As the identity of the AI I'm asking about is a major plot point in the game Halo: Reach and as I've just recently finished it, I've decided to keep the identity of the AI a secret using spoiler code in my question.

In the original Halo Trilogy Cortana is carried in a SD-like chip that fits into the back of the Master Chief's helmet. In Halo: Reach the player is given Cortana in a large canister that they attach to their lower back.

I know the Spartans in Halo: Reach are of the third generation of Spartans that were created and that the Master Chief is a second generation Spartan.

What is the in-universe explanation for the differences in their ability to carry AI? Do the third generation spartans have a different type of armor or were they securing the AI in that manner for another reason?

I've considered that perhaps the Master Chief only uses the chip because he's exiting the ship in an emergency setting and that maybe the canister is the standard way to move expensive starship class AI such as Cortana.

UPDATE - The Halo Wiki says that "[Noble] team was issued with the Mark V MJOLNIR armor on November 24, 2551." This is the same Armor Master Chief is equipped with in Halo: Combat Evolved.

"Reach takes place...during the year 2552".

The Mark V MJOLNIR page says that the armor has a "revolutionary crystalline layer forms a network, capable of supporting the kinds of artificial intelligence usually reserved for warships, on a piggyback system."

"The synthesis of an artificial intelligence with the human brain is not possible without an upgrade to the user's standard Neural Interface. This specialized version of the neural lace is issued to all SPARTAN-IIs before they can interface with the Mark V. Like the standard Neural Interface, the specialized neural lace translates electrochemical signals to digital code and routes them through an interface connection at the rear of the skull. Through this interface, the user's thoughts command the armor's movement and weapons; and input from the on board sensors comes directly to the user's mind. In addition, an AI personality and processing matrices can be carried by the armor and delivered to the suit via the specialized neural lace and on board storage in a crystal data chip no larger than a personal credit card. Without the armor, a SPARTAN's reaction time is charted at twenty milliseconds; with the Mark V, and a AI installed, the time translating thought into motion is rendered almost instantaneous."

It goes on to say "[Master Chief] was the first Spartan to test the MJOLNIR Mark V with a Smart AI implemented within the armor during a "live-fire" combat scenario."

The novel Halo: The Fall of Reach places this "live-fire" combat scenario during 2552 before the events of Halo: Reach.

This suggests that not only does Noble team have the ability to carry warship AI, but that doing so has been tested successfully on the same planet they are operating on and(!) is proven to greatly improve the reaction speed and awareness of the recipient of the AI.

Integrating the AI with the MJOLNIR armor would greatly increase the chances of the Spartan making it to the delivery location in one piece while the AI would be safely stored inside heavy armor protected by an energy shield.

  • I would guess it has to do with a lack of technology available. On the ship they will have these small cards that are capable of carrying an AI, but maybe only the canister was available in the lab. But I have never read any of the books and don't know anything about the different generations of Spartans.
    – Sydenam
    Sep 8, 2011 at 10:42
  • 1
    I've updated my question with more of my research. An interesting thing I've recently thought of though: I found evidence that the SPARTAN-IIs were equipped with an upgraded neural interface before they could use the MJOLNIR armor. I couldn't find anything saying that the SPARTAN-IIIs had undergone this upgrade, which if they hadn't shouldn't have allowed them to use the armor, but would explain why they couldn't carry an AI in the same way the Master Chief did.
    – Kalamane
    Sep 28, 2011 at 4:08
  • HALO... so many plot holes...
    – DForck42
    Oct 5, 2011 at 19:34

4 Answers 4


Transcript from the level 'The Package': (bold emphasis mine)

Dr. Halsey (COM): "Before you is an alien artifact neither human or Covenant in origin. Advanced beyond our comprehension... until now. Thanks to Noble Two, the decryption of its data is nearly complete."


