Michael G. Lavelle

FBRAM: a new form of memory optimized for 3D graphics

FBRAM, a new form of dynamic random access memory that greatly accelerates the rendering of Z-buffered primitives, is presented. Two key concepts make this acceleration possible. The first is to convert the read-modify-write Z-buffer compare and RGB&agr; blend into a single write only operation. The second is to support two levels of rectangularly shaped pixel caches internal to the memory chip. The result is a 10 megabit part that, for 3D graphics, performs read-modify-write cycles ten times faster than conventional 60 ns VRAMs. A four-way interleaved 100MHz FBRAM frame buffer can Z-buffer up to 400 million pixels per second. Working FBRAM prototypes have been fabricated.