SGI O2
| Company type | Public |
|---|---|
| Industry | Computer hardware |
| Founded | November 13, 1981 in Mountain View, California, United States |
| Founder | Jim Clark, Abbey Silverstone |
| Headquarters | Mountain View, California , United States |
| Products | Workstations, servers, software |
| Website | www |
The O2 workstation, introduced in 1996 by Silicon Graphics, Inc. (SGI), was designed as an entry-level Unix system intended to replace the Indy. Primarily aimed at multimedia use cases, it incorporates a single MIPS CPU and positions itself as a cost-effective alternative to SGI's more advanced SGI Octane line. The O2 marks SGI's last venture into the budget workstation segment.
System architecture
Initially referred to by the codename "Moosehead," the O2’s design utilizes a proprietary high-throughput Unified Memory Architecture (UMA) that interconnects system components seamlessly. A solitary PCI slot interfaces via this UMA. The chassis features a modular layout with a unique enclosure, supporting up to two SCSI drives mounted on dedicated caddies—although later R10000/R12000 variants are restricted to a single drive due to thermal considerations. An optional add-on module provides video capture and audio capabilities.
CPU
The O2 lineup includes two processor categories: entry-level configurations equipped with 180–350 MHz R5000 or RM7000 CPUs, and higher-performance models featuring 150–400 MHz R10000 or R12000 processors. It is noteworthy that 200 MHz R5000 chips with 1 MB of L2 cache outperform the earlier 180 MHz versions that have only 512 KB cache. Additionally, an enthusiast project has successfully installed a 600 MHz RM7xxx processor into an O2 system.
Memory
All O2 models come with eight DIMM slots compatible with up to 1 GB of proprietary 239-pin SDRAM modules. Memory management is handled by the Memory & Rendering Engine (MRE) ASIC, which operates over a 133 MHz, 144-bit wide bus—128 bits dedicated to data transfer and the remainder for ECC—linked through buffers to a 66 MHz, 256-bit memory subsystem.
I/O
Input/output operations are managed by the IO Engine ASIC, which provides a 64-bit PCI bus, an ISA bus, dual PS/2 port connections for keyboard and mouse, as well as a 10/100 Base-T Ethernet interface. The PCI bus consists of one 64-bit slot, while the ISA bus supports a Super I/O controller that offers serial and parallel port functionality.
Disks
The storage subsystem relies on an UltraWide SCSI controller (Adaptec 7880). Earlier units generally include Toshiba CD-ROM drives running at 4x speed and compatible with other Toshiba SCSI devices; however, IRIX supports only Toshiba CD-DA mode. Later releases are equipped with Toshiba DVD-ROMs. Models powered by R5000 or RM7000 CPUs can accommodate two drive sleds for SCA UltraWide SCSI hard drives, whereas R10000/R12000 versions are limited to one sled due to larger cooling fan requirements.
Graphics
The O2 utilizes SGI’s CRM graphics chipset, engineered to provide an economical hardware and software implementation of OpenGL 1.1 featuring ARB image extensions. This chipset comprises a microprocessor alongside ICE, MRE, and Display ASICs. The microprocessor manages all display list and vertex processing tasks and controls the MRE ASIC responsible for rasterization and texture mapping operations. The ICE ASIC handles pixel data formatting and manipulation. Thanks to the unified memory architecture, texture memory and framebuffer share the main system memory pool, allowing dynamic allocation between them. The Display Engine converts framebuffer contents into analog video output signals.
Operating systems
The SGI O2 supports a range of operating systems, including:
- IRIX versions 6.3 and 6.5.x, which serve as its native environment.
- Linux with limited driver compatibility; distributions such as Debian, Gentoo, and T2 Linux provide supported builds.
- OpenBSD was compatible from version 3.7 up until the "sgi" port was discontinued in version 6.9.
- NetBSD became the first open-source system to be ported to the O2 starting with release 2.0.
Performance
The SGI O2 features an Imaging and Compression Engine (ICE) ASIC running at 66 MHz, utilizing a microprocessor derived from the R3000 architecture alongside a 128-bit SIMD unit accessed through the MIPS coprocessor interface. This ICE chip efficiently handles eight 16-bit or sixteen 8-bit integer operations, facilitating video decoding and audio processing tasks that would otherwise demand higher CPU speeds. ICE capabilities are restricted to the IRIX platform due to exclusive driver support.
Owing to its Unified Memory Architecture, the O2 can directly access textures stored in main memory through pointers, which streamlines the handling of large textures and enables video streaming as textures without incurring bus transfer overhead.
Geometry computations rely heavily on CPU performance; therefore, applications limited by geometry benefit from faster processors. Although the O2’s rasterization throughput is slower compared to the Indigo2 equipped with Maximum IMPACT graphics boards—which possess limited texture memory—the O2’s texture capacity is only bounded by the total system memory available.
When introduced in 1996, its CPUs ranged from 180 to 400 MHz, placing them on par with contemporary x86 processors such as Intel’s Pentium and AMD’s K5.
Uses
Typical deployments of O2 workstations included:
- Medical imaging applications
- Real-time television graphics, particularly within the Weather Star XL system used by The Weather Channel
- Desktop computing environments
- Three-dimensional modeling
- Analog video post-production workflows
- Defense-related projects