Chaotic, but here are some potentially relevant factoids
concerning both diskette drives and the actual diskettes
that go in them.
Diskette drive problems, contamination, etc.
Damaged 3.5" Diskette Drives [internal component damage,
8525 to 8580]
H097490 2.88 MB
Diskette Drive Problem Determination [1MB and 2MB scratch
H096993 PS/2 or VP
Diskette Drive Failures [ZERO_DMA.SYS, pre-DOS 6.0]
up registers after DMA test during POST
Diskette Compatibility [floppy thickness and coating]
Drive Bus Adapter Causes Various Errors/Symptoms 
H037906 System Update Diskette
Ver 1.02 Now Available [DASDDRVR.SYS ver 1.56]
a book [need to research] More human readable...
3.5" Diskette Drive Interchange Problem
3.5 inch diskette will not eject from diskette drive
H034911 Diskette & Diskette Drive Format Compatibility
Diskette drive problems, contamination, etc.
PC and PS/2 users may experience diskette drive errors,
damaged diskettes and interchangeability problems due to
contamination and environmental conditions.
Diskette failure primarily results from:
1. Heads collecting dust.
Because the lower head is exposed upward, debris adheres
to it. When the diskette is inserted into the drive, the
same debris crushes against the diskette, possibly
damaging the magnetic coating. It may result in merely a
tiny pock mark. Occasionally, it results in severe
magnetic-coating destruction such as a crush mark,
tearout, scratch, or combination of all three.
In most cases, the position most often used for head load
can be identified; that is, outside cylinders due to
DIRECTORY or FAT table update prior to the last operation
completion and head unload.
2. Magnetic media may have manufacturing imperfections,
contamination problems, or both.
Small, rather isolated, coating protrusions [observable
under a microscope] develop from: 1) surface defects on
diskette MYLAR base material, 2) contaminating particles
sandwiched between MYLAR surface and magnetic coating, or
3) contamination within magnetic coating material itself.
If protrusions are present on a diskette with poor
coating-to-MYLAR bonding, the head could tear loose a
portion of magnetic coating. Some are crushed by head
impact, destroying a small area of diskette recording
surface. Others tear out and may strip magnetic coating
from MYLAR base. In either case, the diskette is
Low-quality diskettes are more likely to have this problem
because they don't undergo the rigid testing required for
high-quality diskettes. Low-quality diskettes are also
susceptible to poor adhesion of the coating to the MYLAR.
Generally, these low-cost diskettes lack a manufacturing
1. Head contamination due to "burnished-on oxide*."
2. Head contamination due to dust and/or particulate
3. Poor quality media, with poor oxide bonding.
4. Poor quality media, with embedded particulate
* Burnished-on oxide, is the oxide and binder residue
which has migrated from the diskette media and firmly
bonded to the read/write heads.
Format failures and diagnostic
Unnecessary FRU replacement has been attributed to poor
quality or damaged media being used during
troubleshooting. Subsequent use of IBM brand media has
resulted in error free diagnostics and successful diskette
formats on drives which had been "failing" previously.
As diskette quality is not obvious by visual inspection,
only IBM brand diskettes should be used to troubleshoot.
Blank diskettes for diagnostic use:
FRU P/N6023450 for 5.25" DSDD (360KB)
FRU P/N6109660 for 5.25" DSHD (1.2MB)
Dusty environments and infrequent
Until recently, it was never fully understood why diskette
drives fail to read environmentally contaminated
diskettes. Failures result from drives becoming
contaminated after cooling air is drawn through the front
panel and expelled out the back. Part of the airflow
impregnates the magnetic read heads within the flexible
Dust, dirt, and fiber particles pick up a minute
electrical charge, which adheres to the recording head
surfaces. Heads are exposed if no diskette is loaded into
the drive; therefore, many particles settle and adhere to
the surfaces of the lower and upper heads.
