FDD Problems
Chaotic, but here are some potentially relevant factoids concerning both diskette drives and the actual diskettes that go in them.

H09135 Diskette drive problems, contamination, etc.  
H031798 Damaged 3.5" Diskette Drives [internal component damage, 8525 to 8580]
H097490 2.88 MB Diskette Drive Problem Determination [1MB and 2MB scratch disk OK]
H096993 PS/2 or VP Diskette Drive Failures [ZERO_DMA.SYS, pre-DOS 6.0]
   ZERO_DMA Cleans up registers after DMA test during POST
H02694 Diskette Compatibility [floppy thickness and coating]
H025645 Diskette Drive Bus Adapter Causes Various Errors/Symptoms [8550]
H037906 System Update Diskette Ver 1.02 Now Available [DASDDRVR.SYS ver 1.56]
  DASDDRVR  From a book [need to research] More human readable...
H12392 3.5" Diskette Drive Interchange Problem 
H096794 3.5 inch diskette will not eject from diskette drive

H09135 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 destroyed.

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 brand.

To summarize:
1. Head contamination due to "burnished-on oxide*."
2. Head contamination due to dust and/or particulate matter.
3. Poor quality media, with poor oxide bonding.
4. Poor quality media, with embedded particulate contaminants.

* 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 errors:
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 usage:
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 media drive.

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 following:

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 process.

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 recorded signal.

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 diskettes.

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 helpful:

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.

Additional information:
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 "burnished-on" oxide.

By performing repetitive format routines until all errors were eliminated, these drives were returned to serviceable condition.

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 the field.

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 direct use.

At the conclusion of the test, the diskettes were again inspected under the microscope.

Test Results
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 system.

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.

Conclusions
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 conditions.

Recommendations
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 periods.

2. To reduce diskette failures, use only high-quality media.

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 carpeting.

Diskettes should operate with no problems in a clean environment.

Summary
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 operating conditions.

Cleaning Kits  
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 information.

 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 following situations:

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.

H031798 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

H097490 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 diskette drive.

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" previously.

For additional information about diskette drives, see RETAIN H09135.


H096993 PS/2 or VP Diskette Drive Failures [ZERO_DMA.SYS, pre-DOS 6.0
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 device drivers.

DEVICE=ZERO_DMA.SYS

If diskette drive failures continue, return to normal problem determination.

NOTE: -This problem was corrected in DOS 6.0 - other memory manager software which operates similar to EMM386 may also require ZERO_DMA.SYS .

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, incorrect system"


H02694 Diskette Compatibility [floppy thickness and coating]
* 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 drive.

* 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 different.
 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.



H025645 Diskette Drive Bus Adapter Causes Various Errors/Symptoms [8550]

The 8550 diskette drive bus adapter can cause various problems if the copper lands become exposed and short out against the support structure. Possible errors:

     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 diagnostics.
     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, but...


H12392 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 drive designation)

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; and,

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.

H096794 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.

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