SGI Visual Workstation is a series of workstation computers that are designed and manufactured by SGI. Unlike its other product lines, which used the 64-bit MIPS RISC architecture, the line used Intel Pentium II and III processors and shipped with Windows NT 4.0 or Windows 2000 as its operating system in lieu of IRIX. However, the Visual Workstation 320 and 540 models deviated from the architecture of IBM-compatible PCs by using SGI's ARCS firmware instead of a traditional BIOS, internal components adapted from its MIPS-based products, and other proprietary components that made them incompatible with internal hardware designed for standard PCs and hence unable to run other versions of Microsoft Windows, especially Windows 9x. By contrast, the remaining models in the line are standard PCs, using VIA Technologies chipsets, Nvidia video cards, and standard components. Computer architecture There are two series of the Visual Workstations. All are based on Intel processors; the first series (320 and 540) used SGI's ARCloader PROM and Cobalt video chipset, the remainder are essentially standard PC's. The 320 and 540 use a Unified Memory Architecture (UMA) memory system. This shares the video and system memory and runs them at the same speed, and allows for up to 80 percent of the system ram to be applied to video memory. The allocation is static, however, and is adjusted via a profile. The 320 and 540 also use the onboard Cobalt video adapter, which is SGI's proprietary graphics chipset. The firmware used in these systems is a PROM that enables booting into a graphical subsystem before the OS was loaded. In this regard they resemble the Irix/MIPS line of SGI computers such as the SGI O2. The 320 and 540 also stand out for having FireWire (IEEE 1394) ports, onboard composite/S-video capture, and USB keyboards and mice. They differ from each other in that the 320 is dual Pentium II/III-capable with 1GB maximum system RAM, while the 540 is quad Pentium III Xeon-capable with 2GB maximum system RAM. Both computers use a proprietary DIMM module that is essentially the same as ECC SDRAM PC-100, but in a package one-half normal size. The maximum memory per module is 96MB, and the SGI 320 has twelve memory slots. The FireWire ports that are built into the 320 never functioned. SGI distributed Orange Micro FireWire cards about a year after production commenced, in lieu of fixing the FireWire ports. Both