I have used ATAPI DVD drives even on 486 machines and they work fine.
I wonder if this DVD drive has a short circuit on the IDE connector somehow.
Have you tried it on another machine?

Unfortunately this is the only system with IDE that I have running right now, and I don't have an adapter to give it a shot in a more modern one. Do you think a short on the DVD's side could cause BIOS to flip out to such a degree?

Are the 2 HDDs on one channel and the DVD drive on the other?

I still think its a jumper combination problem. I had this kind of problem several times in the past 25 years with ide computer.

If the DVD drive is hooked up by itself does it work?

Are you using a 40 or an 80 conductor cable? The 80 conductor cables are more rigid and the wires are much thinner. With it being a newer drive, it might not like the older cables.

Assuming that what you say is true.
If you change BIOS to Auto Detect before you do anything.
If you put Master jumper on back of DVD drive, or cable select work sometime.
Then you connect DVD drive on the 2ndary IDE channel making sure the red line on the cable is matches pin 1 on both drive and motherboard.
And assuming u do not have a bad cable than your drive is either bad, or its incompatible.
It's not rocket science on your age of hardware.

BTW both your HDDS should be on IDE 1 DVD on IDE 2 alone

Use a different DVD drive. Samsung did something to their later IDE drives that causes detection problems on some older motherboards. I have a 2005 drive from them that causes exactly the same behaviour as you describe on one motherboard, but works fine on another (later one).

This happened to me once when I had the IDE cable plugged in upside-down. I thought the IDE controller was broken, but it was just that I was using an IDE cable without the orientation tab and didn't check.

I had a similar issue once, turned out to be some weird jumper setting on the hard disk.

Apparently, that particular hard disk had two settings for "Master". One was "Master without Slave" and the other was "Master with Slave". If the wrong setting was selected, neither the master nor the slave drive were recognized by the BIOS.

kalohimal wrote on 2020-09-05, 05:18:

Are the 2 HDDs on one channel and the DVD drive on the other?

Thinking it might be sensitive to channel order, or playing nice with a specific HDD I've tried having it slaved to both hard drives, as well as master on its own IDE channel. No go in every case unfortunately.

renejr902 wrote on 2020-09-05, 05:35:

I still think its a jumper combination problem. I had this kind of problem several times in the past 25 years with ide computer.

I thought so as well, but I tried it various in master, slave, and CS mode in various positions on the cable, and both controllers, to no avail.

cyclone3d wrote on 2020-09-05, 05:45:

If the DVD drive is hooked up by itself does it work?

Are you using a 40 or an 80 conductor cable? The 80 conductor cables are more rigid and the wires are much thinner. With it being a newer drive, it might not like the older cables.

If it is hooked up by itself it does not work, no. Oddly if the IDE cable is connected it won't behave as if it is powered on, i.e. pressing the eject button does nothing. However, if it is only connected via molex, with no data cable, it behaves normally - will open when the button is pressed. Another oddity.

I only have 40 pin cables, unfortunately, so can't test it's behavior with an 80 pin cable right now. I should order one, at least to have on hand (this system is ATA-33 but yes, good for testing to have on hand).

yawetaG wrote on 2020-09-05, 05:54:

Use a different DVD drive. Samsung did something to their later IDE drives that causes detection problems on some older motherboards. I have a 2005 drive from them that causes exactly the same behaviour as you describe on one motherboard, but works fine on another (later one).

Yesterday I ordered another drive (different manufacturer) hoping something like this is the case (as opposed to a defective drive). In googling I did come across a couple of folks saying the same thing, and this particular drive was manufactured in 2008 I believe so that seems possible.

Thermalwrong wrote on 2020-09-05, 14:11:

This happened to me once when I had the IDE cable plugged in upside-down. I thought the IDE controller was broken, but it was just that I was using an IDE cable without the orientation tab and didn't check.

Yeah the orientation tab is a lifesaver. 🤣 Fortunately the cables I'm using in this system all have tabbed connectors, or I'd likely have done that a time or three just in the last day.

Joseph_Joestar wrote on 2020-09-05, 14:17:

I had a similar issue once, turned out to be some weird jumper setting on the hard disk.

Apparently, that particular hard disk had two settings for "Master". One was "Master without Slave" and the other was "Master with Slave". If the wrong setting was selected, neither the master nor the slave drive were recognized by the BIOS.

Yeah, I was initially certain it must be a jumper issue - that would have been a fast fix. Both have pretty straightforward M/S/CS jumper settings, so it's still a mystery.

Having checked and rechecked cables and jumpers, and tried every possible cable combination at least twice each, I've put this unit aside and put the original CD drive back in (which works perfectly). I have another DVD drive on the way, so will test it at some point in the near future. Thanks for your efforts to help, much appreciated. 😀