CD-ROM

CD-ROM (an acronym for Compact Disc Read-Only Memory) is an optical media format that was popular in the 1990s. It was superseded by DVD-ROM drives and the Apple SuperDrive in Macs.

Specifications
The Red Book standard for compact discs specified a bit rate of 153,600 bytes (150 KB) per second, referred to as "1x" CD-ROM speed. Audio was encoded in 16-bit resolution at 44.1 kHz. The original standard specified that each disc could contain up to 99 tracks and store 650 MB (74 minutes). The standard was later amended to allow variances of up to 700 MB (79.8 minutes), though some drives have allowed for usable capacities as high as 750 MB (85 minutes).

History
Early Apple CD-ROM mechanisms used SCSI connectors, typically set to ID #3.

External models

 * AppleCD SC (1x speed, model M2850) — required a CD caddy. Introduced in 1988, the internal fan was found to be drawing dust into the CD mechanism which had no external door; it was deemed unnecessary and left out of units manufactured from early 1990.
 * AppleCD SC Plus (1x speed, model M3021) — required a CD caddy. Introduced in 1991, the new drive mechanism added a drive door to keep out dust and could read CDs with more data than the original Red Book standard, up to 750 MB.
 * AppleCD 150 (1x speed, model M3022) — smaller enclosure, still required a CD caddy.
 * AppleCD 300 (2x speed, model M3023) — same enclosure as AppleCD 150, still required a CD caddy. Introduced in 1992.
 * AppleCD 300 Plus (2x speed) — same enclosure as AppleCD 150, but introduced a built-in CD tray and no caddy needed.
 * AppleCD 300e Plus (2x speed, M2918) — included a CD tray, revised enclosure.
 * AppleCD 600e (4x speed, model M3958) — included a CD tray, same enclosure as AppleCD 300e Plus.
 * Apple PowerCD (4x speed) — based on Philips CDF-100. Included Photo CD support with built-in audio/video out.

Internal models

 * Apple CR-503-C (2x speed CD-ROM), used in AppleCD 300 Plus.
 * Apple CR-504-C/K (4x speed CD-ROM, a.k.a. AppleCD 600i)
 * Apple CR-504-L (4x speed CD-ROM), also used in Bandai's Pippin consoles.
 * Apple CR-506-C (8x speed CD-ROM, a.k.a. AppleCD 1200i)
 * Apple CR-507-C (12x speed CD-ROM, a.k.a. AppleCD 1800i)
 * Apple CR-508-C (24x speed CD-ROM)

Driver software
Classic Mac OS included an Apple CD-ROM extension, which at first only supported Apple-branded hardware. This forced users of drives from other manufactures to resort to using a range of 3rd-party drivers with varying degrees of compatibility. Apple started making its CD-ROM extension "universal" with version 5.3.1, which was included with Mac OS 7.6.

The Apple CD-ROM extension was superseded by the Apple CD/DVD Driver included with Mac OS 8.1, which again limited compatibility to drives supplied by Apple. However, this could be hacked to support 3rd-party drives.