A Whole Lotta Buffers

While a single smart processor like the Glint 300SX can speed up 3-D rendering substantially, there's no substitute for lots of buffer space. Like other Intergraph GLZ adapters, the 24-MB GLZ2 employs a 220-bit-wide memory bus to service 92 video planes consisting of two 24-bit RGB buffers (double buffering for smooth animation) and one 24-bit Z-buffer that caches depth information. Masking, overlay, and image window-control bits account for the remaining 20 video planes.

The GLZ2 uses four custom proprietary Intergraph ASIC subsystems for 2-D and 3-D graphics acceleration. The DMA Engine is the main graphics acceleration processor; according to Intergraph, it touts 3-D speeds of up to 450,000 Gouraud-sh aded triangles per second. The PCI/DMA ASIC controls vertex data flow (the vertices of surface polygons) up to burst speeds of 4 MBps to and from the PCI bus and the GLZ2's 24 MB of VRAM to the FIFO chip subsystem. The four-ASIC Resolver subsystem controls RGBA (RGB and Alpha channel) pixel and Z-data I/O to the frame buffer. A 256-bit-wide Analog Devices ADV7160 DAC handles color conversion.

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GLZ2 Not Just Glitz

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Omnicomp's 3Demon SX48 provides substantial acceleration with OpenGL, but the TDZ-40's GLZ2 subsystem is faster still. The SX48 keeps up only in its 12-bit color mode, which isn't a fair comparison.