Section 2 - Commodore Computers

126 COMPUTEI COMPUTE! May, May. 1Q82.lssue 1982, Issue 24
GeHingYour
Getting Your
Atari Disk Drive
Up To Speed
UpToSpeed
Bob Christiansen
Bob Christiansen
Vice-President Vice-Presicient Quality Software
Reseda, CA
Resedo.CA
[fyou have an Atari 8 10 disk drive that has always
wo rked reliably, then count yourself fortunate. At
Quality Software we have spent about half our
If you have an Atari 810 disk drive that has always
worked reliably, then count yourself fortunate. At
Quality Software we have spent about half our
original investment repairing our Atari drives.
Other publishers of software for the Atari Personal
Computers have told us of similar experiences. It
Computers have told us of similar experiences. It
appears that the 810, at least the original version,
was not built ltlo to work eight hours a day. In Atari's
defense, substantial improvements have been
made to thee 8S10 since it first appeared and the
reliability of newer models should be better.
reliability of newer models should be better.
One of the most frequent problems with the
810 is that it can get out of speed adjustment. The
810 is supposed to spin diskettes at 288 revolutions
8 10 is supposed to spin diskettes at 288 revolutions
per minute (RPM). The hardware, which was
actually designed to operate at 300 RPM, , has a
potentiometer that allows the RPM to be adjusted
potentiometer that allows the RPM to be adjusted
over a considerable range. Speed acUustment adjustment capa­
bilily bility is imponant important because Illany many faClors factors can vary
the actual speed of ol the drive. The speed potentiometer
OIlle le r is not nol accessible without removing reilloving the drive
cover, but anyone who \\Iho can handle a screwdriver
can, with proper care, adjust the speed of their
own 810 drive. We will explain later how to do this.
own 8 10 drive. We will ex pl ain later how to do this.
The Symptoms Of An Improperly Tuned Drive
The symptoms exhibited by a drive that is out of
adjustment are usually that it starts getting format
errors (drive is tOO fast) o r that someone else cannot
errors (drive is too fast) or that someone else cannot
read a diskette that your drive wrote (drive is too
slow). Other reading and writing errorse rs may
also occur, but these two symptoms are the most
also occur, but these Iwo symptoms are the most
common.
C0I11111 o n .
A drive thai spins too fast is in danger of im
A drive that spins too fast is in danger of im ­
proper formatting. It may not write all 18 sectors
before completing oneo revolution. TheT last sector
is written wl·itten on top tOP of the first, destroying g the first. A
fast drive will also have trouble writing a sector
fast drive will also have trouble writing a sector
onto O l1tO a diskette diskclle that was formatted ono n a slower
drive, because it will overwrite the physical space
drive, because il will overwrite the physical space
provided on the diskette.
A drive that spins too slowly packs the data so
close together er that the diskette becomes hard to
read, especially by another drive turning at a faster
speed. Slower drives can usuallyy read diskettes
formatted and written llen at faster speeds, but the
reverse is nOt true. Thus, if yo ur friend cannot
reverse is not true. Thus, if your friend cannot
read a disk that you wrote, the most likely event is
that his drive is normal and your drive is too slow.
that his drive is normal and your drive is too slow.
If your drive is LOa too slow, , youu Illay may never know it
until yo u make a diskette and se nd it to a frie nd.
until you make a diskette and send it to a friend.
The fact that outsidee tracks have a bigger
circumference than inside tracks means that data is
... the 810 ... was not built to
work eight hours a day.
...the 810... was not built to
work eight hours a day.
packed closer together on the inside tracks (the
packed closer together on the inside tracks (the
higher sector numbers). Therefore the higher
sectors' numbers are usuallyy thee first to fail onn a
slow drive. These facts about slow and fast drives
slow drive. T hese facts about slow and fast drives
are generallyy true about all soft sectored disk drives,
not just the e Atari 810.
A Program To Test RPM
Program 1I is a listingg of a BASIC program that
you can n use to test the speed of your I' 810 disk drive.
You don't have to know how the e program works to
perform the test, but explanations of both the
BASIC program and the machine language proggram
it creates are given later in this anicle.
article.
Type in the BASIC BAS[C program, being carefullo to
double check the numbers in the data statements.
Save the program by giving it a name like
"D:RPMTEST". Then, T with any formatted diskette
in the disk drive. drive, RUN the program.
The program reads sector one onceo each time
the diskette spins around. It allows the drive to get
up to speed, then reads sector one 100 times. This
takes about 20 seconds. TheT elapsed time it takes
the drive to turn 100 revolutions is clocked and the
RPM is computed and printed out.
At Quality QI1ali Software, we judge the outcome of
the RPM test as follows:
RPM
CONCLUSION
under285
too slow
285-290 285·290
OK, don'tadjusl
adjust
over290
too fast
TheT RPMTEST program should be accurate
within plus or minus one RPM. . If you )'OU run the
program several times and get results that vary by
more than one RPM, it may be due to one or both
of the following owing problems which affect drive