1. IndigoTM Family Overview

As members of the IRIS 4DTM family of graphics workstations, lndigoTM systems offer the powerful, interactive 3D graphics that have made Silicon Graphics the industry leader in technical, scientific, and creative computing. As full-featured UNIXTM workstations, Indigos offer network file access, virtual memory, multitasking, and all the UNIX standards that technical users demand. As next-generation workstations, Indigo systems add new features such as DAT-quality audio processing, interchangeable CPU and graphics boards to take advantage of the most powerful technology available, and an option for live video 1/0 that make it ideal for professional multimedia authoring.

The Indigo family of workstations begins with two distinct models: the IRIS Indigo workstation and the new Indigo2TM workstation. The two models then offer a wide variety of system configurations, allowing you to buy as much workstation as you need without exceeding your budget. Both Indigo2 and IRIS Indigo have a modular design, allowing an easy upgrade of CPU board, graphics board, or memory configuration.

1.1 IRIS Indigo

Figure 1 illustrates the IRIS Indigo central unit with an attached monitor, keyboard, three button mouse and microphone. The central unit measures 15 inches high by 9.5 inches wide by 10.9 inches deep, a small box that fits easily on a bookshelf or the floor.

Figure 1 IRIS Indigo with accompanying keyboard, monitor, mouse, and microphone

The IRIS Indigo central unit houses a power supply, a speaker, a hard disk drive, and slots for additional data storage devices such as DAT and floppy disk drives. A door on the front of the unit provides easy access to removable media.

The IRIS Indigo contains two standard boards:

The front of the central unit is easy to remove for quick access to the CPU board and the graphics board. Users can easily add memory modules to the CPU board and a video option board to the graphics board. They can also add and remove internal SCSI devices - hard disk, DAT, and floppy disk drives by simply snapping them into place and closing the front panel. All front-loading drives are self-configuring, and can be effortlessly removed and re-installed at sites that require security or transportability.

1.1.1 IRIS Indigo CPUs

IRIS Indigo offers three upgradable CPU boards:

The IRIS Indigo Entry system was the first Silicon Graphics workstation designed to use the general-purpose processing power of these three CPUs to accomplish tasks that previously required more costly dedicated graphics co-processors. IRIS Indigo's state-of-the-art hardware architecture allows it to perform graphics computations at a speed that equals many machines with special-purpose graphics processors.

1.1.2 IRIS Indigo Graphics

IRIS Indigo offers several optional graphic configurations:


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1.2.1 Indigo2 CPUs

The new Indigo2 workstation comes in two, easy-to-upgrade CPU module configurations:

Indigo2 offers a new generation of system architecture designed to take full advantage of the these CPUs. The Indigo2 system buses and main memory buses have been increased to 64 bits to take advantage of the 64-bit wide processor bus of the R4000SC and R4400SC CPUS. The 64-bit wide system bus in Indigo2 runs at 400 MB per second and can transfer data at 266 MB per second. Primary data and instruction caches of 8 KB each (16 KB each in the R4400SC version) combined with I MB of secondary cache and two Fast SCSI-2 channels add to the astonishing performance of the newest member of the indigo family.

1.2.2 Indigo2 Graphics

Indigo2 comes standard with Extreme Graphics. the most powerful graphics hardware currently offered by Silicon Graphics for a desktop workstation. Extreme Graphics provides two raster engines, eight Geometry Engines, high resolution 24-bit color, and a 24-bit Z-buffer.

1.3 Indigo Technology

To accelerate data transfer between the CPU and the graphics and I/0 subsystems, all ndigo workstations use custom ASICs (Application-Specific Integrated Circuits) designed by Silicon Graphics. These chips manage memory and processor interrupts, handle I/0, control the bus, fill pixels and draw lines, control graphics output, and access color tables, often without CPU intervention. The result is a sustained data-transfer rate of up to 133 MB/second for the R3000A version and up to 266 MB/second for the R4000SC and R4400SC version's direct CPU-to-RAM transfers.

To take advantage of improving technology, IRIS Indigo clocks the CPU and system buses independently. This not only allows both the system bus and the CPU to run at maximum performance, but also allows upgrades to the CPU and graphics to occur independently.

To help speed the transfer of large blocks of data such as frames of bitmapped images used in animation, the R4000SC and R4400SC IRIS Indigo and Indigo2 workstations include a custom chip that supports Virtual DMA (Direct Memory Access). The chip knows the exact physical memory address of each page of virtual memory. A user can request DMA access to a data block using virtual memory addresses; the DMA engine provides direct access to the physical memory where the data is stored, even if the block is stored in discontinuous memory. Virtual DMA reduces interrupts and CPU overhead, and runs at maximum speed no matter how busy the operating system is.

All configurations of IRIS Indigo and Indigo2 support Fast SCSI-2 for maximum data transfer speed to SCSI devices via a SCSI-2 bus. In the Indigo2, the SCSI-2 bus operates at up to 10 MB per second on both SCSI-2 channels simultaneously. This bus can support internal hard drives of over one gigabyte of formatted capacity.

1.4 Audio and Video

All Indigo workstations offer sound accompaniment to their graphic images with an audio system that supports 24-bit digital stereo and 16-bit analog stereo sound. It includes line-level and mic- level analog inputs, line-level analog outputs and, for working directly with digital audio, a stereo serw dWW input/output jack.

Because many users want to mix incoming video with graphics and to record their work on videotape, all IRIS Indigo graphics boards include a bus to accept an add-on Silicon Graphics video board that handles composite or SVideo signals in NTSC or PAL formats.