Great to hear that you can access the BIOS on your MDR - that makes restoring the settings to what they need to be WAY easier.
(As you already know, for that purpose, any video card that fits a slot in the MDR should work… and as you know, you just have to cut a hole in the back of the MDR, where the AT-Keyboard connector is hidden).
Don’t use “restore optimal system settings” (or whatever it is called in this BIOS). That’s not the right settings for the HDR/MDR, and certainly not “optimal” haha.
A list of the needed BIOS settings for the HDR/MDR can be found here:
https://www.sonido-7.com/d8b/files/hdr_and_d8B_new_mb_bios.pdf“LBA” stands for “Logical Block addressing” and some hard drives need that, to work correctly in the HDR/MDR/D8B. So, you might want to try flipping that one to try what happens.
Also, while drives can be auto-detected on startup, there’s also an option in the BIOS where you can auto-detect the installed drives, and then modify settings as needed - like, for LBA mode, for example. So, you’d go in the BIOS and do the Harddrive detection thing (not in front of it right now, but it’s one of the last choices on the main screen before the save and exit option). It should detect “something” and then you can make the needed changes. When then going back to the first BIOS screen, it will no longer say “AUTO” for HD detection, but “User” and if saving the changes in the BIOS, the MDR will try to boot with the new settings, next time.
As for the Harddrive jumpers… which drive are you trying to replace? The system drive or drives inside the drive caddy?
The system drive should always be jumped for “Master” - no exceptions.
The drive in the caddy, is normally connected to the second (of two) IDE controller in the HDR/MDR (each controller can have one “Master” device and one “Slave” device connected. Cable Select is an attempt to have the computer figure out what’s what automatically… but that doesn’t often work out).
Typically, you’d want to have the drive in the caddy jumpered to “Master” as well… but since there’s not usually any other device connected to the 2nd IDE controller, if it’s set to “Slave” it would likely still work, at least from the computer hardware perspective - but I’m not sure if the MDR/HDR Operating System expects these to be found in the “Master” position, though.
Anyway… from my understanding, any drive you use in the HDR/MDR should usually be jumpered to “Master” (but I didn’t carefully read Mike River’s book… not sure if he makes a different recommendation, there).
So, between making sure the BIOS settings are right, the jumpers on the drives are set to Master, and trying if they’re recognized in the BIOS by trying to detect them from there and trying “LBA” if the Operating System still doesn’t find them, should hopefully help to get these drives recognized.
Best of luck!