RM Nimbus - Facts

The Nimbus plastic cases were produced by Hallam Plastics which was in operation from 1971 to 2017

The 186 Nimbus monitor was a rebranded Mitsubishi XC-1404CB with alternate plug

The Early Nimbus Network was based upon Microsoft MS-Net Server

The original Nimbus 186 used the XT scancode with 84 keys, although one of them was unmarked and gives no data output, so its an 83 key. The keyboard also doesn't produce its own clock signal like a normal XT but instead works on 9600 baud.

The FDD & HDD controller in the 186 Pn 12865 was only fully populated if a HDD was fitted

The standard 196kb, PC-186 memory could be upgraded with the addition of an add-on board populated with HM50256P-15 chips. Space for 32 IC's. The first 16 gave the Nimbus an extra 512kb of memory. The next 16 allowed the use of the 511k RAMDISK software from RM.

The Nimbus 186 used a special version of MS-DOS 3.10 (or 3.05 on very early versions - 3.05 was actually MS-DOS 3.00 but for OEM's). Other versions would not work.

The Nimbus PC-186 used a General Instrument AY-3-8910 Music Chip

The Nimbus range was the last in-house hardware design by Research Machines, subsequent hardware was outsourced.

Windows 3.00 included special versions of Program Manager(progmanr.exe) which prevented end users from moving icons and program groups about on the Windows desktop.

The original Nimbus PC used a mouse in simlar design to the Bus Mouse, where no conversion to serial was carried out in the mouse, instead a quadrature signal was sent directly for movement and mouse buttons had a dedicated pin.