I am assuming that this is an IDE disk.
The most likely cause is that the disk is not recognized by the CMOS.
Run setup and confirm that the disk is visible, and in native mode.
Means that you want to include the ad320 device driver as a boot time loadable drive, and that the root file system of the installation will be on the first channel of the first controller with a...
I think that there was a BTLD diskette for the (ide) CD-ROM driver, and then a bootstring to say which device (primary/secondary, master slave).
Srom=wd(0,0,0) primary master
Srom=wd(0,1,0) primary...