The JMC On-Board Computer, also called the JMC Mainframe, was a silent, faceless and apparently non-sentient computer installed aboard Jupiter Mining Corporation spaceships.

Whereas most spaceships had artificially-intelligent computers (such as Holly, Gordon or Cassandra), the silent mainframes could run the ship if the intelligent computers were removed or broke down.


One such silent mainframe ran Red Dwarf in Holly's absence, communicating with the Boys from the Dwarf with internal printed mail, or "e-posts". (Series X)

Due to his actions of bravery which the on-board computer was told about by Kryten, it awarded Howard Rimmer the Platinum Star of Fortitude, the Space Corps highest military decoration, and even suggests that Red Dwarf be renamed the "SS Howard Rimmer" in his honour. This announcement by the JMC mainframe drove his jealous and envious brother Arnold Rimmer into another resentment overload. (RD: Trojan)

The Dwarfers tried to replace the silent mainframe computer with a sentient one named Pree, but this didn't go so well. (RD: Fathers & Suns)

Rimmer wrote many letters of recommendation to the JMC On-Board Computer pretending to be Admirals of the Space Corps, suggesting that Rimmer be promoted to Captain and awarded the "Golden Stripe of Honour". However, the JMC On-Board Computer did not fall for this, and requested in an ePost that Rimmer stop writing the letters. Instead, the JMC On-Board Computer noticed that Rimmer had not clocked in for Z Shift in over three million years since the accident, it threatened to legally demote Rimmer to Third Technician, the same rank as Lister.

Horrified, Rimmer was faced with losing his status as Second Technician and the highest ranking present crewmember. Rimmer ordered Kryten to help him find a solution, and although the mechanoid was unenthusiastic to help Rimmer, Kryten's programming forced him to follow orders. Kryten noted that there was an astonishing amount of unused toilet paper in the 2,143 restrooms of the ship, and there was very few "toilet-active crewmembers" aboard. They could remove this toilet paper, and channel the supply funds into the medical fund - effectively bribing the Medi-Bot for a sick note for Rimmer.

Lister wasn't keen on this idea, since he needed the paper due to his diet that was rich in "fiber, curry and beer". However, Kryten took a trolley round and gathered up the thousands of toilet rolls. The plan didn't work, since the Medi-Bot could not be bribed. Plan B worked when Rimmer instead achieved in getting a carer's note, when Lister was found apparently having sex with a vending machine. Rimmer convinced the JMC On-Board Computer that he had been looking after a mentally-unwell Lister. (RD: Dear Dave)


  • It is not made clear whether it was already installed when Red Dwarf left the Solar System, or was acquired from the many JMC derelicts they have come across over the years.
  • It is said that they've "made contact" with the JMC mainframe (in a similar manner to how Red Dwarf "made contact" with the All Droid Station); a strange way of wording it since the JMC mainframe is supposedly already on-board the ship. This perhaps suggests that the JMC mainframe that it is not on-board at all, but broadcast from somewhere else. If this conjecture is correct, the mainframe could be broadcast from the home of the JMC, Jupiter. If so it would mean that Red Dwarf is finally getting much closer to Earth's Solar System, proving that the JMC Mainframe is much more efficient than Holly, since Holly had apparently been making the ship going round in circles instead of it getting the ship back to Earth. (Queeg, Series II)

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