carenath: PERQ 3a

carenath was the first really interesting machine I obtained... carenath is an ICL 3300 Graphics Workstation, also known as a PERQ-3a. You can see my pathetic attempt at a PERQ-3 Trivial FAQ if you like. This is a Unix machine dating from about 1986. It's based on the 68020 processor, and it has the 68881 FPU and also some custom graphics hardware and a huge black and white monitor, as befits a graphics workstation... This machine was still being developed when Perq Systems went bust, so only 30 or so prototypes were ever made. I'm told mine is one of the later ones.

Although it is frequently referred to as a PERQ 3, the machine was in fact designed by ICL rather than PERQ Systems. ICL manufactured PERQ machines in the UK; they also had some input into the design, I believe. The 3a was all ICL, but my personal suspicion is that the plug was pulled on it partly because the death of Perq Systems would mean the loss of the American market and partly because the design of the machine is really nothing special.

I'd like to get carenath to talk to my PC somehow - it has an ethernet connection on the back, and a couple of serial ports. However, it doesn't speak TCP/IP. I may try to remedy this... I have produced some extremely hacked together scripts that use split and shar to transfer files from one machine to the other. I could be persuaded to part with them if you're really desperate :-)

I can't write anything to allow carenath to NFS mount Linux filesystems because I don't have source code to the OS (PNX 300 - an ICL variant of System V release 2) - does anybody? What carenath does have is a thing called the Newcastle Connection. I have user man pages, and this seems to allow use of remote filesystems and so on - however, I don't have enough technical information to implement this under Linux. If anybody does, please email me at!

In the long term, it would be interesting to see if I could use carenath as an X-terminal, taking advantage of its nice large monitor. I have no idea how hard this is going to be.
Unfortunately, I suspect that X really needs more memory, even if the only thing running is the X server. carenath has 2MB, which really isn't enough...
One workaround for this is to delegate some of the processing and memory requirements to my Linux box. The Linux box would essentially act as the X server as far as clients were concerned. It would simply pass on drawing requests to the PERQ. This setup relieves the PERQ of the necessity of storing information on the current state of the X server. Unfortunately, it probably increases the implementation difficulty still further...
Since I now have kuzuth, which has an even better display, this project has been cancelled :-)


I obtained carenath from somebody who I think was an ex-ICL employee. Certainly ICL sold the prototype systems to their employees; unfortunately they wiped the OS source code first...


Overall view

overall view
An overall view of system unit, monitor and keyboard.

Front of system unit

front of system unit
Front of the system unit, showing 5.25" disk drive (mounted vertically) and the Diagnostic Display System (7-segment LED display below the ICL logo).


The PERQ 3 mouse; note the odd shape. Its other distinguishing feature is a steel ball (not visible...)

Interior View

interior view
This image shows carenath lying on its side with the top and side plates removed. The lower half (in this orientation) is the memory and CPU boards; the protruding cable is the SCSI cable (unplugged from the OMTI board for clarity). In the upper half is the PSU (black metal box at the back, and also the hard disk (top left) and the floppy (bottom left) with the OMTI board (hard/floppy disk controller) mounted on top of the floppy drive.

Left Hand Side

left side
This is the left side of the system box (the upper side in the previous image), showing hard disk (bottom right), OMTI board with SCSI cable (top right) and PSU (left). The red bits on the left are warning labels over the mains inlet and the power on/off relay.

OMTI Board

OMTI Board
Closeup of the OMTI floppy/hard disk controller board. Connections to disks are on the left; the SCSI cable connector is on the PCB in the bottom left quadrant, vertically.

Memory Board

Memory Board
Overall view of the memory board; there are 2MB of combined system and video memory here.

CPU Board

I have some shots of the CPU board, but they aren't here yet; I haven't yet got round to putting the overlapping images together into a composite image...

This page written by Peter Maydell (