Two years ago I got my family's first desktop computer running again. It was a 386 with a cyrix 486dlc cpu. The bios was an early version of the phoenix bios without HDD auto detect features. The original HDDs we had in the system spin up and I did try keying in the CHS data from the two original HDDs into the bios, but never got anywhere with getting the system to boot from or read from these 30-35 year old HDDs, and I ultimately set up a fresh system from scratch on a compact flash drive.
Thread here: Standard Computer Corporation 386/486, attempt to refurbish

Over this time, I've kept the old HDDs from this machine in case I could find a way to read any data that might be on them another way. Things haven't worked out well on that front.
-The original 386 would give a fixed disk error if I tried to boot with these HDDs, and I wouldn't be able to read them at the dos prompt
-I tried them out with a USB-IDE adapter on a modern PC in Windows 10, but they could not be mounted. Similarly, I tried DMDE, software for modern PCs that can help read and retrieve some data on damaged HDDs, and while that software was useful for other drives I had, it didn't come up with anything for these two ancient HDDs (I later read that modern USB-IDE adapters may not support CHS HDDs of this era, so this experiment might have been meaningless)

I recently got a new 486 machine from 1993, unlike the 386, the bios in this 486 can autodetect CHS settings for drives and it will autodetect these drives. I still can't boot from them, the POST on the 486 tells me there is a HDD controller failure. If I boot from a dos bootdisk or another working HDD in a master/slave setup, I cannot access the old drive, and I cannot run scandisk on the drive. This all sounds pretty bleak, right?

BUT I got to thinking... One of these drives is 1GB in size. That is way bigger than any of the presets in the 386 machine's bios, and given the age of that machine, we probably would have needed to run a drive overlay program like EZ BIOS on the drive when using it with that machine, as given its age and era, its a certainty that it would have been subject to the 528MB HDD limit. Maybe there is something the matter with that initial partition for the drive overlay.

I know the setup program for EZ Bios has some options for repairing this partition, so I ran the EZ BIOS setup on my new 486 with the 1GB HDD connected and autodetected in the PC bios. Unfortunately, EZ Bios indicated that EZ Bios was not installed on this disk so the repair options were inapplicable, however, the setup program has a handy feature where when you ask it to format an HDD and install EZ Bios on it, it asks if you are sure you want to do that, and it displays maybe 5 or so example folders or files from the HDD if there are any, to remind you that you might be overwriting something... When I enter this part of the EZ Bios setup... LOW AND BEHOLD IT SHOWS ME DIRECTORIES FROM THE OLD HDD THAT I RECOGNIZE FROM 30 YEARS AGO, as well as appropriate date modified dates from 1996, which was about when we last used the 386 and this HDD. (Don't worry, I didn't format the drive and I backed out of that option, I went into it just to see if the pre-format warning would display any files/folders and to my surprise, it did.)

So there might still be something there on this HDD after all, even if I can't boot with it... or access it from a bootdisk... or when booting from another HDD with this one set to be a slave...

In light of the fact that I had this glimmer of hope from the EZ Bios warning screen displaying a couple folder names from the drive, I Just wanted to check if anyone had some ideas for other data recovery programs or techniques to try with my 486 to read or access any data that might still exist on the drive. If I were able to get some of my family's original data from the first half of the 90s off of it, it would be very meaningful. Among other things, I was making rudimentary dos games and artwork on the 386 with this HDD 30 years ago and I'd love to recover this stuff if it somehow still exists.