RM Nimbus

The RM Nimbus system was a propitiatory system developed by the UK company Research Machines aimed mainly at the UK schools market. It could be as simple as a single stand along workstation, or a complex network, or multiple machines all running their own propitiatory software - or modified software from other software houses.

Nimbus Network

A normal nimbus network was a collection of workstations, and one or more servers. The original system was developed with the Nimbus AX as the server and the Nimbus PC-186 as the workstation, or print server. Later on the VX series was introduced as a replacement for the AX server, and the PC-286 and PC-386 workstations were produced. AX or VX machines could also operate as workstations if required, but as costs were prohibitive in most cases except were a AX server was replaced by a VX, allowing the AX to be put into use as a workstation.

The server would act as both a netowrk boot server, file serer and print server. Any type of nimbus machine (usually a PC-186) could in addition be added to act as a dedicated print server, however all print jobs were still routed via the main server and then the jobs copied as files from the server to the print server over the network. This in theory prevented the server from having to copy data to the parallel port and freeing up CPU cycles for other tasks, however it also put more data onto the network bus. It was however more helpful if two (usually one color and one black and white) were needed as the original AX/VX machines only had one parallel post and serial printing was rapidly become non standard.

The network was connected via BNC cable with T-pieces and ran on Zilog's Z-Net system. It allowed upto 127 workstations to be connected and booted directly from the netowrk server. A complex user log-on system - with significant vulnerabilities - was implemented allowing multiple user groups and for each group to be assigned a different menu structure in the original user interface, or different Program Managed windows in the later Windows 3.0 interface.

Most workstations were also equipped with a Piconet port but this rapidly became redundant due to the higher speeds with Z-net

Nimbus PC-186

The RM Nimbus PC-186 was a 16-bit microcomputer produced by Research Machines Limited in Oxford, England, during the mid-1980s.^[1]

It was developed as the original workstation for the nimbus network system, and ran a modified version of MS-DOS, and in its native form was not 100% IBM PC compatible, requiring the use of the 'SETMODE.com' application to switch between RM mode and PC code. It was replaced towards the end of the life of the nimbus system with the PC-286 and PC-386 workstations, both of which were 100% PC compatible

In most nimbus systems the 186 workstations were disk-less, with some having a single floppy drive. Sand alone workstations were also made -most with either twin floppy drives, or a 20Mbyte hard drive and single floppy drive.

I/O Connectors

Mouse - 9 pin D-Sub connector with pins wired in a different configuration to a standard 9-pin serial port Keyboard - Earlier modles- Standard AT keyboard port, Later modles -PS/2 keyboard port Video - 5 pin DIN plug with TTL RGB output compatible with BBC micro monitor connectors - modified CGA output Parallel - Optional via expansion card - usualy with BBC micro 'user port' along side- both with ribbon pin connectors Network -BNC connector - Zilog Z-NET, Ethernet expansion cards were available for later models - Both allowed netowrk boot Power - Standard IEC connector in and out for monitor supply

RM AX/VX

Both of these systems were used a servers for the Nimbus Network, or could be used as more powerful standalone workstations. The employed either EGA or VGA graphics cards, and were equipped with an ESDI interface for a harddrive, as well as a 3 1/2HDDD floppy drive.

There were listed as 100% PC compatable, but again only when XMODE was used to select PC mode.

By default they were equipted with a Z-Net inteface card, but a second Ethernet card could be added along side to allow both netowrk interfaces to be used simultaniously, however they would not bridge the two network interfaces.

PC-286 and PC-386

References