SGI Octane - Graphics Subsystem

Graphics Subsystem

Graphics on the Octane are provided by a series of cards: SI, SI+T, SSI, MXI. These are updated XIO versions of Solid Impact (SI), High Impact (SI+T) and Maximum Impact (MXI) from the SGI Indigo2 that were internally designated by SGI as 'MARDIGRAS'. The boards were accelerated and reengineered with faster geometry engine and texture modules to create their new versions: SE, SE+T, SSE, MXE. The SI/SE provides 13.5MB of framebuffer memory while the SSE and MXE have a 27MB framebuffer. The '+T' indicates an additional high speed Rambus RDRAM-based texture board which gives 4MB of texture memory, which is practically indispensable, though quite expensive and fragile. The SI/SE+T has one texture board while the MXI/MXE has 2 texture boards, however, the 2 boards in the MXI/MXE do not double the available texture memory to the system. It just doubles the texture performance.

Later Octanes and Octane2's support the SGI VPro graphics board series, designated 'ODYSSEY'. The first VPro series cards were the V6 and V8. The main differentiator being that the V6 has 32MB of RAM (unlike the MARDIGRAS option, framebuffer memory and texture memory come from the same pool) and V8 having 128MB. Later, the V10 (32MB) and V12 (128MB) were introduced. The main difference with the new VPro V10/V12 series is that they had double the geometry performance of the older V6/V8. V6 and V10 can have up to 8MB RAM allocated to textures (2X more than the textured-enabled MARDIGRAS options), while V8 and V12 can have up to 108MB RAM used for textures.

The VPro graphics subsystem consists of an SGI proprietary chip set and associated software. The chip set consists of the buzz ASIC, pixel blaster and jammer (PB&J) ASIC, and associated SDRAM.

The buzz ASIC is a single-chip graphics pipeline. It operates at 251 MHz and contains on-chip SRAM. The buzz ASIC has three interfaces:

• Host (16-bit, 400-MHz peer-to-peer XIO link)
• SDRAM (The SDRAM is 32 MB (V6 or V10) or 128 MB (V8 or V12); the memory bus operates at half the speed of the buzz ASIC.)
• PB&J ASIC

As with the MARDIGRAS boards, all VPro boards support the OpenGL (MARDIGRAS is OpenGL 1.1 + SGI Extensions, while VPro upgraded support to OpenGL 1.2) and OpenGL ARB imaging extensions, allowing for hardware acceleration of numerous imaging operations at real-time rates.