The SGI Visual Workstations (models 320 and 540) are based around the Cobalt, Lithium, and Arsenic ASICs. The Cobalt ASIC is the main system ASIC which interfaces the 1-4 IA32 cpus, the memory system, and the I/O system in the Lithium ASIC. The Cobalt ASIC also contains the 3D gfx rendering engine which renders to main system memory -- part of which is used as the frame buffer which is DMA'ed to a video connector using the Arsenic ASIC. A PIIX4 chip and NS87307 are used to provide legacy device support (IDE, serial, floppy, and parallel). The Visual Workstation chipset largely conforms to the PC architecture with some notable exceptions such as interrupt handling.