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Heath/Zenith  Z-217  Winchester Disk Controller
This was one of the two S-100 boards Heathkit supplied with their Z/H-100 computer system.

Z-100 HDC

This was a sophisticated S-100 board at the time. It had a number of custom PAL's.  In order to access the Winchester disk however you had to connect the S-100 controller board to a "data separator" board which was then connected to the hard disk itself.  This is shown in the picture below.

The Data Separator Board
The Winchester data separator uses a conventional phase locked loop. This board also contained the ECC logic and the write logic. Maximum record length (including ECC bytes) was 526 bytes if the following parameters are to be maintained :
Maximum   correction   span   =   8   bits
Single   burst   detection   span =  32   bits
Double   burst   detection   span =  2  bits
Non-detection   probability  =   2.3   x   10E-10
Miscorrection   probability   =   1.25   x   10E-4

The S-100 Main Processor Board
The main processor uses a 2900 bit slice processor as its CPU. The data path was eight bits wide while the microsequencer word length was forty-eight bits wide. The system, as implemented, had the ability to perform all logical operations (AND, OR, XOR, INV) as well as mathematical operation such as add, subtract, multiply and divide. The processor interpreted all commands received from the host, executed them, and then returned status to the host. The processor also performed all motion control commands for the disk drives as well as calculating the error correcting code (ECC) and actually performing error correction.
The schematic for the S-100 board itself is shown here.  The Z-217 Technical (hardware) manual can be obtained here.

Data Seperator +Drive

Heathkit supplied a large body of software to bring up a new hard disk. Such as initializing and formatting the disk, as well as software to test the system. See the ZDOS Winchester Supplement manual here as a great example of how well the documentation was done.


Other Heathkit S-100 Boards
Motherboard    FDC      Winchester Disk Controller   256K RAM    ARCNET


This page was last modified on 10/25/2013