As the core advocates later left the company, the MIPS-based line of computers was shut down in favor of the Alpha-based computers, a DEC invented and owned architecture, descended from the Prism development work. The first generation of commercially marketed DEC Alpha systems, the DEC 3000 AXP series, were similar in some respects to contemporaneous MIPS-based DECstations, which were sold alongside the Alpha systems as the DECstation line was gradually phased out. Both used the TURBOchannel expansion bus for video and network cards, as well as being sold with the same TURBOchannel option modules, mice, monitors, and keyboards. Later DECstations planned to be based on the ECL-based R6000 were canceled on 14 August 1990 after Bipolar Integrated Technology failed to deliver sufficient volumes of the microprocessor, which was difficult to fabricate. Yields of the R6000 were further reduced as DEC required the little-endian mode used from the beginning to continue to be available. The MIPS-based DECstations were used as the first target system and development platform for the Mach microkernel, as well as early development of the Windows NT operating system. Shortly prior to the release of the DEC Alpha systems, a port of OSF/1 to the DECstation was completed, but it was not commercially released. More recently, various free operating systems such as NetBSD and Linux/MIPS have been ported to the MIPS-based DECstations, extending their useful life by providing a modern operating system. The GXemul project emulates several of these DECstation models. The original MIPS-based DECstation 3100 was followed by a cost reduced 2100. The DECstation 3100 was claimed to be the world's fastest UNIX workstation at the time. When it was introduced it was about three times as fast as the VAXstation 3100 which was introduced at about the same time. Server configurations of DECstation models, distributed without a framebuffer or a graphics accelerator, both Turbochannel and Q-bus based, were called "DECsystem" but should not be confused with some PDP-10 machines of the same name. Early models of the DECstation were heavily integrated systems with little expansion capability and do not even possess expansion buses. The DECstation 5000 systems, introduced later, improved on the lack of expansion capabilities by providing the TURBOchannel Interconnect. The DECstation 5000 systems are also ARC (Advanced RISC Computing) compatible. The last DECstation models focused on increased component integration by using more custom ASICs to reduce the number of discrete components.