S100 Computers

Home S-100 Boards History New Boards Software Boards For Sale
Forum Other Web Sites News Index    
 
Vector Graphic Micropolis Floppy Disk Controller
Very early on in the S-100 era, Vector Graphic made a decision to go with hard sectored floppy disks. They joined up with a company called Micropolis who were one of the first to make floppy disk drives available to the S-100 community.  The only other significant hard sectored disk system at that time was the popular Northstar disk controller system.  However over time the soft sectored disks (1 index hole per disk instead of 16) won out. Thanks mainly to the reliability and flexibility of the Western Digital controller chips. and the common adaption of CP/M to the format. In the end even Vector switched over (see here).
Vector took the Micropolis S-100 board and relabeled it with their logo. Here is a Micropolis 5 1/4" FDC board.

VG-M FDC

The controller contains the following major functional units:
Control logic to interpret CPU selection and respond to CPU commands.
A sector separator that separates sector and index pulses and keeps track of each sector as  it passes under the  read/write head. Write logic that converts parallel-form bytes from the CPU to serial data suitable for recording on the disk.
Read logic that converts the serial data from the disk to parallel-form bytes for transfer to the CPU.
Bootstrap PROMs for reading sector zero of the system disk into RAM, then starting  the program in RAM.

Disk Data Format
Data is recorded on the disk in concentric tracks. The outermost track is track zero. Each track is divided into 16 sectors. The beginning of each sector is indicated by a sector hole punched in the disk. An index hole is located halfway between the holes for sector 15 and sector zero. The sector and the index hole are sensed by a photo transistor in the disk drive. Each disk sector consists of a preamble, sync byte, header, data, a checksum,  and a post amble.  Details are described in the manual. 

The normal controller base address was C000H-FC00H but the board could be jumpered to any 1K boundary. This was a large bite the 64K available address space.

You can find out more about this board  from the manual here.

 

Other Vector Graphic  S-100 Boards
Dual FD-HD Controller    FlashWriter-II    Bitstreamer-II   48K-RAM    64K-RAM   8080-Board  
8K-RAM   EPROM  FDC   Micropolis-FDC    Z80-Board    SBC 

 

This page was last modified on 07/28/2014