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Cromemco - 64 FDC  
The 64 FDC was  Cromemco's third-generation floppy disk controller board. It  offered substantial feature and benefit improvements over the earlier 4FDC and 16FDC boards.

Cromemco 64FDC

The 64FDC provided a complete system for floppy disk operation: serial I/O for an RS-232 terminal, a read only memory programmed with system bootstrap and diagnostic routines, and full read/write/format capability for any combination of single or double sided, single or double density, 5" (mini) or 8" (maxi) floppy disks. The 64FDC normally handled up to 4 drives in a daisy-chain configuration, although 16 drives may be chained if the drives decode the 4 drive-select  lines completely. The 64FDC had fewer parts than its predecessor, the 16FDC, and was therefore more reliable. Yet it had more features. The 64FDC supported the then new slim line eight-inch drives such as those featured in the Cromemco System 3A. It also included write pre-compensation to ensure that it worked reliably on the inner tracks of a wide variety of eight-inch  drives. All timing on the 64FDC was referenced to an onboard crystal clock. This included the head-stepping rate, the motor-turnoff timer, interval timers, the watchdog timer in the auto wait circuit, and the pre-compensation delay in  the write  circuit. The 64FDC included an 8-channel interrupt system connected to the flag bits of the disk controller. One of the interrupt inputs could  be connected to the crystal clock for use with the real-time multiuser, multitasking Cromemco Cromix Operating System.  Single-density data was recorded in the FM format while double-density data uses the MFM format.   Like the Vector Graphics FDC, Cromemco utilized the 1793 chip rather than the 1791 (inverted data bus) chip. If you need to find out more about these chips see here.
 
The very extensive manual from Cromemco for this board can be obtained here
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Other Cromemco S-100 Boards
ZPU  SBC   4KRAM  16K RAM  64KZ RAM  64KZ-II RAM  256KRAM  8KBytesaver  Bytesaver-II  
16KPROM  32K Bytesaver  4FDC   16FDC  64FDC  WDI  WDI-II   STDC   DPU
4PIO   8PIO   TU-ART  D+7A I/O   Dazzler  PRI   GPIB Board   XMU  XXU  Other Boards

 

This page was last modified on 10/25/2013