graphics hardware (GF2 Frame Buffer, UC4 Update Controller, DC4 Display Controller, BP3 Bitplane). Their main differences were the CPU, RAM, and Weitek Floating Point Accelerator boards, disk controllers and disk drives (both ST-506 and SMD were available). These could be upgraded, for example from a 2400 to a 2400T. The 2500 and 2500T had a larger chassis, a standard 6' 19" EIA rack with space at the bottom for two SMD disk drives weighing approximately each. The non-Turbo models used the Multibus for the CPU to communicate with the floating point accelerator, while the Turbos added a ribbon cable dedicated for this. 60 Hz monitors were used for the 2000 series. The height of the machines using Motorola CPUs was reached with the IRIS 3000 series (models 3010/3020/3030 and 3110/3115/3120/3130, the 30s both being full-size rack machines). They used the same graphics subsystem and Ethernet as the 2000s, but could also use up to 12 "geometry engines", the first widespread use of hardware graphics accelerators. The standard monitor was a 19" 60 Hz non-interlaced unit with a tilt/swivel base; 19" 30 Hz interlaced and a 15" 60 Hz non-interlaced (with tilt/swivel base) were also available. The IRIS 3130 and its smaller siblings were impressive for the time, being complete UNIX workstations. The 3130 was powerful enough to support a complete 3D animation and rendering package without mainframe support. With large capacity hard drives by standards of the day (two 300 MB drives), streaming tape and Ethernet, it could be the centerpiece of an animation operation. The line was formally discontinued in November 1989, with about 3500 systems shipped of all 2000 and 3000 models combined. RISC era With the introduction of the IRIS 4D series, SGI switched to MIPS microprocessors. These machines were more powerful and came with powerful on-board floating-point capability. As 3D graphics became more popular in television and film during this time, these systems were responsible for establishing much of SGI's reputation. SGI produced a broad range of MIPS-based workstations and servers during the 1990s, running SGI's version of UNIX System V, now called IRIX. These included the massive Onyx visualization systems, the size of refrigerators and capable of supporting up to 64 processors while managing up to three streams of high resolution, fully realized 3D graphics. In October 1991, MIPS announced the first commercially available 64-bit microprocessor, the R4000. SGI used the R4000 in its Crimson