** External 5.25" FDD unit Connector Card
** Hard drive / Floppy Disk Controller Card
** Data Communications Card ([https://www.thenimbus.co.uk/nimbus-parts-list/DCCDCC])
** Parallel I/O Port Connector Card along with +5V and +12V output jacks
* IBM Utility Board Card - Fitted without the 8087 Maths Coprocessor, uses SP675 battery