A workstation is a special computer designed for technical or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems. The term workstation has also been used loosely to refer to everything from a mainframe computer terminal to a PC connected to a network, but the most common form refers to the group of hardware offered by several current and defunct companies such as Sun Microsystems, Silicon Graphics, Apollo Computer, DEC, HP and IBM which opened the door for the 3D graphics animation revolution of the late 1990s. Workstations offered higher performance than mainstream personal computers, especially with respect to CPU and graphics, memory capacity, and multitasking capability. Workstations were optimized for the visualization and manipulation of different types of complex data such as 3D mechanical design, engineering simulation (e.g. computational fluid dynamics), animation and rendering of images, and mathematical plots. Typically, the form factor is that of a desktop computer, consist of a high resolution display, a keyboard and a mouse at a minimum, but also offer multiple displays, graphics tablets, 3D mice (devices for manipulating 3D objects and navigating scenes), etc. Workstations were the first segment of the computer market to present advanced accessories and collaboration tools. The increasing capabilities of mainstream PCs in the late 1990s have blurred the lines somewhat with technical/scientific workstations. The workstation market previously employed proprietary hardware which made them distinct from PCs; for instance IBM used RISC-based CPUs for its workstations and Intel x86 CPUs for its business/consumer PCs during the 1990s and 2000s. However by the late 2000s this difference disappeared, as workstations now use highly commoditized hardware dominated by large PC vendors, such as Dell and HP & Fujitsu, selling Microsoft Windows or GNU/Linux systems running on x86-64 architecture such as Intel Xeon or AMD Opteron CPUs.