O2 / O2+



SGI O2 front with classic cube design.

The Silicon Graphics O2 (codename "Moosehead") may be considered a successor to the Indy line of desktop workstations. It is also placed at the lower end of the Silicon Graphics product line and like the Indy the O2 features integrated video capabilities. The O2 like the Indy was designed with a focus on video and multimedia applications.

In 2001 the Silicon Graphics O2+ extends and updates the original O2 series from 1996, but offers no change in the underlying architecture. To let SGI speak here: "This workstation is a value-rich version of the Silicon Graphics O2 visual workstation. It has all the benefits and integrated features of the O2 workstation, plus twice the system memory, and two times the system disk capacity, a new high-performance processor, and a new purple color."

Twice the system memory and disk capacity refers to the basic system configuration. So aside from being available with other CPU options the O2+ is technically an O2.

Architecture Overview

What sets the O2 aside from other systems designed by Silicon Graphics is it's Unified Memory Architecture (UMA). At the core of the system architecture is the Memory & Rendering (MRE) ASIC which includes direct paths to all subsystems of the O2 including CPU, Memory, I/O, compression, display and imaging.

Unlike other Silicon Graphics computers the O2 does not have graphics as an optional part. The O2 graphics hardware is highly integrated in to the systems core components. This makes the O2 the only Silicon Graphics system which cannot be ordered without graphics installed and also the only one where there is no choice of graphics options.


1996, October
Introduction of O2 family
1998, February
Dual display solution announced
1998, May
250 MHz R10000 processor introduced for O2 series
1998, July
225 MHz R10000 processor replaces 175/195 systems
1999, April
270 and 300 MHz R10000 processors announced. Standard system configurations enhanced.
1999, July
Availability of QED RM5200 processor running at 300 MHz announced
2000, July
New processor: 400 Mhz R12000A with 2MB secondary cache
2001, August
O2+ announced at SIGGRAPH 2001 in Los Angeles, California
2002, May
End of Production (EOP) announced for O2 and O2+
2002, September
End of Production
2007, September
End of Service


R5000 vs. R10000

O2 mainboard. RM5200 CPU board hidden under PCI riser.

Typically O2 systems are either equipped with R5000 baseed or R10000 based CPUs. The most obvious difference is that R10000 based systems lack one of the harddisk slots in the system. This is caused by a larger heatsink that is required for R10000/R12000 processors. This also results in some mechanical differences which makes upgrading between the two CPU lines complicated. Aside from the physical differences it is possible to run any O2 CPU on any O2 mainboard.

R5000 based options

CPU Board Processor Clockspeed Cache (d/i) Cache (2nd) Floating Point
IP32 R5000PC 180 MHz 32kb / 32kb 0MB onboard
IP32 R5000SC 180 MHz 32kb / 32kb 512KB onboard
IP32 R5000SC 200 MHz 32kb / 32kb 1MB onboard
IP32 RM5200SC 300 MHz 32kb / 32kb 1MB onboard
IP32 RM7000A 350 MHz 32kb / 32kb 256KB (1MB tertiary) onboard

The RM5200SC CPU is not recognized by the hinv command. It is reported as an R5000SC processor.

R10000 based options

CPU Board Processor Clockspeed Cache (d/i) Cache (2nd) Floating Point
IP32 R10000 150 MHz 32kb / 32kb 1MB onboard
IP32 R10000 175 MHz 32kb / 32kb 1MB onboard
IP32 R10000 195 MHz 32kb / 32kb 1MB onboard
IP32 R10000 225 MHz 32kb / 32kb 1MB onboard
IP32 R10000 250 MHz 32kb / 32kb 1MB onboard
IP32 R12000 270 MHz 32kb / 32kb 1MB onboard
IP32 R12000 300 MHz 32kb / 32kb 1MB onboard
IP32 R12000 400 MHz 32kb / 32kb 2MB onboard


Type:                   139pin SDRAM DIMMs (proprietary) 
Sockets:                8 (4 * 2 sockets)

Minimum configuration:  32 MB (2 * 16 MB DIMMs)
Maximum configuration:  1024 MB (8 * 128 MB DIMMs) 

To install high density (128 MB DIMMs) flash PROM revision 4.4 or higher is required (see hinv). With older PROM revisions maximum memory is 256 MB. For IRIX 6.3 there are patches to upgrade the PROM, for IRIX 6.5 these come with the operating system and overlays. Usually this means that once a recent version of IRIX has been installed the PROM has been upgraded to a newer revision.

Original SGI DIMMs are color coded. The color markings on the top side of the modules give a hint at their size. Code number one is on the top corners, code number two in the top middle. The following table explains the data for a single module (taken from manual 007-3778-002 "Silicon Graphics O2 Workstation Memory Installation Instructions"):

 Size     Code 1      Code 2      SS/DS       Type
16 MB     Purple      -           SS          A
32 MB     Yellow      -           DS          A
64 MB     Green       White       SS          B
128 MB    Silver      -           DS          A
128 MB    Silver      White       DS          B

                                  SS - single sided
                                  DS - double sided 



The O2 (O2+ as well) has no removeable graphics option. 3D calculations are done on the main CPU but there is hardware support for some advanced features (z-buffer, image mapping, ...) on the MRE. The Unified Memory Architecture allows all parts of the system access to the main memory. There is no need for additional texture or z-buffer memory.

A dual head adapter is available for the builtin graphics option.

PsiTech made a PCI board that could be used as a graphics head in a O2 system. A local copy of the data sheet can be found over here.


Drives / SCSI Devices

The O2 has onboard support for SCSI devices. It has one internal and one external Adaptec 7880 Ultra Wide SCSI controller. One of these controllers supports the internal disks (SCA) and CD-ROM while the other services the external SCSI port (wide SCSI).


