New details of the custom chips designed by Apple for its forthcoming virtual reality and augmented reality headset indicate it will need to be wirelessly tethered to a phone or a similar device for the most advanced features, just as early versions of the Apple Watch required users to carry their iPhone with them.

Apple completed work last year on the chips, including the key system on a chip (SoC),  which has many different components of a device etched on a single piece of silicon, said two people familiar with the situation. The SoC and two other Apple-designed chips for the headset hit a milestone known in the semiconductor industry as tape-out, which means the physical designs of the chips are complete and ready for trial production. It’s a key stage in development of the headset, which The Information previously reported was expected to debut by next year at the earliest, though Apple could push the release back even further.