The head has two rails or contact sliders that come in
contact with the recording surface upon inserting a
diskette. The rails of the upper head are directly
opposite the rails of the lower head. The impact of
inserting a dusty diskette can easily damage heads or
diskette surfaces. Damage results from one of the
A. Tiny pock marks may occur at head impact point due to
contaminating particles being lodged between the head and
diskette surfaces during head load. Light marks are often
seen but usually do not constitute a read or write
problem. Heavy damage marks may be so severe as to damage
the surface enough to interfere with the recording
B. The contaminant sticks to the head long enough to
develop a surface scratch on or into the diskette magnetic
coating. Usually, this results in a circumferential
scratch deep enough or wide enough to adversely affect the
C. The contaminating particle may bond itself to the media
recording surface during head load. The head now bounces
over the area and cannot read or write properly due to the
head-to-diskette gap being too great. Occasionally, if the
contaminant is soft, it may smear out or pull loose
entirely after several revolutions of the diskette,
resulting in recovery of normal recording operations.
Thus, a failing diskette may reformat correctly. The wipe
material liner within the diskette cartridge will pick up
any loose debris.
D. A particle that has bonded itself to the recording
surface may strip the coating from the MYLAR diskette base
if the coating-to-MYLAR bond is weak. This exposes the
MYLAR base and destroys the diskette. This condition is
more often observed on poor-quality, less-expensive
In an area of high dust or particulate contamination and
infrequent diskette drive usage (daily or less), such as a
banking, store system environment or some LAN
environments, the following recommendation should be very
Use an "expendable" diskette and do a directory listing
("dir a: ", etc), prior to inserting a "critical" data
diskette. This "wipes" the heads and minimizes exposure to
contaminants that would damage diskettes and cause errors.
IBM brand media was used in a test of field returned
diskette drives which had initially failed diagnostic
testing. The heads on these drives were contaminated with
By performing repetitive format routines until all errors
were eliminated, these drives were returned to serviceable
Testing Contaminated Diskettes
A six-week "customer simulation" test was conducted in a
lab with a field-returned planar and one of the returned
diskette drives. Both items were contaminated with an
exorbitant amount of dust and dirt that was not removed
for the test. Both the planar and the drive were used as
shipped to the lab.
Ten new IBM 2 MB diskettes were selected, and the
recording surfaces were observed under microscope. Four
diskettes were used to run a daily backup program. The
remaining six diskettes were formatted daily, except
Sundays. This test simulated how systems are often used in
During two weeks in the middle of the test, this procedure
was not followed. However, during the entire six weeks,
the test system was used daily for formatting other
diskettes and for general lab use. The system was powered
down approximately 50 percent of the time when not in
At the conclusion of the test, the diskettes were again
inspected under the microscope.
During the six-week test, there was absolutely no reason
to suspect any problem with either the planar, the
diskette drive, or any of the diskettes used in this
The 10 controlled test diskettes performed flawlessly.
Re-examination did not disclose any notable changes in the
recording surfaces except for very minute pock marks.
Again, these marks were attributed to contamination
collecting on the lower head, which caused very slight
marks on the diskette surface during head load procedures.
In most cases, it was impossible to identify the head load
area even though it was monitored during the testing.
Field-returned diskette failures result from two factors:
• Large-scale use of media of questionable quality.
• Operation of the computer system in a
less-than-desirable environment; that is, extremely dusty
1. Leave a blank diskette inserted into the diskette drive
when the PC is not in use. This will reduce contamination
from dust particles that collect on heads during inactive
2. To reduce diskette failures, use only high-quality
3. Relocate systems operating in a dusty or dirty
environment, or replace them with a system designed and
rated for industrial use. Avoid placing system units near
Diskettes should operate with no problems in a clean
New diskette products can better withstand contamination.
Improvements being introduced, such as soft head load and
restricted airflow, increase drive/diskette contamination
tolerance. All of these improvements result in better
diskette/drive performance under the same adverse
The use of "head cleaning kits" on PC and PS/2 5.25 and
3.5 inch diskette drives is not supported. Engineering
investigations into "cleaning" of diskette drives have
shown no currently available method to be acceptable.
Should this situation change due to continuing review,
this retain tip will be updated with the appropriate
During the second quarter of 1993, an engineering
review of the use of "head cleaning kits" on PS/2 diskette
drives revealed the following facts:
Due to recent environmental
issues, FREON based solvents, used in some diskette drive
cleaning kits, have been eliminated and replaced with
Isopropyl Alchohol. This exposes the user to the
1. Freon evaporates faster then Isopropyl Alcohol.,
therefore, a user can put too much fluid on the cleaning
disk which will leave a liquid on the head surface.
