Apple SuperDrive
| Apple SuperDrive | |
|---|---|
 |
|
| Apple SuperDrive / FDHD Drive | |
| Manufacturer | Apple Computer, Inc. (Sony mechanism) |
| Type | Floppy disk drive |
| Interface | DB-19 external floppy port |
| Compatible | Macintosh models with a SWIM controller |
| Predecessor | Apple 3.5 Drive |
| Model | G7287 |
The Apple FDHD drive, marketed as the SuperDrive, is Apple's high-density 3.5-inch floppy drive. Apple's own description: storage capacities of 400K, 800K and 1.4 MB, and it can read and write MS-DOS files in addition to standard Macintosh files.[1]
Apple consistently calls the capacity 1.4 MB, not 1.44 MB.[1]
Formats
| Disk type | Capacity | File system | Encoding |
|---|---|---|---|
| 3.5-inch single sided | 400 KB | MFS | Apple GCR |
| 3.5-inch double sided | 800 KB | HFS | Apple GCR |
| 3.5-inch double sided | 720 KB | MS-DOS | MFM |
| 3.5-inch high density | 1.4 MB | HFS | Apple GCR |
| 3.5-inch high density | 1.4 MB | MS-DOS | MFM |
Read that table carefully. The Macintosh 1.4 MB format uses Apple GCR, not MFM. Only the MS-DOS formats use MFM. Descriptions giving the Macintosh high-density format as "GCR/MFM" or as MFM are wrong by Apple's own table.[1]
The two encodings differ in one rule. Under GCR with NRZI, a transition always occurs for a one and none for a zero, and the driver formats each three data bytes as four 8-bit patterns so that more than two adjacent zeros never occur. Under MFM, a transition always occurs for a one, none for an isolated zero, and a transition always occurs for two adjacent zeros.[1]
SWIM
The controller is the SWIM (Super Woz Integrated Machine). It controls four of the disk state-control lines, generates the internal/external drive-select signals and the read- and write-data signals; the VIA provides a fifth state-control line.[1]
- The SWIM clock is 15.6672 MHz — twice the IWM's. During startup, software sets a bit in the SWIM to divide the clock by two when reading and writing to an 800K drive or a Hard Disk 20.[1]
- On the Macintosh IIfx the SWIM is driven by the IOP custom IC, which moves disk data between main memory and its own dedicated RAM by DMA.[1]
- The SWIM does not support the single-sided floppy disk drive.[1] That is the reason a 400K drive does not work on an FDHD machine, and it is a hard limit, not a software one.
Maximum rate to the drive is approximately 500 kbit/s, and approximately 375 kbit/s effective in GCR mode.[1]
Compatibility
| Model | Internal | External |
|---|---|---|
| Macintosh SE FDHD | 1 | 1 |
| Macintosh SE/30 | 1 | 1 |
| Macintosh Portable | 1 or 2 | 1 |
| Macintosh IIx | 1 or 2 | 0 |
| Macintosh IIcx | 1 | 1 |
| Macintosh IIci | 1 | 1 |
| Macintosh IIfx | 1 or 2 | 0 |
Macintosh SE computers made before September 1989 use the 800K drive; FDHD machines are marked FDHD on the front.[1]
On any model that supports an external FDHD drive you can connect an external 800K drive instead[1] — but not the other way round for single-sided drives, which the SWIM does not support at all.
Internal Connectors
These designators come from Apple's own take-apart and are what you will be reconnecting:[2]
| Connector | Goes to |
|---|---|
| CN101 | External drive cable |
| CN102 | Daisy-chain interface board |
| CN104 | LED cable |
| CN105 | Eject button cable |
Disassembly
Apple's procedure, abbreviated:[2]
- Remove the four screws from the case bottom and pull the bottom cover off.
- Remove the floppy metal shield from the drive assembly.
- Pull the cable anchor free of the top case.
- Grip the case top in one hand and the drive assembly in the other, slide the assembly as far as it will go towards the cable end, and lift it out. Flip it over.
- Using needle-nose pliers, disconnect CN104 (LED) and CN105 (eject button).
- For the external cable: remove the mounting screw from the external drive shield, gently pull the shield back and disconnect the cable from CN101. If you are replacing either the shield or the cable, separate them first by removing the ground screw.
- For the daisy-chain board: disconnect CN102, pull back the two side tabs to remove the plastic daisy-chain cover from the outer metal shield, then remove the screw holding the board and slide it out to the right.
Replacement note, and it is easy to miss: before installing a replacement 1.4 MB SuperDrive mechanism, you must remove the dust shield.[2]
Troubleshooting
Apple's symptom chart, in Apple's order — try the first cure first, and if it does not fix the symptom reinstall the original module before moving on:[2]
| Symptom | Sequence |
|---|---|
| Drive does not come on; LED flashes once or does not light | Drive mechanism → external drive cable → LED assembly |
| Reads but does not write | Drive mechanism → external drive cable |
| Does not read but LED comes on | Bad disk → drive mechanism |
| Does not eject disk | Drive mechanism → eject switch cable assembly |
| Functions, but LED does not light | LED assembly → drive mechanism |
| Reads/writes 800K disks but not HD disks | Verify that the drive is a 1.4 MB SuperDrive → drive mechanism |
| Unable to read; many file-transfer errors | Clean drive → drive mechanism |
| Fails to format | Clean drive → drive mechanism |
| An MS-DOS drive does not recognise a disk formatted on a 1.4 MB SuperDrive | Format all disks on the MS-DOS drive first, then read and write them with either |
Two of those entries are worth extracting.