Back of an O2 with AV module installed.

  • Multimedia:
    • Microphone
    • 2 Stereo Audio (Cinch)
  • Networking:
    • 10/100MBit BaseT Ethernet
  • Input/Output:
    • PS/2 port for keyboard and mouse
    • DB9 serial ports
    • IEEE-1284C parallel port
  • Graphics:
    • HD15 monitor connector (VGA compatible)


Expansion Slots

The O2 has 1 PCI64 expansion slot on a riser card. Also, there is a proprietary slot for audio/video options.

Video/Graphics Options

Side view of an O2 with AV module installed.

The Analog Video Option (AV1) and the Digital Video Option (AV2) are installed in the purpose built slot on the right of the drive bays.

Related to the graphics output are the following options:

  • Dual Head option
  • 1600SW flat panel adapter
  • Presenter flat panel adapter

PCI cards

See also the Nekochan hardware Aggregator linked below. The options include FDDI, SCSI, Firewire (IEEE 1394), Ethernet.


The O2 chassis has the following dimensions:

width:     22,86 cm / 9"
height:    30,48 cm / 12"
depth:     26,67 cm / 10.5"

weight:    9.9 kg / 22 lbs 

There are no color codes or other obvious markings for different CPU models. Old O2 models feature the classic Silicon Graphics logo with cube while newer models have the "SGI" logo. As stated in the beginning the color of the plastic skins was changed from green to purple for the O2+ models.

The O2 chassis has 2 drivesbays for SCA SCSI devices on its back in which the drives are mounted on a drivesled. One of these is not useable on R10000 based models of the O2 because the space is required to ensure proper cooling of the CPU.

Aside from the "normal" desktop workstation there is also a rackmountable version of the O2 that has slightly different dimensions:

width:     19,69 cm / 7.75"
height:    26,67 cm / 10.5"
depth:     22,86 cm / 9.0"

weight:    7,65 kg / 17 lbs


Rebadged Systems

The O2 was also sold as a relabeld system by other vendors. One of these systems that is known is the Siemens Nixdorf RW510.

Special Configurations

Silicon Graphics sold the WebFORCE O2 as an authoring and serving solution for the World Wide Web including a special software package:

  • Cosmo Create: WYSIWYG HTML page layout tool
  • Cosmo Worlds: the definitive VRML authoring system
  • Cosmo Code: visual Java development environment
  • Adobe Photoshop: image processing software
  • Adobe Illustrator: illustration software
  • Kai's Power Tools: image processing software for Photoshop
  • Digital media tools: everything you need to create rich, multimedia content
  • Netscape FastTrak server: Web server software
  • Xing Streamworks Server: low bit rate MPEG1 streaming video serving

Colorbus O2

Like the Indy the O2 was used with Cyclone RIP system which were used for Printers or Copiers. The actual RIP is on a PCI card which is added to a stock O2. The software running on these systems seems to include a customized IRIX version - especially the kernel seems to be modified as some of the systems memory isn't visible in hinv when IRIX is running (though it is there physically as well as in the PROM hinv).


Operating System

Choosing an operating system.

When the O2 was introduced the system specific IRIX 6.3 was released for the R5000 and R10000 models. The O2 is also supported by IRIX 6.5 including the final release IRIX 6.5.30.

Regardless of the system configuration it is always recommended to use IRIX 6.5.30.


Precautions to take when doing maintenance on an O2.

On many modern systems (including) the octane the power switch on the front is what is sometimes called a soft power switch as it doesn't fully disconnect the computer from the electric circuit. It is highly recommended (as is for almost all other systems) to power down the system *and* to unplug the powercord before doing maintenance on the hardware. The only exception are when the manuals explicitly tell you to do otherwise (on RAID systems that might be the case).

On the O2 this is of special importance as there have been several reports of systems that have been damaged while removing the system module while the power cord was still plugged in. Doing so is a real bad idea so double check that the system is disconnected from the power source before opening it.

If you read this too late, you might be in for some serious trouble. Check for discussions in comp.sys.sgi.hardware or try explaining your problem in the nekochan forum.

Removing the Skins

How to open the O2 to replace the CD-ROM drive.

To get a chance to replace a broken CD-ROM drive on an SGI O2 one must first carefully strip the upper part of of the O2 of it's skins. On first glance there is no obvious way so here is a short description of the procedure.

Manually eject the CD-ROM tray and remove the front bezel by pushing it up while holding the tray steady.

Carefully remove the PSU cover, there is an obvious latch to do so.

Remove black top cover: Look underneath the hood on the backside. There is a black latch that must be pressed in the direction of the chassis to release the top cover. It comes off easily.

Unlock the two screws to release the green skins from the metal chassis and remove the plastics.

Remove the two screws that hold the drive cage.
Disconnect and unscrew the drive.

That's it: Replace and reassemble. Do not forget to choose a proper SCSI ID for the CD-ROM drive before putting the covers back on.

CD-ROM Failure

What to do when the drive tray is stuck / won't work.

The CD-ROM drive used in O2 systems is a drive made by Toshiba. A common point of failure for these devices is a gear in the mechanism that opens/closes a tray. If the gear is pushed from the motor shaft it has to be installed on the CD-ROM door will refuse to open or will not close.

To fix the problem the O2 has to be disassembled so far that the CD-ROM drive can be removed. The top cover of the CD-ROM drive also has to be removed and the small -usually white- gear has to be placed back on the empty motor shaft.



SGI O2 front with classic cube design.

Side view of an O2 with AV module installed.

Back of an O2 with AV module installed.

O2 mainboard. RM5200 CPU board hidden under PCI riser.

O2 AV module

Harddisk mounted in O2 bracket.