Internally the G400 is a 256-bit processor, using what Matrox calls a "DualBus" architecture. This is an evolution of G200's "DualBus", which had been 128-bit. A Matrox "DualBus" chip consists of twin unidirectional buses internally, each moving data into or out of the chip. This increases the efficiency and bandwidth of data flow within the chip to each of its functional units. G400's 3D engine consists of 2 parallel pixel pipelines with 1 texture unit each, providing single-pass dual-texturing capability. The Millennium G400 MAX is capable of 333 megapixels per second fillrate at its 166 MHz core clock speed. It is purely a Direct3D 6.0 accelerator and, as such, lacks support for the later hardware transform and lighting acceleration of Direct3D 7.0 cards.