We don’t really do discs anymore. We used to do them for builds on dev machines, but now that we’ve all got sufficiently fast internet connections and sufficiently large hard drives, all we do are digital builds now. Even our submission candidates are digital now. To my understanding, we really only make discs when we’ve passed cert and we’re going to gold master. Even the physical discs you get today often just contain the same internet-based installer that you’d download from the digital store.
I don’t think disc builds have been a thing since two console generations ago, the X360/PS3/Wii era. We actually made regular disc builds back then because we had to test things like streaming data off of the optical disc. I remember having to come up with solutions for desynchronized audio issues because data were still being streamed from the disc when we loaded a saved game from a cold boot at a particular place in the game I was working on. Nowadays we can fully install the game to the SSD and we no longer have to worry about those kind of technical issues.
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