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R > RAIR MICROCOMPUTER > Business Computer   

RAIR microcomputer
Business Computer

The RAIR Business Computer is an obscure system since nearly nothing can be found on the net about it (apart from here :-))

The Business Computer is a multipost system. It can control/serve up to 4 attached terminal stations via RS422 connectors.

Its main particularity is to mix two technologies: 8-bit with its Intel 8085 CPU and 16-bit with its Intel 8088 CPU. Thus it can run CP/M, MP/M and PC-DOS software with no problem (according to the advert).

For mass storage, the system is equiped with a 19 MB Winchester hard-disk (up to 4 can be mounted) and a 5.25'' 1 MB floppy drive.


Lots of interesting information from Tim Hill
I managed the design of this system and was responsible for most of the OS software. Hardware design was by Dick Akers and Bob Marsh (of Processor Technology fame). Industrial design was by Mike Nutall (now in ID3) and for the time was pretty "wow" (most of the competition was sheet metal). The main unit was based on a RAIR Black Box but included two new features: a dual-CPU processor card (8085 and 8088) and a console card capable of driving four "consoles".

The dual-cpu card could only run one processor at a time; they switched back-and-forth under a software controlled dance. The 8088 was the main CPU, with the 8085 kicked in to run legacy 8-bit software (of which there was a lot at that time). Later units replaced this board with an early 80286 cpu card and running 8-bit software was handled by an emulator (written by me) -- not as crazy as it sounds as in fact it was *faster* than the hardware 8085! The display card was probably the most interesting part. The single card contained a dedicated 8085 cpu with enough muscle (for then!) to drive 4 color displays and handle keyboard input. This allowed the system to run 4 console sessions at once, even though each "console" was actually just a CRT and dumb keyboard.

The OS was MP/M-86, which could run the 4 consoles simultaneously. Native 16-bit CP/M programs ran directly. To run an 8-bit program, a tool called RUN85 was used which created a virtual 8-bit CP/M environment (easy since the two OSes were very similar) and then handed off to the 8-bit CPU for a time-slice. In addition, a purely software based MSDOS emulation facility allowed the "new" programs written for MSDOS to run as well; all of these at the same time just by running an application. Quite advanced for its time.

The achilles heel of the system was the slow performance of the display card (the 8085 really had trouble keeping up with the main system) and the lack of software that could support the (for the time) spiffy color display output. Overall, though, the system was well engineered and in some ways way ahead of its time.

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.).


Well, well, this is so 1980ties, the good old days when everything sold. The RAIR BC was a great idea which competed with color-screen but no graphic against the early PC graphic. The Display was just a line-display terminal. It was pretty slow but sold well in Germany, but nowhere else. Especially it was OEMed to Pitney Bowes who sold the machines under their own name. I believe over 2000 units were sold during a few years. This was a big number then. The machines died quickly from power supply problems and heat. I remember we even ran them in heat room for 72 hours to ensure that the machine survives.

Thursday 7th April 2011
Guenter H Krauss (Germany)

Hello, RAIR$DTI Team it gas great time working with you all $ i have learned so much. if any one looking for prototype work i am still available. thank You

Tuesday 14th February 2023
manisha andpragnesh patel (United States)

At Rothmans cigarette company we sought to use RAIR computers to distribute our computer systems from a central mainframe to local operations in factories, warehouses and offices around the UK.

We took delivery of the first off the production line around 1981 and had only a few models for software development at first.

We found that the machines were not powerful enough to do the jobs we had planned for them and had to change from distributed micro computers from RAIR
to distributed midi computers from ICL and later IBM.

Monday 17th February 2020
David Evershed (UK)


NAME  Business Computer
MANUFACTURER  RAIR microcomputer
TYPE  Professional Computer
YEAR  ? 1983
KEYBOARD  Full stroke keyboard, 83 keys, 10 programmable function keys, numeric keypad
CPU  16-bit Intel 8088 & 8-bit Intel 8085
RAM  256 KB (1 MB max.)
TEXT MODES  80 x 25 characters
GRAPHIC MODES  high resolution ?
SOUND  Unknown
SIZE / WEIGHT  Unknown
I/O PORTS  4 x terminal connectors (RS 422 compatible), 2 x RS232 ports
BUILT IN MEDIA  19 MB Winchester hard-disk + 1 MB 5.25'' floppy disk drive
POWER SUPPLY  Built-in power supply
PERIPHERALS  up to 4 additional hard-disks, magnetic tape drive, bidirectional printer (160 c/s)
PRICE  Unknown

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