The door opens and Noble Team steps in. They begin running into the corridor and reach the end of it: Dr. Halsey's lab. A large sphere-shaped Forerunner artifact hovers outside the lab.

Jun-A266: "What is this stuff?"

Dr. Halsey, still in the middle of preparing the package, moves to another monitor.

Dr. Halsey: "Knowledge. A birthright from an ancient civilization. This AI is its custodian, and she has chosen you as her carriers.


Dr. Halsey: Mankind is outmatched. When Reach falls - and it will fall - our annihilation is all but certain. Unless... we can glean from this artifact a defense against the Covenant. A game-changer. On the level of the conical bullet in nineteenth century, or faster-than-light travel in the twenty-third."

In short, the canister doesn't just hold Cortana. It holds the decrypted data from a Forerunner artifact. Based on this scene, it sounds like not even Halsey knows what data she just pulled; she just downloaded all of it in the hopes that something would prove useful.

It's likely that after finding the information she needed (for example, the coordinates to the first Halo ring), Cortana left the rest of the data behind, and therefore was able to fit into a smaller storage medium.


Third generation Spartans were not more sophisticated then second generation ones. Third generation Spartans were mostly war orphans and post-adolescent, unlike generation 2 Spartans which were modified around the age of 8. As such, the amount of modification that could be done to the Spartan-III's was much more limited. Spartan-III's were also meant to be quasi-disposable and were produced in much larger numbers. It is likely that their armor had fewer features and didn't have the processing power required for Cortana to operate within the suits' computer system.

In Halo 1-3 she is typically protected by Master Chief's armor. If she couldn't efficiently run in Spartan-III armor, she may have required an armored computer core (canister) to be easily transported and protected without losing her operational capacity.

This is mostly inferred from the Halo wiki on SPARTAN-III and my memory of Halo Legends' short story movie collection.


I believe I've discovered the reason for the AI being carried in a Canister in Reach instead of in-armor. The reason is that the characters of Noble Team (including the official, non-customized, version of Noble Six) wear non-standard armor.

At first I thought it was because the Spartan-IIIs didn't have the same Neural Interface upgrade that the Spartan-IIs did, but the quote in the original question shows that this type of interface is essential for equipping the armor at all. Then on the Halo Wiki I found:

"The MJOLNIR Helmet is one of the most crucial aspects to the MJOLNIR system. It is made of Titanium and contains key features like a Heads Up Display that links to the brain and hands, and can identify equipment and display information about it when it is picked up by the wearer. Another feature is the direct neural interface system which connects to a SPARTAN-IIs neural implants. Two core processor chips are implanted into the subjects skull in the rear of the head. This is essentially comparable to an on board computer using parts of the human brain for processing, when the connector at the rear of the subjects head and receptors in the brain link to the helmets on board sensors it creates the neural link needed to move the MJOLNIR suit. The helmet also contains other equipment to protect and aid the user in hostile conditions. This includes: filters to remove toxins from the atmosphere, a supply to provide air to the wearer during EVA, thermal and motion sensors, communications, solar-powered lighting, and imaging and video gear. The helmet also contains the A.I housing, where a ship-borne AI chip is inserted, located on the back of the helmet."

According to this page, all of Noble Team have various non-standard helmets, and Noble Six is equipped with a Mark V [B] variant. Master Chief has a standard Mark V helmet, which is confirmed to have an AI slot.


I believe, I can't remember exactly where I read it, but I definitely remember reading somewhere that Master Chief was carrying a subset of Cortana's AI with him.

In fact, I think in Halo Fall of Reach, Master Chief performs his field tests with Cortana herself. From what I recall, the Dr. kept the majority of Cortana behind to analyze the artifacts that pointed her to the location of Halo.

Or it might be the other way around...the canister contained a subset of Cortana's consciousness that was kept to analyze the artifacts. The delivery wasn't of Cortana herself, but what she had learned since her installation on the Pillar of Autumn to be reintegrated with her greater consciousness.

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