IRIS Crimson

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The IRIS Crimson is an older SGI system released in the early 1990s. It was the first workstation released with a 64-bit processor.

Crimson was a member of Silicon Graphics's IRIS 4D series of deskside systems; it was also known as the 4D/510 workstation. It was similar to other SGI IRIS 4D deskside workstations, and could utilise a wide range of graphics options (up to Reality Engine). It was also available as a file server with no graphics. This machine was made famous with its brief cameo in the movie Jurassic Park where the granddaughter of Hammond, Lex, was using the machine to navigate the filesystem in 3D on IRIX 4.0 using the IRIX application FSN in order to restore power to the compound.


An SGI Crimson, complete with Monitor, Keyboard, Mouse and Optional potted plant.
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  • One superpipelined MIPS 100 MHz R4000 or 150 MHz R4400 processor;
  • Choice of seven high performance 3D graphics subsystems deliver performance and features to match any application;
  • Up to 256 MB memory and internal disk capacity up to 7.2 GB, expandable to greater than 72 GB using additional enclosures.
  • High performance I/O subsystem includes four VME expansion slots, Ethernet and two SCSI channels with disk striping support.
  • Seven graphics configuration:
  • S, no display, only server
  • Entry with LG1/2 board and VME adaptator, the same board as the Indigo
  • Express, ELAN board and vme adaptator, same board as the indigo
  • Clover2,GTX and GTX(B) boardset
  • Powervision, VGX and VGXT boardset
  • Venice, Reality Engine boardset


The memory modules are the same as the MC2 memory board, but unlike other Iris4D series machines the MC2 is not reconised by the system.

The minimal configuration consists of two cards: IP 17 and IO3B.

While the MIPS R4000 is a 64-bit processor, the Crimson is only capable of running it in 32-bit mode.

The IRIS Crimson will run up to IRIX 6.2, but there are bugs in the fx.IP17 in the IRIX 6.2 release. In order to prepare a drive you will either need an earlier version of fx, or run fx on another system to partition the drive.

- IP17

This card supports a 100MHz R4000 or 150MHz R4400 CPU with 1MB L2 memory cache and the memory sub-system.

The bus frequency is half of the core speed, 50MHz or 75MHz.

The differences between the two versions are the prom revision and some different logic on the board. An upgrade is possible by swapping the CPU and crystal to obtain a 120MHz one.

The Crimson does not support any MC2, the main memory is locked at 256MB.

The Crimson supports only one IP17 board.

- IO3b

It's the Input Outut board and support:

  • two SCSI channels driven with Western Digital 33C93, one for internal and one for external devices
  • two Centronics connectors on the chassis
  • 4 serial ports
  • 1 parallel port
  • AUI 10Mb ethernet port
  • 3 Powered Peripheral Ports (8 Pin DIN)

VGX(T) configuration, AKA POWERVISION

The VGX(T) Graphics PIPE is the first to support hardware texture mapping.

The VGX was released in the end of 1989, and was followed by the GVXT (T seems to mean Turbo, because of the fill rate enhancement)

The VGX(T) was designed to support IrisGL, it was a really powerful gfx pipe before the introduction of the Reality Engine, but it has a poor texture memory size of 256KB. Also, because of its architecture, it is slow on certain OpenGL operations.

The pipe is composed of the following cards.

  • GM3 and GM3b, the pipe headquarter, driven by a 16MHz Motorola 68020, a surge of the old 68k workstation.

the GM3 and GM3b have a DB9 serial port, you can plug a serial terminal to access internal monitoring

Its job is to dispatch the data and GL instructions to the GE and RM.

  • GE6 is the Geometry Engine Board, it contains 8 Texas Instruments DSPs, each rated for 32Mflops. The documentation describes 4 GE chips, in fact 4 are used for the T&L and the remaining 4 are used for other geometric operations.

  • RM2 and RM3, these cards have the same function; the RM2 is used on the VGX and the RM3 is used on the VGXT.

The Raster Manager's job is to do representation of the 3D data in 2D, it contains the framebuffer, texture and Zbuffer memory.

20 IMP3 (image processor chip) for VGX and IMP5 for VGXT do the rasterisation and it work with tiles for each IMP.

The differences between VGX and VGXT are included in the RM board:

  • RM3 do higher texel fill rate, 50Mpixel/s vs 17Mpixel/s
  • RM3 do per pixel fog and haze computations, RM2 don't
  • RM3 do per pixel perspective correction for textures, RM2 don't
  • RM3 do better Tram usage and can span memory boundaries, RM2 don't

VGX and VGXT support 1 or 2 Raster Manager boards (RM2 and RM3), providing twice the pixel performance.

  • DG1 do the digital to analog conversion to drive the display, it contains the RAMDAC

  • DG/VX1 permit to use two GVX(T) pipes in one rack, and to drive one or two displays. This is a part of a rack system configuration named SKYWRITER.

Some GM3 can work with the VGXT boardset, but RM2 cannot be mixed with RM3 boards.


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