Wikipedia
NeXTdimension (ND) was an accelerated 32-bit color board manufactured and sold by NeXT from 1990 that gave the NeXTcube color capabilities with PostScript planned. The NeXTBus, a NuBus like implementation card was a full size card for the NeXTcube, filling one of four slots, another one being filled with the main board itself. The NeXTdimension featured S-Video input and output, RGB output, an Intel i860 64-bit RISC processor at 33 MHz for Postscript acceleration, 8-32MB RAM main memory and 4MB VRAM for a resolution of 1120*832 at 24-bit color plus 8-bit alpha channel. An onboard C-Cube CL550 chip for MJPEG video compression was announced, but never shipped. A handful of engineering prototypes for the MJPEG daughterboard exist, but none actually function.
A stripped down Mach kernel was used as the operating system for the card. Due to the supporting processor, 32-bit color on the NeXTdimension was faster than 2-bit grayscale Display PostScript on the NeXTcube. Display Postscript never actually ran on the board so the Intel i860 never did much more than move blocks of color data around. The Motorola 68040 did the crunching and the board, while fast for its time, never lived up to the hype. Since the main board always included the grayscale video logic, adding a NeXTdimension allowed the simultaneous use of two monitors. List price for a NeXTdimension sold as an add-on to the NeXTcube was $US 3,995.