Analog audio out

It's pretty much a vestigial thing anymore. It used to be necessary in order to play sound from a CD, but since... Windows 95, I think, or maybe it was Win98... there's been the option of running the digital signal over the IDE bus, making the cable pretty much pointless.

Wouldn't attaching this cable help in lowering data having to move through the IDE channel, thus helping improve system performance a bit?

Not really. The only time it'd ever be used is when you're playing music directly off a CD, and that's a pretty small amount of data to move across the IDE bus anyway.

I mean, if you wanna play a CD in a drive running in PIO mode off an ISA controller in a 486 while playing games and downloading porn in the background, then yeah, connecting the cable might help performance a couple percent, but otherwise, you'll never see a difference.

Don't quote me on this but I think Windows 95 only lets one application play audio at a time. (No kMixer driver) So you need to use the CD audio cable in order for the computer to be able to play other sound at the same time it's playing a CD audio track.

Windows 98 SE, I think, comes with the kernel mixer meaning it no longer needs the CD audio cable, multiple apps can play audio simultaneously and the sound card doesn't have to have its own analog audio mixer built in (thereby saving a few pennies of cost to manufacturer)

Here's another way to think of it: it's the same thing as those headphone jacks that CDROM drives had back in the ancient times. You just get to connect it internally instead of around to the line-in on your sound card.

Did anyone ever use their CDROM drive as a CD deck? All of the manufacturers seemed to think that users wanted that feature. They even had the various playback CD player playback controls for awhile.

Remember, not every drive was even able to extract audio digitally! And if it it could, it might be full of audible errors. And the drive might be placed in a faster reading state than 1x, which would generate more noise.

The CD audio cable was designed for CD-audio tracks being played back directly from the disc. CD audio is an uncompressed audio signal without error correction, making it ideal for the CD drive to playback without any assistance from a sound card. This was very important in DOS, where the systems of the time could not afford the CPU power to send a large amount of digital audio through the sound card. Your average sound card was not particularly efficient at processing multiple streams of 16-bit stereo digital audio data at the same time.

SATA DVD drives do not even have CD-audio cable headers. Everything that is played on those drives comes out 100% digital until it gets to the audio output of your sound card. It is only necessary if you have a version of Windows that does not allow the digital processing of CD audio through an IDE cable or are using DOS.

Yup it's easy to forget how demanding 16-bit, 44.1 kHz was back then.