If a data diskette is then immediately inserted and the
heads are loaded, the magnetic recording surface under the
head can be dissolved.
2. Unlike FREON, Isopropyl Alcohol, as it dries, can leave
a film on the heads. Any film on the head surface can
cause read problems.
The use of quality media, such as that supplied by
IBM, awareness of the "dust" factor and use of the
"expendable diskette" circumvention technique, as
described above, is the best long term solution to gaining
the best reliability from diskette drives.
Damaged 3.5" Diskette Drives [8525-8580]
Incorrectly inserting diskettes into a 720KB or 1.44MB
3.5" diskette drive can leave the drive permanently
damaged and inoperable.
The internal components of the drive, particularly the
mechanism that opens the metal sliding door of a 3.5"
diskette, will be bent if the diskette is inserted
backward or upside-down.
Note: RETAIN tip only
mentions Models 25, 30, 50, 60, 70, and 80
2.88 MB Diskette Drive Problem Determination
[1MB / 2MB scratch disk OK]
When running diagnostics on a 2.88 MB diskette drive,
using a 1 or 2MB diskette will test all drive components
and associated electronics. When running diagnostics, use
an IBM diskette to verify failures before replacing
In some cases, unnecessary FRU replacement has been
attributed to poor quality or damaged media being used
during troubleshooting. Subsequent use of IBM brand media
has resulted in error free diagnostics and successful
operation of diskette drives which had been "FAILING"
For additional information about diskette drives, see
PS/2 or VP Diskette Drive Failures [ZERO_DMA.SYS,
ZERO_DMA Cleans up registers
after DMA test during POST
In all PS/2 or Valuepoint systems with EMM386 installed,
the diskette drive fails to read, write, or format. The
failures may be intermittent or solid and the diskette
drive diagnostics run without error.
If the system configuration allows, remove [REM out] the
EMM386 driver. If failures continue after removing EMM386,
follow normal problem determination methods. If EMM386
cannot be removed for testing, install ZERO_DMA.SYS.
If the diskette drive functions correctly after removing
EMM386, install ZERO_DMA.SYS. Copy it to the root
directory, and add it as the first line in the CONFIG.SYS
file. If this is not possible, place it before any other
If diskette drive failures continue, return to normal
Note: -This problem
was corrected in DOS 6.0 - other memory manager software
which operates similar to EMM386 may also require
Function of DMA_ZERO.SYS
It does not use any memory, and merely performs some
initialization of the DMA hardware to keep EMM386 (and
possible other memory managers) from getting confused by
the values left in the registers after POST's DMA tests.
If EMM386 loads first, you get "Cannot adjust DMA
registers, already in a VM86 session"
Unsure, maybe DOS version? "Cannot adjust DMA registers,
Diskette Compatibility [floppy thickness
* 1.0MB (2HC) diskettes should only be formatted to 720KB
using either 720KB or 1.44MB diskette drives. 1.44MB
diskette drives have "1.44" printed on the eject button.
no printing on the eject button indicates a 720KB diskette
* DOS FORMAT Ver 3.3 and above defaults to 1.44MB format
on a 1.44MB diskette drive regardless of diskette type
being used. To format a 1MB diskette to 720KB on a 1.44MB
drive, the DOS FORMAT command is FORMAT /N: 9/T: 80
The 1MB and 2MB diskettes have different characteristics:
1) Magnetic particle used in the coating ink is
2) 2MB diskette coating thickness is much thinner
than the 1MB diskette.
3) Coercivity [ability to maintain magnetic
information] varies from 1MB to 2MB diskettes.
2MB diskettes are physically thinner than 1MB diskettes.
The 1MB format writes at a higher write current;
therefore, if you tried to format a 2MB diskette in the
1MB mode you could write through one side of the diskette
to the other.
* 2.0MB (2HD) diskettes should be formatted to 1.44MB
using a 1.44MB diskette drive.
* 2.0MB diskettes should not be formatted a in a 720KB
drive -OR- used in a 720KB diskette drive.
* When transferring diskettes between computers that have
720KB and 1.44MB diskette drives, use only 1.0MB capacity
diskettes formatted to 720KB.
