a very large amount of complex code, which embodied the Mac's entire set of APIs, including the use of the GUI and file system. Through the 1980s and into the 1990s, much of the system software was included in the Macintosh's physical ROM chips. Therefore, any competitor attempting to create a Macintosh clone without infringing copyright would have to reverse-engineer the ROMs, which would have been an enormous and costly process without certainty of success. Only one company, Nutek, managed to produce "semi-Mac-compatible" computers in the early 1990s by partially re-implementing System 7 ROMs. This strategy, making the development of competitive Mac clones prohibitively expensive, successfully shut out manufacturers looking to create computers that would directly compete with Apple's product lines. However, companies like Outbound Systems, Dynamac and Colby Systems, were able to sidestep the Mac cloning process by targeting high-end, high-profit market segments without suitable product offerings from Apple and offering Mac conversions instead. In the early 1980s, Brazil's military dictatorship instituted trade restrictions that prohibited the importation of computers from overseas manufacturers, and these restrictions were not