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Jade Computer Products -   Double D FDC Board
This board was a popular and well designed Jade board.  The manual was perhaps the best at the time in describing the workings of a FDC board.

Double D FDC

I line with unusual names for their other boards Jade call this board the "Double D".
The Double D was an intelligent S-100 based floppy disk controller. It was capable of handling up to four full size (8") or mini (5") disk drives. Provisions had been made for double sided drives. Single and double sided drives could be mixed. The controller was capable of single density or double density disks.
The board contained its own on-board Z80A microprocessor with 2K of static memory. The on-board processor runs simultaneously with and transparent to the S-100 bus. All critical timing was handled on board; data transfers were fully buffered by sector in the on-board memory, two levels of interrupt were implemented on the Z80A, and a wait state generator was used to synchronize the on-board processor to the disk transfer rate. The host system (8080, 8085, Z80, or anything else) need only transfer commands and data through a block of static memory, which could be accessed from the bus. This architecture provided a high degree of timing independence from the host system. Also, since the disk controller program was contained on-board in RAM, the board's operational characteristics were redfinable at any time during system operation.

A WD1791-01 Formatter/Controller was used to encode and decode all data transfers to and from the disk drives. It also provided for the generation and checking of address marks, data marks, and the cyclic redundancy characters. Write pre-compensation could be selected under software control at three levels of intensity, providing flexible data recording. Data separation was achieved by the use of a phase-locked loop to insure maximum immunity to disk speed variation and to enhance data recovery margins in both single and double density.

The manual (one of the best FDC manuals I have seen), for this board can be obtained here
The support software manual with BIOS etc can be found here
To read about the WD 1791 chip, click here.


Other Jade S-100 Boards
Bus Probe    8K Static RAM   Z80 CPU   64K RAM   FDC   1P2S   PSIO


This page was last modified on 10/25/2013