This was Konan's answer for ST-506 5" hard disk drives.
The Konan DGC was an intelligent 5-1/4" Winchester disk controller for the
S-100 Bus which meet the 1EEE-696 specifications. The DGC could control up
to two disk drives, with up to eight heads and 4096 tracks. The command set
for the DGC provided all of the required functions to interface the host
computer to a standard 5 1/4" Winchester disk with minimum host software
overhead. Typical drives were the Seagate ST-506, Rotating Memories
RMS-512 and Computer Memories CMS-5616. The board had an on-board Z80A
that handled all the disk interface functions. The board utilized 8
I/O ports on the bus (only 5 were utilized). Sector sizes were either
256 or 512 bytes.
The manual for this board can be obtained
here.