Professional Iris



The Professional Iris line was introduced by Silicon Graphics in the mid 1980s as a successor to the IRIS 3000 line.

Like other workstation manufacturers during that period SGI did jump on the RISC bandwagon. The Professional Iris systems are the first SGI computers based on the MIPS RISC processor.

The following is a press release announcing the 4D/60:

Silicon Graphics Inc introduces the new Iris-4D workstation. 

The first member of the Iris line is the 4D/60, a RISC superworkstation with a 32-bit 
8 MHz CPU from MIPS Computer Systems. It offer performance three times that of the 
Silicon Graphics Iris 3100 series. The graphics performance has been enhanced with 38 
custom and semicustom graphic chips. It performs 140,000 32 bit three dimensional 
floating point transformations per second and renders over 4,500 100-pixel polygons 
per second with smooth shading and hidden surface removal. It offers 24 colour bit-planes 
for more than 16illion colours; four user-accessible system planes for overlay or 
underlay, menu and windowing functions; a 24-bit Z-buffer enabling hidden surface removal 
with greater accuracy and realism; high-level primitives such as splines and surfaces 
for more accurate renderings; and a multi-mode graphics windowing environment. 

Standard configuration includes 4Mb CPU, eight colour bit-planes for 256 colours); 
four system planes, a Weitek-based floating point accelerator board; a 170Mb ESDI 
disk and controller; a 19″ 1,280 by 1,024 60Hz non-interlaced colour monitor; keyboard 
and mouse; and a floor-standing chassis with 12 VME slots and a 1,000-watt power supply. 

Software compatible with the previous generation, it runs Unix System V.3 with a base 
price of $74,000.

The following benchmark ratings are taken from old comparison tables posted in comp.benchmarks:

          4D/60     4D/50      4D/70     4D/80     4D/85
MIPS -- 7 10 13 --
MFLOPS -- -- -- -- --

The successors of the Professional Iris line were the Personal Iris workstation and the more powerful Power Series visualization systems and servers.


Model CPU board CPU Chassis
4D/60 R2300 MIPS R2000 8 MHz Twin Tower
4D/50 IP4 MIPS R2000 8 MHz Twin Tower
4D/70 IP4 MIPS R2000 12.5 MHz Twin Tower
4D/80 IP4.5 MIPS R2000 16.7 MHz Twin Tower
4D/85 IP4.5 MIPS R2000 16.7 MHz Single Tower

The 4D/70 was also referred to as 4D/60T or 4D/60 Turbo.


March 1987
4D/60 announced
4D/50 announced as successor to 4D/60 for low-end workstation market
November 1987
4D/70 announced
4D/80 announced as successor to the 4D/70 systems
4D/85 announced


The following table includes a list of CPU boads used in the different Professional Iris workstations:

CPU Board Processor Clockspeed Cache (d/i) Cache (2nd) Floating Point
R2300 R2000 8 MHz 32kb / 64kb none R2360 FPA board
IP4 R2000 8 MHz 32kb / 64kb none R2010 onboard
IP4 R2000 12.5 MHz 32kb / 64kb none R2010 onboard
IP4.5 R2000 16.7 MHz 32kb / 64kb none R2010 onboard


R2300 Boards

Unlike the IP4 and IP4.5 boards the R2300 did not support onboard memory. Memory was added using separate 4 mb memory boards. The maximum configuration includes 3 of these additional boards for a total of 12 MB memory.

IP4 Boards

The memory configuration on IP4 boards is as follows:

Type:                   standard 30pin 9chip SIMMs
Sockets:                8

Minimum configuration:  8 MB
Maximum configuration:  16 MB

IP4.5 Boards

The memory configuration on IP4.5 boards is as follows:

Type:                   standard 30pin 9chip SIMMs
Sockets:                8

Minimum configuration:  8 MB
Maximum configuration:  16 MB

In addition to that it was possible to add additional memory boards to a 4D/8x system to obtain a maximum of 144 MB per system. The boards were H4R-C16 (16 MB) and H4R-C32 (32 MB) and could only be used, if the CPU board itself was populated with 16 MB.


Two groups of graphics options had been available for the Professional Iris. The Clover 1 family (G) and the Clover 2 family (GT).

