One of my completed is a Philips P3105.
NEC V30 8mhz 768kB ram (!), Both 3,5dd and 5,25dd fdd and a Miniscribe 8425X 21MB hdd.

The hard disk is connected too the onboard xta controller. Worked fine until recently.
The number of bad sectors is increasing fast and damaging all kind of files. So I consider it dying.
https://arvutimuuseum.ee/th99/h/txt/2709.txt

Now I do have another XTA disk: a WD93038X (31MB) I know it has just a few bad sectors and the number has been stable for years. I consider it ok.
https://arvutimuuseum.ee/th99/h/txt/4810.txt

The trick is not just to swap them but also to configure the new drive.
The only partition was originally 31MB and is accessible in dos, I can r/w files but it's not configured as 31MB: Fdisk sees a 31MB partition on a 20MB disk.

Using debug g=c800:5 (or ca00, cc00, ce00) will just hang the system. Not usable here.
Philips provided some files that configure the system. Among them is WDHDinit.exe
This should allow me to alter the configured drive parameters. But it will only allow me to change there interleave and lowlevel format the drive.

The software also tells me there is a 615 cyl and 17sect drive present, but defects are registered at cyl 887 888 and 889 (?).
There seems no way to tell the software to use all 27 sect. It's like using a rll drive as mfm now, lossing half the available space.

In my other compete (Phillips P3120) it runs like a 31MB drive just fine.
Would this be a limit by the onboard controller?