Floppy Drives - wiki.apple2.org

Floppy Drives

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Apple ][ Floppy Drive Reference

A2 5.25 Drives (20 Pin) 20 Pin - Internal Connected Drives
A2 5.25 Drives (19 Pin) 19 Pin - External Connected Drives
A2 3.5 Drives Apple II Specific 3.5" Drives
3.5 Drive Compatibility Chart
A2 Floppy Controllers Internal Cards

Daisy Chain explained

The term daisy chain is where each device in a system plugs into the previous device, thus eliminating the need for additional interfaces. Each device contains a connector to plug the next one in. On the back of the Apple UniDisk 5.25", AppleDisk 5.25", Apple UniDisk 5.25" and the AppleDisk 3.5" is a DB-19 Connector identical to the one that the drive is plugged into. In a drive chain on an Apple II Computer, ANY 3.5" device(s) must always come before any 5.25" device(s)

Other things that use daisy chaining on the Apple are SCSI hard disks and AppleTalk (LocalTalk) networking and Ethernet networking. Although Ethernet and AppleTalk to don't quite 'look' the same, it's still a daisy chain system.

35 vs. 40 or more tracks

The default capacity on Apple 5.25" DSDD floppy storage is 35 tracks, 16 sectors per track. Some drives, including most of what Apple offers are actually capable of 48 tracks per inch. There are mods for DOS 3.3 to make it format up to 40 tracks, but keep in mind, these disks may not work in another drive. If there is a problem it is usually within the last 5 tracks, the additional ones, that can't be read as they are beyond the normal range. However this is usually only the earliest 5.25" drives as the industry standard was 48 tracks per inch. For clarification, the track layout on all drives is identical, the 'extras' are added to the end, the spacing, layout, beginning on the disk, etc- does not change.

13 vs. 16 Sectors per Track

When the Apple Disk ][ was first offered it was 13 sectors per track. Shortly after introduction this was increased to 16 sectors. Apple used to provide little round stickers that had an Apple logo silhouette in red with a '16' on white type. What Apple should have actually done was provided the same sticker with a '13' for those few disks you would have left over, not for all the new ones you were going to format.

DOS 3.3 Maximum Capacity

The largest volume size Apple DOS 3.3 can handle without any modification what so ever is 400K. The VTOC (Volume Table of Contents) directly supports up to 400K of tracks/sectors in a 32 sector per track maxim 1) A Modification may be necessary for the DuoDisk to work on a IIgs 2) As noted, certain IIc Plus+ units seem to work with any version of the 19 Pin 5.25 drive, and do not require the 'platinum drive'

720K ProDOS Volumes

If you have an DSDD (Double Density) 3.5" MFM drive via a PC Transporter, Blue Disk or Urphi controller, you can format 720K disks as ProDOS volumes. These disks CAN NOT be read in ANYTHING that is 800K only with exception of an AppleDisk 3.5" hooked up to a PC Transporter. If it's an Apple or compatible 800K drive hooked to ANYTHING other than a PC transporter you CAN NOT READ THESE 720K DISKS. They are MFM. These drives can NOT do MFM with exception of the PC Transporter is doing something specific since it has a hybrid version of the IWM integrated with it.

Blank Media 5.25" / 3.5" Disks

Common Media use by disk size/capacity

Disk Size / Type Capacity Compatible With:
5.25" DSDD 140K Disk ][, DuoDisk, Disk //c, UniDisk 5.25"
AppleDisk 5.25" & Other 5.25" Drives
3.5" SSDD 400K Apple External 400K Drive on UDC / Laser 128
3.5" DSDD 800K AppleDisk 3.5", UniDisk 3.5", AE 3.5" Drive
AMR & Laser 3.5" Drive
3.5" DSHD 1.44MB Apple FDHDSuperDrive, AE 3.5" HD Drive
3.5" DSHD 1.6MB Applied Engineering HD+

Common Media use by Computer

Computer Common Disk Type Alternate / Note
Apple ][+ 5.25" DSDD 3.5" DSDD
Apple //e 5.25" DSDD 3.5" DSDD, DSHD
Apple //c 5.25" DSDD 3.5" DSDD
Apple IIc Plus 3.5" DSDD 5.25" DSDD
Apple IIgs 3.5" DSDD 5.25" DSDD, 3.5" DSHD

Substituting DSHD (1.2MB or 1.44MB) for DSDD (360K or 720K/800K) media. DON'T!

