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I > ICL  > Quattro   


With the Quattro, ICL attempted to tackle the multi-user market which was still opened with neither definitive system nor operating system.

The Quattro was a development of earlier ICL Personal Computer which in turn was a development of the Rair Black Box

The machine was named Quattro as it supported up to four users, each user running up to four programs simultaneously.

Internal hardware design was quite similar as the Personal Computer's. An eight connector backplane supporting logic boards. However, the CPU board featured a 16 bit 8086-2 and up to 1 MB of RAM could be installed.

Thre models were available:
Model 19 with 256 KB RAM and 2 x 5" 800 KB floppy drive,
Model 39 with 512 KB of RAM, one floppy drive and one 10 MB hard disk,
Model 49 same as Model 39 but with a 20 MB hard disk.

The Quattro could work with wirtually any video terminal. ICL supplied its own monochrome (6402G) and colour (6404G) graphic versions along with a 102 key keyboard.

It was delivered with Concurrent CP/M Operating System, later called Concurrent DOS, a true multi-tasking, multi-user O.S. which offered a very limited compatibility with MS-DOS.
Sadly, few major software of the time, running on the first IBM PC and clones, were adapted to the specific features of the ICL. This is the main reason why the Quattro didn't meet any success, except near some corporate customers who already used ICL mainframes.

We need more info about this computer ! If you designed, used, or have more info about this system, please send us pictures or anything you might find useful.
Please consider donating your old computer / videogame system to or one of our partners from anywhere in the world (Europe, America, Asia, etc.).


George, the Disc A Hung wasn''t a hardware fault - it was a race condition in the hard disc controller code. I''ll never forget that bug, it took me 18 months on-and-off to fix the b****y thing. No matter how hard we worked the system it wouldn''t fail. It turned out you had to work the CPU hard, and the disc hardly at all to make it happen.
And the fix was to swap to adjacent sections of code, one 3 lines and one four.

Friday 21st March 2014
Andy C

I worked for the IT department of the UK Home Office. We had quite a few systems running on these machines. The ones I was involved with were for the centres that maintained and repaired radio equipment for the Police and Fire Brigades.
I wrote a system using the Dataflex 4GL system to track repairs through the workshops - up to 4 terminals, some in the stores, others in the workshops.
I do remember having to write a small assembler program to allow the users to enter the system date in UK format on startup (the clock was not battery backed), as these were really rebadged Rair machines, which expected data entry in US format.

Friday 4th January 2013
Chris Quinn (Liverpool, UK)

I worked for a computer dealer which sold these to run our proprietary accounting software. There was a problem whereby, seemingly at random, the machine would freeze with a "Disk A hung" message (Disk A being the hard disk). ICL eventually acknowledged this as a hardware problem although, by then, our small number of ICL customers had been moved to other systems due to their unreliability.

Our software was written in MS Basic and I spend two weeks converting it it to CBasic - only for an MS-DOS emulator to appear which ran the MS-DOS versions of our programs substantially faster than the native CBasic ones.

The OS, Concurrent CP/M, didn''t have tree-structured directories, it had numbered areas on the disk, 0 - 15.

Friday 11th June 2010
George Morrison (UK)


NAME  Quattro
TYPE  Professional Computer
ORIGIN  United Kingdom
YEAR  1985
KEYBOARD  Full stroke 102 key with function and arrow keys and numeric keypad
CPU  8086-2
CO-PROCESSOR  Socket for 8087 math coprocessor
RAM  From 128 KB to 1 MB
ROM  40 KB
TEXT MODES  80 chars x 25 lines
GRAPHIC MODES  640 x 400 dots (ICL terminals)
COLORS  Monochrome or 8 colours
SOUND  Beeper
SIZE / WEIGHT  Unknown
I/O PORTS  6 x serial RS232 ports, custom serial port, RS422 port, RGB port
BUILT IN MEDIA  1 or 2 x 5.25'' 800 KB floppy drives, 10 or 20 MB hard disk
OS  Concurrent CP/M V.3.1
POWER SUPPLY  Built in switching power supply unit
PERIPHERALS  RAM expansion, 2nd 20 MB hard disk, ICL monitors and printers
PRICE  Model 19: £2195 - Model 39: £4395 - Model 49: £4995
Monochrome terminal: £899 - Colour: £1399

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