voidstar wrote: ↑Tue Dec 24, 2024 12:31 amIt's been awhile since I've played with those 4-pin connectors on the CD-ROM. Were they left/right audio only, or was it actual signal commands also?
Just left/right line level audio and two ground pins. The drives came supplied with a lead to connect this output to an analogue input on a sound card, usually labeled "CD Audio." Some drives also had a separate two-pin connector for digital audio out, which could be connected to any coaxial S/PDIF DAC or amplifier input.
Later drives had the ability to extract digital audio and send it across the ATA bus, hence why applications like Windows Media Player on Windows 95 had a "digital CD audio" (or something to that effect) checkbox.
voidstar wrote: ↑Tue Dec 24, 2024 12:31 amIn otherwords, is the command to issue the "Play CD" command through that 4-pin connector or does it go through the PATA (IDE) connector?
You have to send an ATAPI command across the bus to control the drive.
voidstar wrote: ↑Tue Dec 24, 2024 12:31 amRight, the host CPU isn't involved, it's just cueing the drive itself.
This, incidentally, is how music (and even some sound effects) worked on many early PC and PlayStation 1 games; the game simply told the drive to play back the relevant audio track at the correct time. Tracks 2 onwards on such game CDs can be played in a regular audio CD player, track 1 being the actual game data in ISO format.
Later on, when CPUs became sufficiently powerful to handle compressed audio, in-game music started being shipped in the form of files on the data portion of the disc.