"Reads 800K but not HD"
Apple's first step is not a repair at all — verify that the drive actually is a 1.4 MB SuperDrive.[2] An 800K mechanism in a SuperDrive-era case looks identical from the outside. Related, and equally not a fault: a SuperDrive on a machine with an IWM rather than a SWIM cannot do high density, because the controller, not the drive, is the limit.[1]
The MS-DOS exchange rule
To read and write files with both an MS-DOS drive and a 1.4 MB SuperDrive, format all disks on the MS-DOS drive first.[2] This is Apple's own workaround and it converts an apparently intermittent cross-platform problem into a one-line procedure.
Head cleaning
Apple's charts start "clean drive" for read errors and format failures.[2] Use a 3.5-inch head-cleaning disk and do not overdo it — cleaning wears heads.
What Is Not Documented
No Apple figures for the external SuperDrive's release date, retail price, discontinuation date, dimensions, weight or transfer rate as a product could be traced, and none are stated here. The "SWIM" expansion as "Sander–Wozniak Integrated Machine" is a community backronym; Apple's own text gives it as Super Woz Integrated Machine.[1]
Apple's service manual for this drive
Apple's own manual is the Apple SuperDrive volume of Service Source, hosted here as Apple SuperDrive/HDI-20 Service Source. It covers the external 1.4 MB SuperDrive and the HDI-20, and it is the only Apple external floppy drive volume that carries a symptom chart: it maps "drive reads but does not write", "does not eject", "functions but LED does not light" and the rest to specific replacements, and it records two behaviours that are not faults - an MS-DOS machine refusing a disk formatted on a SuperDrive, and an 800K drive mistaken for a SuperDrive because it will not take high-density media.[3]
See Also
References
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 Guide to the Macintosh Family Hardware, second edition, Apple Computer, Inc. / Addison-Wesley, 1990 — hosted on this wiki as File:Apple Guide to the Macintosh Family Hardware 2nd Edition 1990.pdf. Chapter 9, "Floppy Disk Interfaces": the description of the 400K drive as a single-sided version of the Apple 800K drive; Table 9-1, drive type against disk type, capacity, file system and encoding method; the GCR/NRZI and MFM encoding rules; Tables 9-2 and 9-6, which Macintosh models take which drive and how many internal and external drives each supports; the IWM and SWIM interface ICs, their C8M (7.8336 MHz) and C16M (15.6672 MHz) clocks, the maximum data rate of approximately 500 kbit/s and the effective GCR rate of approximately 375 kbit/s; Figure 9-3 and Tables 9-3 and 9-4, the 20-pin internal connector pinouts; Figure 9-4 and Table 9-5, the DB-19 external connector pinout; the warning that all devices connected to a Macintosh Plus must not draw more than 600 mA at +12 V, 700 mA at +5 V and 10 mA at −12 V, that a single-sided floppy drive requires 500 mA at +12 V and 500 mA at +5 V and that an Apple 800K drive requires 600 mA at +12 V and 360 mA at +5 V; the PWM motor-speed-control line, used only by 400K single-sided drives and generated by a PAL on the Macintosh Plus and the BBU on the Macintosh SE from values in the disk-speed buffer in RAM, with the statement that the 800K drive controls its own motor speed and ignores the signal; the statement that the SWIM does not support the single-sided floppy disk drive; the statement that an external 800K drive may be connected to any model that supports an external FDHD drive; and the Hard Disk 20 pass-through arrangement, whose DB-19 pinout is identical to the computer's.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Apple SuperDrive Service Source, Apple Computer, Inc. — hosted on this wiki as File:Apple superdrive.hdi 20.pdf. Troubleshooting symptom charts (drive does not come on and the LED flashes once or does not light; reads but does not write; does not read but LED comes on; does not eject; functions but LED does not light; MS-DOS drive does not recognise a disk formatted on a 1.4 MB SuperDrive; reads and writes 800K disks but not HD disks; unable to read with many file-transfer errors; fails to format). Take Apart: four screws in the case bottom, the floppy metal shield, the cable anchor, and the connector designators — CN101 external drive cable, CN102 daisy-chain interface board, CN104 LED cable and CN105 eject button cable — together with the daisy-chain interface board and 1.4 MB mechanism procedures and the replacement note that the dust shield must be removed from a replacement mechanism before installation.
- ↑ Apple SuperDrive, Apple Service Source, 21 pages, PDF distilled 21 November 1995 - hosted on this wiki as Apple SuperDrive/HDI-20 Service Source, file File:Apple superdrive.hdi 20.pdf. Troubleshooting symptom charts and the Take Apart order (top and bottom cover, external cable and shield, daisy chain interface board, 1.4 MB drive mechanism, eject switch assembly, LED assembly). The manual has no Specifications chapter, so no current draw or seek time for the external SuperDrive is printed in it.