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I have a MS-6340 micro ATX motherboard in my retro PC. It has multiple audio connectors and one is called JAUX1. It can be used to input analogue stereo sound.

But the description in the motherboard manual about this connector is strange:

This connector is used for DVD Add on Card with Line In connector.

I have googled and searched eBay for "DVD add on card" but I found nothing. Maybe they have chosen the wrong word and meant "DVD drive"?

Because you can read here CD drives (and also my DVD drive) have an audio out connector. But that's a feature of CDs and not DVDs... Also the mainboard has another connector for this called JCD1.

As you can see I really don't know what a DVD add on card is. Anyone got an idea?

manual screenshot

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    Sure this is on topic? That board is barely 15 years old made for 2 GHz CPUs and well capable of running Windows 10 in everyday operation. Maybe not the newest gear, but not a Retro PC by any angle to look at.
    – Raffzahn
    Mar 19, 2023 at 16:19
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    @Raffzahn: It looks to me like this board, at least in its earliest versions, dates to 2000, and supported K7 Athlon/Duron CPUs in the 600-800 MHz range. Still a little borderline, but at least a little more retro than you're suggesting. Mar 19, 2023 at 16:22
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    We’re moving forward inexorably. Eventually questions about SSDs and ARM chips will be de rigueur for retrocomputing. ;) Mar 19, 2023 at 17:29
  • @NateEldredge The Board was sold up to at least 2007 (latest BIOS Version is of 2007) and CPUs up to Athlon XP with 2.1 GHz (introduced 2002). Quite different from what your selection suggests and for sure still a capable machine. Athlon front side bus was remarkably stable during those years and supporting a wide range of speeds - one reason why I liked the series, as updates could be made several years later.
    – Raffzahn
    Mar 19, 2023 at 19:36
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    @Raffzahn fair enough, there were multiple versions of the board; but even version 5 was released in 2001, which is quite a bit more than 15 years ago! And its layout doesn’t match that shown in the question (which matches the layout used in the first version of the board). In any case, this question is about DVD support boards (MPEG decoders) rather than a specific motherboard; and MPEG decoders have been obsolete for a long enough period to qualify as retrocomputing as far as I’m concerned. Mar 19, 2023 at 21:43

2 Answers 2

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Possibly it means a hardware MPEG-2 decoder card. Those were common in the fairly early days of DVD, when typical desktop CPUs were not fast enough to reliably handle software decoding.

Here is a press release about an early one from 1996. The specs mention both analog and digital audio outputs.

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    This is probably what it's referring to, yes. I have a slightly later Sigma Designs "Hollywood Plus" DVD/MPEG2 hardware decoder card from the Windows 2000/XP era that would line up temporally with when the referenced motherboard was first introduced. It features an audio pass-through to take audio in from the optical drive (CD Audio), mix it with decoded MPEG audio, and send it on to the computer's sound card (or motherboard audio in) for systems without a dedicated input for the decoder card but there would be advantages to having a separate input like adjusting the levels independently, etc.
    – mnem
    Mar 19, 2023 at 23:32
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    It's probably worth pointing out that DVD hardware decoder cards aren't always just strictly for DVD/VCD playback. The one that I have also supports hardware accelerated video playback in 3rd party games / software (for things such as intro movies, in game cut-scenes, etc) so long as it supports Sigma's licensed API.
    – mnem
    Mar 20, 2023 at 16:44
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    There was also a very popular (at least in my area) Creative Labs Encore bundle that bundled a DVD-ROM Drive and MPEG2 card. LGR did a video about it, and it also had that Audio header Mar 20, 2023 at 18:02
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In old days of early DVD drives, CPUs were so slow that even high-end CPUs would struggle to play an MPEG-2 stream from the DVD disc, so an add-in card with an MPEG-2 decoding ASIC was required by most systems.

It was a short lived card, because it was expensive and only required by those who wanted to play DVD videos in their PCs, not to mention that just 1 year later, Pentium II 300MHz was released which was capable of software MPEG-2 decoding.

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    This was largely just bad decoder implementations and/or bad data pipelines with lots of unnecessary memcpys, not a fundamental limitation of the CPUs. A 450 MHz K6 (cheap AMD x86 clone from back then, probably comparable to ~300 MHz Intels) could play DVDs at something like 30-40% cpu load running MPlayer. Mar 20, 2023 at 22:32
  • @R..GitHubSTOPHELPINGICE, video playback is latency-sensitive. "Capable of software decoding" is not the same thing as "capable of software decoding at a constant 29.97 frames per second, regardless of any other tasks the computer may be performing". Windows 9x, in particular, tended to have hitches in playback any time the hard drive was accessed.
    – Mark
    Mar 27, 2023 at 20:50
  • @Mark: This is prerecorded video not realtime video and you can decode and buffer ahead as much as you like. Mar 28, 2023 at 14:23
  • @R..GitHubSTOPHELPINGICE, you can buffer ahead at a cost of about 1.5 MB per frame. A system slow enough that a decoder card is a good idea probably only has enough RAM to buffer maybe three frames.
    – Mark
    Mar 28, 2023 at 21:23

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