Thursday, 12 August 2010

My first Home PC – recollections of the RM Nimbus PC-186

Despite having recently mentioned the Jupiter Ace and Sinclair Spectrum, early hobbyist computers, I am happy to admit to never owning either of those devices being far too impatient an individual to work with cassette tapes and the like. So I was never an early adopter of computers outside work and my personal home computer journey began in 1984.

The RM Nimbus PC-186 was released sometime in early 1985 - I recall demonstrating a beta-release of Windows (version 1) on the Nimbus to journalists visiting BETT 85 (British Educational Training and Technology Show). Incidentally BETT ( has grown to be the major annual event for information technology in UK Education, now occupying the huge Olympia exhibition centre in London for several days each January. But I digress.

Released just around the time that ‘IBM compatibility’ became fashionable for Personal Computer design, the Nimbus used an Intel Processor (80186) to run MS-DOS (3.x) but made no attempt to match the hardware compatibility points of an IBM PC. This was not unusual in the early 1980s; here in the UK, non-IBM-compatible MS-DOS computers from Apricot Computers were popular in some commercial sectors around the same time.

RM (then officially Research Machines Limited, was already established as one of the leading suppliers to UK education with the RM 380Z and 480Z computers, both 8 bit machines using CP/M with Z80 microprocessor. These were among the first small computers to make substantial use of networking; the 480Z was a very early example of a diskless workstation on a Local Area Network (LAN).

Working with RM at the time, I was fortunate to get my hands on one of the first batch of Nimbus prototypes in 1984 so my first home PC was this ugly but functional box with unfinished casework, an item for the study not the living room.

The Nimbus was the first 16 bit computer from RM. The combination of a faster processor than the IBM PC (8Mhz 80186 as against 4.77Mhz 8088), a larger maximum memory space (960K v 640K), and use of 3.5" 720Kb disks (v 5.25” 360Kb) raised some interest. A unique feature was ‘Piconet’, a serial interface for peripherals, a kind of early forerunner of USB, a good idea but before its time and let down by the performance of its implementation. My machine had a 10Mb hard drive, a luxury at a time when systems often had to make do with floppies or a LAN server. The Nimbus was a modest commercial success. I have no sales numbers to hand but certainly over 100K systems shipped to UK schools before RM adopted mainstream IBM compatible 286 then 386 based systems. The main competition in education was the Acorn/BBC microcomputer. Unlike the situation in North America, Apple never made much progress in the UK Education market largely due to high prices compared with Acorn and DOS based systems.

The Nimbus display was unique – a ‘high’ resolution graphics mode of 640x250 pixels with only 4 colours (black, white and a choice of the other two from the usual 14 suspects, I usually settled for red and blue). In modern terms that sounds like a nightmare. Indeed the reality was worse, just not quite so drab as the monochrome 640x200 (CGA) graphics used on the IBM PC or the 512x342 Apple Macintosh of the same era. A more colourful 320x250 display mode was used by most educational software for the Nimbus but I rarely used this 16-colour mode personally, my home computer activities largely involving software development, word processing and spread sheet applications. My campaign for usable graphics on personal computers was already underway by then but that is another story.

My software 1984/5. TXED, the RM full screen text editor, was useful. I created the Nimbus ports of Microsoft Word (for DOS) and Microsoft Multiplan (the DOS-based predecessor to Excel) for RM. This combination made for basic PC office productivity applications and it was bundled as such with a range of Nimbus configurations. For software development, I learned C and the new C++ programming language. However assembly language programming was still crucial for these low memory slow systems. My largest assembly project was an adaptation of Microsoft Windows 1.x to the Nimbus.

It is a reflection on the limited applications at that time I suppose that this development work was about the most entertaining aspect of home computing in my early personal experience. Fortunately for children and teachers in schools, there grew a useful and sometimes fun catalogue of educational software and simple games for the Nimbus.

After around 18 months with the Nimbus PC-186 as my home computer, I upgraded to an 80286 IBM compatible for most activities although my Nimbus hung around for several years (and several revisions of Windows up to and including the 1990 release 3.0).

An interesting footnote on those early years of software development for Microsoft Windows. Curiously enough, the extra memory available over the IBM PC architecture meant that Windows on the Nimbus had about twice the memory available for applications once DOS and Windows fixed overheads were taken into account. It took until 1988 and early alpha versions of Windows 3.0 to enable an IBM compatible to win out in the memory stakes.

No comments:

Post a Comment