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 40 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 40 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.

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

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