DSHD (High Density) Disks SHOULD NOT BE SUBSTITUTED for DSDD (Double Density) Disks. In simple terms, the density (amount of) magnetic particles on the disk per inch is different for the two disks. That means that the disks are not 'optimized' for other than the format they were designed. While they may work, you WILL loose data, and most likely, WILL loose data over time. The proper disks can be found. You may have to mail order them, but they can be found. Again, you WILL loose data. Thats a promise. It's not a matter of it, but only when.

Other Media Formats

QIC-80 34 pin tape backups are supported by the BlueDisk controller.

There were 8" controller cards made by several companies, 2 of the being Lobo Drives, and Sorrento Valley Associates. Storage on 8" disks in Apple format can be as much as 3 MB.

The AmDisk drive uses 3 (Three Inch) format floppy disks. These disks don't seem to be available anyplace.

Rana, MicroSci and Kodak each made a type of High Density disk drive for use with any slotted Apple II. These drives use industry standard "AT" disks, or 5.25" DSHD disks for capacities up to 1.2 MB per disk.

The MicroSci A80 and Rana Elite 3 drives require High Density disks.

Additional IWM/technical information: http://www.stockly.com/forums/showthread.php?t=9

Drive Head Cleaning

Clean drive heads make a huge difference in drive performance. 95% of problem drives can be fixed with cleaning the read/write head(s). Yes, 95%.

Before you whip out that cleaning disk and the alcohol, consider this. There is a pretty good chance that the heads on that drive you have right there have never been cleaned and as much, that the drive is probably at least 20 years old by now. If a cleaning disk has not been used regularly it's not going to do much good. It may not even make a dent in the issue.

The next sections you will find information of a general nature on cleaning the heads in various types of common drives. 5.25 in. drives will stand up to much more abuse and handling. 3.5 in. drive on the other hand are considerably more fragile.

The methods covered here may seem extreme, but the end result is a squeaky clean drive head. Some purists may cringe at what they are about to read. From my personal experience, I've never killed a drive. Thats about as simple as I can put it.

Disk ][ / 5.25 Full Height Drives


Cleaning the drive head on the Disk ][ and similar drives is actually very easy. The head assembly is very easy to reach, only "6 screws deep", and one connector. The image above is that of a Disk ][ drive with the cover removed. To remove the cover, remove the four screws on the bottom and slide the cover off the drive.

The PCB (Printed Circuit Board) you see on top is called the Analog Card. The Motor control PCB is the smaller one to the rear of the drive assembly. The next thing you need to do is remove the analog card. Start by removing the drive head connection cable. It is the white connector that is toward the front of the Analog Card. To remove the connector, use two fingers and wiggle it toward the front of the drive. It will slide back about 3/8ths of an inch.

Remove the two screws holding the Analog Card in place. One is just next to the connector you just removed and the other is at the other front corner. Slide the Analog card forward to get it out of the notches and then flip it backwards over the rear of the drive and out of the way.

You should now see the drive door/centering hub assembly. There may be a metal 'lid' over the head assembly. This just snaps down on the sides. Pop it off by lifting one side, then the other.

The drive head assembly will have a pressure pad on a hinged spring loaded lever that is lifted out of the way when the drive door is opened, and when the drive door is closed it is lowered onto the disk and this keeps positive pressure on the moving media so that it maintains constant contact with the head. The label is actually on the opposite side of the disk than the data. In the case of a double sided drive, instead of the pressure pad you would find another head that would by default also act as the pressure pad.

