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. Graphics The O2 used the CRM chipset specifically developed by SGI for the O2. It was developed to be a low-cost implementation of the OpenGL 1.1 architecture with ARB image extensions in both software and hardware. The chipset consists of the microprocessor, and the ICE, MRE and Display ASICs. All display list and vertex processing, as well as the control of the MRE ASIC is performed by the microprocessor. The ICE ASIC performs the packaging and unpacking of pixels as well as operations on pixel data. The MRE ASIC performs rasterization and texture mapping. Due to the unified memory architecture, the texture and framebuffer memory comes from main memory, resulting in a system that has a variable amount of each memory. The Display Engine generates analog video signals from framebuffer data fetched from the memory for display. Operating systems 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 ran on the O2 starting from OpenBSD 3.7 until the discontinuation of the "sgi" port in OpenBSD 6.9. NetBSD has run on the O2 since NetBSD 2.0. It was the first Open Source operating system to be ported to the O2. See the sgimips port page. Performance The SGI O2 has an Imaging and Compression Engine (ICE) application-specific integrated circuit (ASIC) for processing streaming media and still images. ICE operates at 66 MHz and contains a R3000-derived microprocessor serving as the scalar unit to which a 128-bit SIMD unit is attached using the MIPS coprocessor interface. ICE operates on eight 16-bit or sixteen 8-bit integers, 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 without SIMD instructions. ICE only works 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