SGI Onyx

 General Information


The SGI Onyx really is has been introduced in 1993 and is still a powerful graphics server available as deskside systems or even rack systems. The deskside Onyx systems already can have up to four CPUs and four rastermanagers and thus are still nice machines for some serious work.

Processor Options

There are four processor families available for the Onyx: The R4400, R8000 and R10000. One CPU board can hold up to four R4400 or R10000 and up to two R8000. Of course you cannot mix CPUs.

Processor Board CPUs / Board Speed L2 Cache / CPU
R4400 IP19 1,2 or 4 100 Mhz
150 Mhz
200 Mhz
250 Mhz
1MB or 4MB
R8000 IP21 1 or 2 75 Mhz
90 Mhz
R10000 IP25 1,2 or 4 195 Mhz 1MB or 2MB

A deskside Onyx can hold only one CPU board (that is up to 4 CPUs) while a rackmount Onyx can hold up to 6 boards, which makes a total of 24 CPUs.


As most SGI systems, the Onyx uses proprietary memory modules, patented design by Silicon Graphics. Multiple third parties have been licensed to manufacture these memory modules.

The modules have 200 pins and provide 144 bits of data, including bits used for ECC. They are available in 16 MB, 64 MB and 256 MB sizes.

The memory board MC3 has four banks with 8 slots for each bank, that makes a total of 32 memory slots per MC3.

Graphic Options

Extreme Graphics

You can use an ExtremeGraphics option with an Onyx, but this is just not the idea of an Onyx.


Name Function
GE10V Geometrie Engine with 6 Intel i860XP
DG2 Display Generator
RM4 or RM5 Raster Manager; The RM4 has 4MB texture memory, while RM5 has 16MB, both have 40MB for frame buffer.

VTX really is nothing else than a downgraded Reality Engine 2 as you can see below. VTX only allows for one raster manager instead for up to four and has only half the geometry processing power.

Reality Engine 2

Name Function
GE10V Geometrie Engine with 12 Intel i860XP
DG2 Display Generator
RM4 or RM5 Raster Manager; The RM4 has 4MB texture memory, while RM5 has 16MB. Each Graphics pipe can have either 1,2 or 4 raster managers. But note that the amount of available texture memory will not increase with additional raster managers, as they work in parallel. But the amount of frame buffer memory increases by 40MB with each raster manager.


Infinite Reality

The System Bus

The main System bus is called PowerPath-2 and allows transfers up to 1.2GB per second. But there are also two other busses available for additional extensions and options. The backplane of a deskside Onyx has the following allocation:

Slot Name Function
1 MC3 Memory Board
2 CPU CPU Board
3 IO4B IO Controller
4 VCAM or GCAM VME or Graphics Bridge
6 VME VME64 or Extreme Graphics
7 VME VME64 or Extreme Graphics
8 GE Geometrie Engine
9 DG Display Generator
10 RM Raster Manager
11 RM Raster Manager (optional)
12 RM Raster Manager (optional)
13 RM Raster Manager (optional)

And the backplane of a rack Onyx has the following layout:

Slot Name Function
1 CPU or IMB or PC2  
2 CPU or IMB  
3 CPU or IMB or PC2  
4 CPU or IMB  
5 CPU or IMB or PC2  
6 CPU or IMB  
7 CPU or IMB or PC2  
8 CPU or IMB  
9 CPU or IMB or PC2  
10 CPU or IMB  
11 PC2  
12 VME VME64
13 VME VME64
14 VME VME64
15 GE Geometrie Engine
16 DG Display Generator
17 RM Raster Manager
18 RM Raster Manager (optional)
19 RM Raster Manager (optional)
20 RM Raster Manager (optional)


The VME64 Bus

The VME64 slots available in the Onyx and Challenge systems are the same physical size as those found in other IRIS systems. However, they have additional data signals making the data bus 64 bits wide. These slots do not support VSB connections.

Note that VME cards for SGI systems do not require front panels. Front panels are normally required for EMI sealing and connector mounting. Since the Onyx VME rely on the I/O Panel for EMI sealing, front panels are necessary. In fact, installing a 6U card with a front panel directly into the backplane will almost certainly cause the front panel to short out against any card in the slot to the right of the board.


The IBUS is the connection that is available on the IO4 board. Silicon Graphics makes several “mezzanine” boards available that use this interface. An example is the Audio/Serial Option (ASO) board. Due to the complexity and cost of design this bus is not generally available for developers for design purposes.


Here you can see the frontplane of the Onyx RealiytEngine with all connectors - click on the image for a bigger version. As you can see, there are really plenty of them, but unfortunately the Onyx has no Sound per default.

The Onyx has three RS232 plus one RS422 9pin serial ports. There is also a 25pin DB25 unidirectional parallel port.

There are also two SCSI-2 channels, one wide single ended and one wide differential SCSI channel. You can chose for each internal drive to which channel it should be connected to. Both the single ended and differential types of SCSI-2 connections use the same 68 pin connector, but the pinouts are slightly different.

Onyx Keyboard and mouse

An annoying problem is that Onyx don't have PS/2 compatible keyobards and mice, although the connector looks like it. Luckily it uses the same keyboard and mosue as Indigos, so if you can get one you can also use it for your Onyx. If you don't have a keyboard or mouse, maybe you can build yourself a converter. See this page for a description.

System Controller

The system controller monitors various system data (fan speed, temperature, voltages) and can initiate a controlled shutdown if any of these values exceeds given ranges. It is battery-backed and records error messages in case of any unplanned shutdown of the system. On both Deskside and Rackmount systems the system controller can be accessed without problems from the front of the machine.

Video Options

Other Options

My Hardware

See my SGI Onyx RealityEngine².