The O2 is an entry-level Unix workstation introduced in 1996 by Silicon Graphics (SGI) to replace their earlier Indy series. Like the Indy, the O2 used a single MIPS-based CPU and was intended to be used mainly for multimedia. Its larger counterpart was the SGI Octane. The O2 was SGI's last attempt at a low end workstation.
Originally known as the "Moosehead" project, the O2 architecture
features a proprietary high-bandwidth Unified Memory Architecture
(UMA) that connects the various system components. A PCI
bus is bridged onto the UMA with one slot available. It has a designer case and an internal modular construction. It has space for two SCSI drives mounted on special sleds (1 in the later R10000/R12000 models due to heat constraints) and an optional video capture / sound cassette mounted on the far left side. Further information on the design and construction of the O2 can be found in the SGI
service manuals. Detailed breakdown pictures and a IRIX hinv dump can be found here
The O2 comes in two distinct CPU flavours; the low-end MIPS 180-350 MHz R5000/RM7000 based units and the higher-end 150-400 MHz R10000/R12000 based units. The 200 MHz R5000 CPUs with 1 MB L2-cache are generally noticeably faster than the 180 MHz R5000s with only 512 KB cache. There is a hobbyist project
that has successfully retrofitted a 600 MHz RM7xxx MIPS processor into the O2.
There are 8 DIMM slots on the motherboard and memory on all O2s is expandable to 1 GB using proprietary 239-pin SDRAM DIMMs
The O2 carries an UltraWide SCSI drive subsystem (Adaptec 7880). Older O2's generally have 4x speed Toshiba CD-ROMs, but any Toshiba SCSI CD-ROM can be used. The R5000/RM7000 units have two available drive sleds for SCA
UltraWide SCSI hard-disks. Because the R10000/R12000 CPU module has a much higher cooling-fan assembly, the R10000/R12000 units have room for only one drive-sled.
Networking is provided through an integrated 10/100 Base-T ethernet port.
- The CRM chipset that SGI developed for the O2, shares OpenGL calculations between CPU and chip. Due to the unified memory architecture, framebuffer memory comes from main memory, and there is effectively an 'unlimited' amount of texture memory.
- VICE (Video Image Compression Engine) accelerator
- OpenGL 1.1 + ARB image extensions.
Several operating systems
support the O2.
- IRIX 6.3 or 6.5.x (native platform).
- Linux port is working, but some drivers are missing. Both Gentoo and Debian have releases that work on the O2. See the IP32 port page on linux-mips.org.
- OpenBSD has run on the O2 since OpenBSD 3.7. See the sgi port page.
- NetBSD has run on the O2 since NetBSD 2.0. See the sgimips port page.
The SGI O2 has built in hardware for handling streaming media and still images, named ICE (Image Compression Engine). ICE consists of two parts: 66 MHz 64-bit R4000-derived control logic unit plus a 66 MHz SIMD
128-bit central processing unit. This unit is integer only, but still provides a significant amount of computational power which enables the O2 to do video decoding and audio tasks that would require a much faster CPU if done in software. Currently this unit works only with the IRIX operating system, as this is the only system that has drivers capable of taking advantage of this device.
The Unified Memory Architecture means that the O2 uses main memory for graphics textures, making texturing polygons and other graphics elements trivial. Instead of transferring textures over a bus to the graphics subsystem, the O2 passes a pointer to the texture in main memory which is then accessed by the graphics hardware. This makes using large textures easy, and even makes using streaming video as a texture possible.
Since the CPU performs many of geometry calculations, using a faster CPU will increase the speed of a geometry-limited application. The O2's graphics is known to have slower rasterization speed than the Indigo2's Maximum IMPACT graphics boards, though the Maximum IMPACT graphics is limited to 4 MB of texture memory, which can result in thrashing, whereas the O2 is limited only by available memory.
While CPU frequencies of 180 to 300 MHz seem low today, when the O2 was released in 1996, these speeds were on par with or above the current offerings for the x86 family of computers (cf. Intel's Pentium and AMD's K5). Further, the above listed features made it an excellent graphics workstation which was the market it was targeted at. It was however, even with the speed upgrades it consequently received, not able to keep up with the mainstream PC market and cheaper x86 based computers started to outperform it by the end of its lifetime.
- Imaging (especially medical)
- On-air TV graphics
- Desktop workstation
- 3D modelling
- Analogue video post-production
- Defense industries
In the web-comic Userfriendly
, the computer AI
'Erwin' is in the body of an SGI O2.
The SGI O2 computer is used to create the Local Forecast On The 8s for The Weather Channel, in their Weather STAR XL computers.