Apparently Clover 1 graphics subsystems were common on 4D/50, 4D/60 and 4D/70 systems while Clover 2 was usually found in the newer 4D/70, 4D/80 and 4D/85.


Standard Input Devices

The keyboards and mouse for this system are of the proprietary IRIS4D type. The mouse can be connected to either side of the keyboard which is attached to the workstation using the connector on the other side. The mouse is of the optical type that requires a metal sheet with a raster printed on it to operate.


Typically SCSI drives are used with Professional Iris systems. Common were 5.25" harddrives as well as QIC-120 tape drives.


The classic twin tower enclosure has on the back of the bigger tower the following connectors:

  • 4 serial ports (DB9)
  • keyboard (DB15)
  • 2 powered peripheral ports
  • AUI ethernet

Other connectors are present depending on the options installed (SCSI Centronics, ESDI interface, RGB BNC).


Network Options

  • Ethernet

Video Options

Misc Options

  • 6port serial card
  • ESDI controller


Twin Tower


The Professional Iris systems traditionally came usually in a twin tower chassis (12-Slot Twin Tower).

The big "half" houses the boards of the system and has all the external connectors on its back, the small "half" is the drive tower for the internal drives.

width:     60 cm / 23" (estimated)
height:    66 cm / 26"
depth:     69 cm / 27"

weight:    unknown

Backplane Layout

01 CPU This slot is for the CPU/Memory board which MUST sit in slot #1!
02 VME The VME Slots have to be filled from left with no empty slots in-between.
03 VME
04 VME
05 VME
06 VME
07 VME
08 GFX How the graphics slots are used depends on the graphics option installed. They spaces between them differ a bit to accomodate for the G (Clover 1) boardset.
09 GFX
10 GFX
11 GFX
12 GFX

The type of the graphics option installed (at the time the system was shipped) is indicated by the color of top of the two towers. B and G graphics machines had purple, GT machines teal and server systems beige top hats.

Single Tower


There is not much known about the single tower Professional Iris systems except that this chassis must have been introduced with the later systems (4D/85 and maybe 4D/80). There is no further information on what type of backplane they use and how interchangeable the parts between old single and the new twin tower is.


Rebadged Systems

Professional Irises were at least sold also by Prime Computers and Control Data (according to the This Old SGI FAQ). There is no indication if other companies that used to sell relabeled systems (like Siemens) did also sell this first IRIS 4Ds. What the Control Data system looks like is unknown but the Prime machines were white and had always red top hats.


Operating System

Choosing an operating system.

The Professional Iris line of MIPS based computers are the first to run IRIX which was called 4D1 back then.

Details on the early IRIX versions are very vague so it is not possible to say which the earliest version is that can be run on a specific system. Support for the Professional Iris is in all 4D1-3.x versions, possibly varying degree.

The Professional Iris is also supported in the all platform versions of 4D1-4.x and IRIX 5.x. With the exception of the support of the Clover 1 G graphics option which ended after 4D1-4.0.5 all Professional Iris models can run up to IRIX 5.3.

Circuit Breaker

Signs of failure: When the cardcage is open the systems circuit breaker is activated.

On Professional Iris Twin Tower and possibly also Single Tower systems there is a small switch which is used to check if the cardcage door is closed. It is not intended that the system is powered up with the door open. Later SGI systems do not keep the owner from powering up the system while the cardcage is still open.

The switch is pushed when the center screw on the top of the door is locked, it is released when the door is open. If the system is powered on while this switch is in the open state the main circuit breaker on the powersupply is tripped. Nothing else happens. The small switch can be pushed by using the screw from the door whil the latter one is still open.

Keep in mind to check if there are no other reasons why the circuit breaker did trip. If it does while the small switch is pushed, there is good reason to check the system thouroughly for other problem.




Professional Iris with Prime skins.

CPU Boards

Professional Iris IP4 CPU board equipped with 4 SIMMs.

Clover 1 Graphics

Clover 1 GF3 board.

Clover 1 DE3 board.

Clover 1 TB2 board.

Clover 1 ZB2 Z-Buffer option board.

VME Options

VME Ethernet Option board.

CNC Ethernet

ESDI controller