IBM/Xebec HDD Controller with Seagate ST-412 - Park Via DEBUG


WARNING:   The following procedure is only for the ST-412.
By "IBM/Xebec HDD Controller", I mean the one supplied by IBM in their IBM 5160s.
The following procedure has not been tested on other controllers.


Seagate's specs for the ST-412 indicate a landing zone (cylinder) of 319.

It turns out that the ST-412 doesn't accept a command to move/seek to cylinder 319.  A quick check revealed that the largest cylinder accepted is 305.  I acknowledge that it could be the IBM/Xebec controller causing this.

The following DEBUG based procedure simply moves the ST-412's heads to cylinder 305.


1.  Either boot from a DOS boot disk that contains DEBUG.COM, or boot from a hard drive where the C:\DOS directory contains DEBUG.COM

2.  Examine the ST-412's stepper flag. It will probably (repeat: probably) be close to the cylinder 0 position, as pictured below.
    The actual position will depend on what files were accessed at boot time, and where those files are physically on the ST-412's platters.

st412_cyl_0.jpg


3.  Run DEBUG.COM

4.  DEBUG will present a dash ("-") prompt. When you see that prompt, enter the following commands (shown in brown):

         - a 100
         xxxx:0100 mov ah,c
         xxxx:0102 mov cx,3141        <----- Per here, 3141 hex = sector 1 on cylinder 305
         xxxx:0105 mov dx,80
         xxxx:0108 int 13
         xxxx:010A jmp 10a
         xxxx:010C                 <----- at this line just press the [ENTER] key - this will return DEBUG's dash prompt
         - g=100

After the "G=100" line is entered, it will appear that the machine has locked up.  We expect that (because of the "jmp 10a" above).


5.  Examine the ST-412's stepper flag.  It should be in a position that is close to that pictured below.

st412_cyl_319.jpg


6.  Power off the computer.