garyh@iddic.UUCP (Gary Hanson) (04/15/85)
>>><<<
<credit where due: much of this information came from Midnite Gazette issues
20 and 22.>
If you suspect that your drive is going out of alignment, or if you have
disks that don't seem to get along with your drive, try this simple test.
First, type in direct mode:
OPEN 1,8,15,"M-W"+CHR$(106)+CHR$(0)+CHR$(1)+CHR$(193):CLOSE1
Then, put in a disk that was written on a properly aligned drive (like a
commercial program), and list the directory, load a program, or do most any
type of disk read. A flashing error light will indicate that your drive is
not within a half track of proper alignment. As a further check, type in
the following short program:
1 OPEN 1,8,15:OPEN 2,8,2,"#"
2 INPUT "TRACK";T
3 PRINT#1,"U1:2,0"T",0"
4 INPUT#1,A,B$,C,D:PRINT A;B$;C;D
5 CLOSE2:CLOSE1
When you run this program, enter a track number from 1 to 35. The drive
will attempt to read sector 0 of the selected track. Be sure to try tracks 1
and 35, particularly on suspected bad disks, and any other tracks that strike
your fancy. This will not check the whole track, but will give an indication
of whether it can find the track at all.
The initial M-W command changes a location in DOS RAM that: 1) turns off
'bumps' after errors, 2) turns off checking adjacent half-tracks in case of
bad data, and 3) sets the retry counter so that the drive will only try to
read a selected sector once. This will cause the drive to indicate an error
if the disk and the drive are not aligned to within 1/2 track of each other.
The M-W will stay in effect until the drive is reset (either power-cycled or
reset with a UJ or U; command.)
I've never seen this test fail (my drive is properly aligned), but it
should be effective as a simple check of drive alignment. Good luck.
Gary Hanson Tektronix IDG ...!tektronix!iddic!garyh
Dear Lisa, Mac, and Jack: Sorry, no mice allowed in my house; that's why I
have a cat.