The exception to this would be the Apple FileWare ('Twiggy') drive that was offered in the Lisa computer at time of introduction. It's heads were horizontally opposed and thus each has it's own pressure pad. This allowed the FileWare drive to simultaneously read/write on both sides of the disk for increased performance. An image of the Twiggy Drive / Diskette is shown below.


Just lift the pressure pad and you will see the drive head.

The head should be shiny like glass, white with a small black dot or slash in the middle.

What you will probably find is a black or brown blob which represents years of use built up on the head. If it's brown then it's disk particles from deteriorating disks. This is especially hard for the cleaning disk to ever get off. You could let that spin for days and it would never do a thing to it.

The disk head is made of glass and is very dense. When someone asks me how to clean a drive head, I generally say "spit shine it" and I'm not kidding. I open up the drive and get down to the head, lick a finger and rub on the head, take a shirt tail and wipe it off. Done. Don't be afraid, there's nothing you can do to that head with your finger thats going to harm it. Sometimes that buildup on there can be pretty stubborn and you can be convinced it really belongs there. It does not. That surface should be mostly white and any black you see should be absolutely centered and below the surface.

Again, this is why the cleaning disk will never work and in some ways it's worse, if the cleaning disk is setup for a double sided drive and you place it in a single sided drive- it can tear up the pressure pad and then the drive will have a harder time working.

The head is very durable. The surface of a disk may look smooth, but it's actually super fine magnetic particles. In effect, it's sand paper. The disk head has to put up with this constant friction so it can't be made out of anything that is going to wear down. The disk itself is the weak link in this equation.

You can use Bounty and alcohol, Q-tips and alcohol, etc, too. It needs to be clean and shiny. If it's really bad it will harm disks.

When thats all clean- put the analog card back, plug in the head connector and test it out.

Other 5.25 in. drives

Other drives that use a full height assembly are usually very similar in make up. Half height drives made up around the Alps assembly like the Apple //c internal / External drive, the Unidisk/Duodisk 5.25 and AppleDisk 5.25 are very similar as well and the same instructions without the image generally work. On some of these the pressure pad may not lift much farther off the head meaning you can't see straight down at it, in this case- Q-Tips and alcohol are generally the way to go.

3.5 in. Drives

Cleaning 3.5 in. drive heads can usually be accomplished with the cleaning disk with far far more success than the 5.25 in. drives.

But in those cases where it's not working, the concept is similar but you may need to take apart less or far more to get to the heads themselves.

But .... read on:

3.5 in. drives are generally FAR MORE fragile than 5.25 in. drives.

I'll say it again. 3.5 in. drives can be far more susceptible to damage by handling.

3.5 in. drive also don't generally get as bad as 5.25 in. drives because the disks are shuttered. But should you need to clean heads..


I can tell you for a fact that most double sided 3.5 in. drives will not work again if you simply reach down and lift up that drive head. They are made of tensioned brass or copper sheeting and not a spring that just snaps back. They will actually bend and not go back when you let go. The image above is of one side of a typical 3.5 in. drive head.

Now I have been able to re-tension most of these when thats all that has happened, but the same way those are made, the heads themselves are actually floating on tensioned thin metal. That means if you push down on them extensively, they will most likely come out of alignment. Disk drives are all about alignment - that way they are all .. "on the same track".

As you can gather from the image above, some due diligence is in order when handling 3.5 in. drive heads. Alcohol and Q-tips are generally the best to use and with one hand only.

Do not re-use the Q-tip, dip it once, put it in, twirl it around a few times, take it out and look at it. Turn it around and do it again. Do not re-use them because it will start to have threads hanging off and those can get caught on the head and when you pull it out, by the time you feel the tension and stop- it's probably too late. You've already pulled the head.

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