The Octane, known also as IP30 or internally as the Speedracer or simply Racer, was a high-end graphics workstation manufactured from 1997 until 2000. From 2000 to 2004 a newer version was available (Octane2), which shares most of the architectural features with its predecessor. The Octane2 is not yet supported by Linux (mostly because there is no test hardware).
Its distinct green, squat, somewhat blobby shape is instantly recognizable as a Silicon Graphics machine.
An Octane is astonishingly modular. All parts of the machine can be separated easily and reassembled without hassle. This feature is well reflected in its architectural makeup. (All Octane modules are uniquely identified thanks to embedded 1-wire NICs.)
Unlike most other systems (based on bus topologies), the Octane uses a star routing topology between its devices. This idea was borrowed from Origin systems. Even the XIO bus is compatible between IP27 and IP30. The server heritage of this architecture allowed Octane to surpass competition in all bandwidth benchmarks.
The switch, which takes care of connecting correct XIO ports, is known as the XBow. It is located on the Octane frontplane (FP1).
All other devices, including the system module (the IP30 proper) are slid into the chassis from back and make their contact with the frontplane by way of the compression connectors (extremely fragile high frequency interconnect system). The Octane possesses four standard XIO slots (for up to four XIO cards), an atypical XIO slot designed for a PCI cage, and a dual XIO slot, into which the system module is inserted. It is also possible for a XIO card to occupy more than one XIO slot, however even then they use only one of the connectors.
One of the system module XIO connectors is designated as HEART. This is the main system ASIC, which integrates a XIO widget, a SDRAM memory controller (8 nonstandard DIMMs) and a 64-bit SysAD bus controller that can service up to four R10000, R12000 or R14000 processors. For some reason, SGI hasn't made a four-processor Octane so there are only one- and two-processor modules available.
The other system module XIO connector is occupied by a BRIDGE. This remarkable chip is able to efficiently connect up to 8 PCI devices to a XIO bus. (For that matter, a BRIDGE can also serve as a GIO master, although there are no known examples of such usage.) On the IP30 system board the BRIDGE is used to connect four PCI devices, the system Flash and the power button to the XIO fabric.
The first two of these devices are QLogic QL1040B Fast Wide SCSI controllers. One of them is devoted to servicing up to 3 internal hard disks (or other 3.5" devices, like streamers) mounted in special sleds in a front drive bay. The other one is available for connecting up to 15 external SCSI devices.
The third device is an IOC3, an I/O controller, which provides the Octane with most of its connectivity. Mouse, keyboard, two serial ports, a parallel port, Fast Ethernet and even the two system LEDs (white - which is a pair of lightbulbs in original Octane systems but is often changed to a pair of LEDs after the lightbulb burns out and red - which stays usually the original red LED) are all serviced by the IOC3 and its connected SuperIO chip. The hardware voltage sensors and the DS1687 RTC (Real Time Clock) are also hooked up to the IOC3 byte-wide expansion bus.
Fourth of built-in PCI devices, the RAD1, is a no-frills audio system. Although it does not possess any processing capabilities (it is basically just a DMA chip), its general quality is undeniable. It sports both S/P-DIF (or AES/EBU), ADAT (8-channel 24-bit sound) and decent analog I/O. It is also capable of writing exact timestamps.
The Octane can be equipped with one of two graphics families. The older one is IMPACT, that is inherited from the Indigo2 workstation series. These are the SI, SI+T, SSI, MXI cards and their updated (and accelerated) versions ESI, ESI+T, ESSI and EMXI (also known as SE, SE+T, SSE and MXE). The S?+T and MX? cards contain texture modules that allow the Octane to do hardware texturing. Support for the IMPACT series is available in the Speedracer Linux kernel.
Newer Octanes and all Octane2s contain the ODYSSEY series graphics. These cards, known as VPro, are integrated single-chip solutions. They come in four versions: V6, V8, V10 and V12. None is supported because of lack of test hardware and information. The ODYSSEY series graphics is also used in Tezro machines.
A second graphics card can be inserted into any of the free XIO slots.
A PCI cage can be slid into a specially shaped XIO slot. The cage contains a BRIDGE chip and three 64-bit PCI sockets (one of the cards has to be shorter because of the mechanical constraints). From programmer's point of view, there is no difference between the system board BRIDGE and the PCI cage one.
There are also quad and single Fast Ethernet XIO cards (MENET - they contain a BRIDGE and four IOC3s), a Gigabit Ethernet XIO card, XIO horseshoes (a mini-cage for a single PCI card) and a very mysterious XIO Tensor Processing Unit (TPU) of which not a single piece was ever seen (which naturally makes it interesting). None of them (except maybe MENET) are supported.