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.
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.
