Specifications
The P-II could have two Channel Processors, or Chaps. Each Chap is a 4-way parallel (RGBA) image computer. The chassis could hold 4 cards. Another model, the PII-9, could hold 9 cards (4 Chaps, 2 video processors, 2 Off Screen Memory (OSM) cards, and an Overlay Board for NeWS, the PostScript-based windowing system. The extensions added were to control the image pipeline for roaming, image comparison, and stereo image viewing. The PII-9 was the imaging engine for a UNIX host. This was a SIMD architecture, which was good for imagery and video applications. It processed four image channels in parallel, one for red, one for green, one for blue, and one for the alpha channel (whose inventors have connections to Pixar).
It processed imagery in 12 bits per color channel (or 48 bits per pixel). The 12-bit data represented an unusual (for today) fixed-point format that ranged from -1.5 to 2.5 using 2 bits for the integer portion, the range from 0 to 1 had 10 bit accuracy.
The system could communicate image data externally over an 80M per second "Yapbus" or a 2M per second multibus to other hosts, data sources or disks and had a performance measured equivalent to 200 VUPS, or 200 times the speed of a VAX 11/780.
Read more about this topic: Pixar Image Computer