WD400JB and new computer

I am a hobbyist. I have created a simple IDE/PATA interface for a new computer. Most disk drives work fine, but WD drives give me problems, and I am trying to find out why. Essentially, I am writing a very primitive BIOS that reads and writes sectors using LBA. I am working at the assembly language level. When I do the IDE disk diagnostic command 0x90, it returns the code 0x01, which is no errors. I then try to read a sector using 0x20. The command completes, but gives me status code 0x51 with error code 0x04, media change. Also, the buffer does not seem to contain disk data. If I try to read a sector again, it hangs – I think because the drive is not setting DRDY. Mechanical disk drives from other manufacturers to not behave this way, nor do CF drives in an IDE adapter, or solid-state IDE drives. I would really like to get these legacy WD drives to work. Perhaps there are some manufacturer-specific initialization commands that I am not aware of. I could not find any detailed technical documents about this, I assume because most of these drives were sold to OEM. But, since they are now obsolete, I was hoping someone could give me enough information to get them working.Thanks.

Hi,

Not sure if any of the user have infomation about this unit.

Hopefully someone does and you get the information that you need. 

Just in case send a pm to  fzabkar he does have a lot of information about internal drives.