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.
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.
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
01/08/2011