Version 3.00C
Early versions of the Nimbus PC featured 3 cartridge slots.
Details are a little sketchy and it appeared short lived, however details suggest 2 ROM slots and 1 software 'key' slot for protected software.
Advice coming in is that the ROM system was never put into full production, perhaps none were ever produced commercially?
However the softkey does look to have had some degree of implementation.

A ROM cartridge would allow for fast (read-only) access to an application. It has been suggested that this was developed for educational software use.

The Software Key looked to be an early adoption of a security dongle to protect software. Access to which was denied without the correct 'key'

The June 1986 Nimbus catalogue states:
Softkey is a specially designed software
key or dongle which will allow
developers to ensure protection of their
software copyright. The Softkey
contains a firmware code unique to the
user. The software contains the same
code and needs to be matched with the
softkey before it will run. In other
words, the licensed software can only be
run by a user in possession of the
appropriate unique softkey.

The cartridges looked to have a sliding mechanism, similar to a matchbox. Movement of which would expose the connection contacts.

The task of plugging and unplugging into the Nimbus mechanism would perform this action automatically one would assume.

The only known photo of a 'Softkey'

Example of the ROM cartridge

Showing the ROM Cartridge and the Software Key inserted

ROM Cartridges
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