NeXTSTEP '486 will not work with the graphics accelerators now popular in the PC marketplace but will instead require a new generation of PC display adapters that give the '486 CPU direct access to screen memory Ð essentially using the '486 itself as the accelerator. "We build a window server that is highly tuned for a linear frame buffer," said Bob Lawton, program manager for NeXTSTEP '486. The speedy Display Post-Script performance on NeXT hardware will port directly to NeXTSTEP '486 if the PC also has a linear frame buffer that allows the '486 CPU to directly access all screen memory.
But, Lawton explained, most current PC video adapters do not give the CPU direct access.
When NeXT first demonstrated NeXTSTEP '486 in January 1992, it was on a Dell '486 equipped with a special JAWS screen adapter. Dell's JAWS implementation uses an Intel specification to build two complete video subsystems Ð memory-mapped video and VGA Ð and combine the separate outputs with a video mixer.
Although NeXTSTEP '486 does not use VGA, Dell includes it for DOS and Windows users.
Now two companies Ð Chips and Technologies, and ATI Technologies Ð have developed single-chip video-display controllers that provide NeXTSTEP with a linear frame buffer that also implements a complete VGA. Both chips have a maximum screen resolution of 1280 by 1024 pixels with 16 bits per pixel Ð perfect for supporting color Display PostScript.
With Chips and Technologies' Wingine chip, a PC maker places the video memory directly on the CPU's memory bus. The Wingine reads from video memory and sends the data to a high-speed video D/A (digital-to-analog) con- verter. "Wingine is a bottleneck reducer," said Dr. Scott Cutler, vice-president of software for Chips and Technologies. "We put the video memory on the memory controller. Logically it appears as another bank of SIMMs."
Systems must be specially redesigned to use the $15 chip; two system makers who have already done so are Epson and Lucky Goldstar.
ATI's chip, the mach32, is optimized for Intel's new PCI (Peripheral Component Interconnect) bus and should sport similar performance. The $75 chip also provides many graphics-acceleration features that, while unused by NeXTSTEP, may make the chip popular with DOS and Windows users.
On video adapters that do not support any linear-frame-buffer mode Ð including most existing VGA and SVGA systems Ð NeXT- STEP '486 will be only run in grayscale mode.