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psystem.txt
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1985-09-29
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57 lines
READ PROBLEMS ON HALF HEIGHT DRIVES
WHILE USING P SYSTEM PASCAL
If you have had troubles with programs written on the UCSD p system
working on half height drives, such as TEAC 55B drives which are
commonly added to the IBM PC, you may be able to modify your drives
to solve the problem.
We had problems transferring files with Advanced DB Master, which
is written in P system pascal. It is logical to assume that other
programs written on the P System, would exhibit similar symptoms.
We would pick up a lot of read errors, and sometimes the computer
would simply not recognize that there was a disk in the system. At
first look, it appeared that the problem was the disk drive, but we
even replaced the drive with a brand new one, with no luck.
One of the first things that the P system does when it accesses a
drive is to read the volume name that is located on each formatted
P system disk. If it does not read this volume name, the system
will assume that there is no drive in the computer, and simply will
not access any files connected with that drive.
Many half height drives are built with a solenoid that drops the
head onto the disk when the computer needs to access the drive.
Most full height drives leave the head resting on the disk whenever
the door is closed.
The operating system sometimes will not allow enough time for the
head to drop onto the disk and read the volume label. Therefore,
it can erroneously lock that disk drive out of the system.
The solution on the TEAC drive is to adjust an allen screw that
controls the height of the head while the solenoid is in the open
position. Turning this screw about two turns counter clockwise
will allow the head to ride on the drive at all times. This
cleared up our read problems with Advanced DB Master entirely. I
can see no reason that this would be any more damaging to a disk
than the regular full height disk drives are.
Most other types of half height drives would probably have a
similar adjustment that could be made to bypass the head load
solenoid.
Perhaps one of you programmer types out there would be able to come
up with a software patch to the operating system, to allow a little
more time before it reads the volume label. If so, please write or
call me and let me know.
Frank Sousa
MTSI
Building 102 Spokane Industrial Park
Spokane, Washington 99216
(509) 926 6705