* Many application programs contain diskette copy
procedures that allow a backup only to a diskette of the
same capacity as the original diskette.
Drive Bus Adapter Causes Various Errors/Symptoms
The 8550 diskette drive bus adapter
can cause various problems if the copper lands become
exposed and short out against the support structure.
1) Fixed disk light stays on
when fixed disk is not operating.
2) External drive errors when
no external drive exists.
3) 652 errors when running
4) 162 errors
Other errors depend on which signal lines are shorted.
These errors can be solid or intermittent.
First ensure diskette bus adapter card is fully seated.
Inspect bus adapter card for exposed lands where the
card may contact support structure (in some cases the
problem could be internal and not visible to the eye).
Tape may be placed on exposed area to
see if symptom goes away. If so, replace the card.
Note: Any wire clamp
[installed for shipping] that holds the card in place
may be removed by pulling the bottom of the clamp
towards the rear of the system. Chances are vanishing
small that your 8550 still has this shipping clamp,
3.5" Diskette Drive Interchange Problem
Some 8550, 8560 and 8580 systems may require a
replacement 3.5" diskette drive (1.44 MB) for diskette
interchangeability problems between 720 KB diskette
drives and 1.44 MB diskette drives.
To isolate problems with transferring data on 720 KB
3.5" diskettes between the PS/2 8530, PC Convertible,
4865 External 3.5" diskette drive or PC AT/XT internal
3.5" diskette option, and the PS/2 Models 50, 60, or 80.
1. Verify only 3.5" diskettes labeled "DOUBLE SIDED" or
"1.0 MB" were used in the PS/2 Model 30, PC Convertible,
4865 external 3.5" and PC AT/XT 3.5" drive.
2. Verify that 3.5" double sided diskettes were
formatted correctly. The DOS commands are:
PS/2 Model 30, PC Convertible, PC AT/XT and 3.5"
external drives: "FORMAT A: " (A: represents logical
PS/2 Models 50, 60, 80: "FORMAT A: /N: 9/T: 80" (A:
represents logical drive designation)
3. Some customers have reported problems with reading
"DOUBLE SIDED" or "1.0 MB" diskettes in a PS/2 Model 30,
PC Convertible, PC AT/XT or 3.5" external diskette drive
which have been both:
A) Formatted (or written) in a PS/2 Model 30, PC
Convertible, PC AT/XT or external 3.5" diskette drive;
B) Written (or reformatted) by a PS/2 Model 50, 60, or
80 1.44 MB diskette drive.
If a failure of this type is encountered, the following
steps should be taken:
C) First, to recover data, do the following: a new,
blank 1.0 MB DOUBLE SIDED diskette must be formatted in
the PS/2 Model 50, 60 or 80 using the "FORMAT A: /N:
9/T: 80" command.
The diskette which was unreadable can be copied to the
new diskette in the PS/2 Model 50, 60 or 80 using the
DOS COPY command. The new diskette will now be fully
interchangeable between the PC Convertible, PC AT/XT,
3.5" external diskette drive, PS/2 Model 30 and PS/2
Models 50, 60 or 80.
D) Second, if the 1.44 MB diskette drive (FRU P/N
72X8523) in the PS/2 Model 50, 60 or 80 has a sticker in
the lower left rear corner, labeled D01, D02, D03, D04
or D05, and a bar code label beginning with "B1BAO", it
should be replaced.
3.5 inch diskette will not eject from diskette drive
If a 3.5" diskette is inserted upside-down into a
diskette drive and then excessive force is used to fully
insert the diskette, the diskette's metal slide may be
bent, forced off its track, or no longer attached. If a
diskette with a damaged metal slide is inserted, the
slide may catch within the drive and not allow the
diskette to eject properly.
Some diskette drives have a mechanism that does not
allow a diskette (upside-down) to be inserted far enough
to be damaged as described above. However, this will not
stop a diskette, once damaged, from not ejecting
properly from this type drive.
Carefully remove stuck diskette from drive. Once
removed, use advanced diagnostics and a good diskette to
test the drive.
Inspect and replace all damaged diskettes.
If it is necessary to copy a damaged diskette, remove
the damaged metal slide, copy the diskette and then
discard the damaged diskette.