CD-ROM

CD-ROM offered several hundred megabytes of storage — hundreds of floppy disks’ worth. This capacity enabled full-motion video, voice acting, CD audio soundtracks, and sprawling game worlds. The technology transformed expectations: games became cinematic experiences. Some developers filled the space wisely; others padded with forgettable FMV. Either way, CD-ROM defined 1990s gaming.

Fast facts

• Capacity: depends on disc length, not on the format. Sega’s Mega-CD specification works to a 60-minute disc: 270,000 sectors of 2,048 bytes, or 539.968 MB. The familiar 650–700 MB figure is the later 74-minute disc.
• Sector: 2,048 bytes of data per sector, one sector per frame, 75 frames a second.
• Read speed: 1x = 150KB/s; improved over time.
• Gaming adoption: started early 1990s.
• Advantages: capacity, CD audio, cheap replication.
• Disadvantages: load times, seek times, scratches.

Gaming impact

How CD-ROM changed games:

• Voice acting: full dialogue possible.
• FMV: full-motion video sequences.
• Music: CD-quality soundtracks.
• Scope: larger worlds, more content.
• Multimedia: encyclopaedias, educational software.

Capacity is a function of running time

A CD-ROM is an audio CD with data in the sectors, so its size is measured in minutes before it is measured in megabytes. Sega’s Mega-CD Disc Format Specifications does the arithmetic openly for a 60-minute disc: 75 frames a second, 60 seconds, 60 minutes — “75 x 60 x 60 = 270,000 fr[ames] (sectors)”, and “270,000 x 2KB = 540MB”. A shorter CD-S format gives 90,000 sectors and about 180 MB.

Sixteen sectors are gone before a developer sees any of it: “Sector numbers #0 to #15 are reserved for the system area”, with the boot sector at #0.

Platform implementations

CD-ROM in gaming:

• Mega-CD: Sega’s add-on (1991).
• PC CD-ROM: standard drive adoption.
• PlayStation: CD as primary format.
• Saturn: also CD-based.
• 3DO, CD-i: multimedia-focused platforms.

See also

• The 7th Guest
• PlayStation
• FMV