@tubetime I have a stalled project to RE the WDXT-GEN BIOS, because I got tired of it's shitty/uninformative error messages.

If you don't use one of the 4 hardcoded drive types, the BIOS will write your drive type (CHS, Write Precomp, Reduced WC, etc) to somewhere on the drive that's _not_ the data area.

It's not actually clear to me where the data is actually written, but IIRC, the "magic" value to provide to the controller is "write to track 0 with an out-of-bounds sector".