Data Crystal Chips are a form of file storage device used by the UNSC. These data crystal chips are used for transferring "hard" data, meaning data that cannot be transferred over Slipspace or through a transmission because of the data's sensitive or complex nature. Examples of such data include AI data, navigation data, weapon technological charts, etc.
The Data Crystal Chip can be utilized for many things. Here are a few of its uses:
- Carrying the Riemann Matrix for an Artificial Intelligence Construct, like Cortana or Deja.
- Carrying star charts, maps, and other navigational data. These chips must be destroyed if contact is ever made with the Covenant, as per the Cole Protocol. This did not happen aboard the UNSC Circumference during the Battle of Reach, so Blue Team was sent to destroy its Data Crystal Chip.
- Carrying sensitive data, such as intelligence; Dr. Catherine Halsey had compiled two of these with all known information on the Flood. One data chip had a complete set of information on it, including how Boren's Syndrome affects the Flood's ability to assimilate an individual into the Flood super-organism. The other data chip had this data omitted, since if the complete report were to be found then Sergeant Major Avery J. Johnson could be killed and dissected by ONI, because of his being afflicted with the disease.
The Data Crystal Chip was seen extensively throughout Halo: Combat Evolved, as John-117 uses a data port on the back of his helmet to ferry Cortana between his armor and other computer systems. However, it is not seen or mentioned at any point during Halo 2. John-117 is instead seen directly downloading Cortana via physical contact with his new armor.
In Halo 3, the Data Crystal Chip is seen once again. However, unlike the transfer in Halo: Combat Evolved, which required physical contact with a system, an AI can now "jump" from chip to system and back, in addition to the physical transfer. This can most noticeably be seen on Halo, the final level of the Halo 3 campaign. A possible reason for this is that the Data Crystal Chip was upgraded along with John-117's new MJOLNIR Powered Assault Armor.
- A Crystal Chip is seen on some of the Cafeteria tables on the Halo: Combat Evolved level Pillar of Autumn.
- In Halo 3, the color of the Crystal has changed to a blueish-purple hue as opposed to the aqua color of the Halo: Combat Evolved Crystal.
- The Data Crystal Chip did not make an appearance in Halo 2. Instead, Cortana could transfer from the more advanced MJOLNIR Mark VI armor straight to any electronic system in direct contact with the suit. However, despite the armor in Halo 2 being the same suit as in Halo 3, the Data Crystal Chip makes a re-appearance, and the direct-transfer system no longer seems to exist. It is possible that this was a deliberate choice to more resemble the transfer system seen in Halo: Combat Evolved, although it is also possible that it was merely for dramatic effect; in the opening cutscene, Johnson, thinking John dead, is able to yank the chip out of the suit, and then ask John about her whereabouts when he realizes the chip is empty. There is one other possibility that the armor took too much damage and was unable to transfer electronically.
- Despite this Cortana is able to exit and enter the chip without it connecting to a computer hinting that the chip may have been upgraded in the same way as the suit.