Apple 400K Drive: Difference between revisions
Fix image syntax to File:... |
Rebuild from Guide to the Macintosh Family Hardware ch.9 + the Apple 400K Drive Service Source already hosted here but unused. Connector is DB-19 not DE-19. Sourced the SE-FDHD incompatibility to Apples own statement that the SWIM does not support single-sided drives, and documented the PWM host-generated motor-speed line that is the real reason. Added drive current requirements and the Mac Plus power budget, the DB-19 pinout and Apples six-screw take-apart. Deleted unsourced May 1984 date, U... |
||
| Line 4: | Line 4: | ||
| manufacturer = Apple Computer, Inc. (Sony mechanism) | | manufacturer = Apple Computer, Inc. (Sony mechanism) | ||
| type = Floppy disk drive | | type = Floppy disk drive | ||
| interface = DB-19 external floppy port | |||
| compatible = Macintosh 128K, 512K, 512Ke, Plus, SE (pre-FDHD) | |||
| interface = | |||
| compatible = Macintosh 128K, 512K, 512Ke, Plus | |||
| successor = [[Apple Floppy Disk Drive|Macintosh 800K External Drive (M0131)]] | | successor = [[Apple Floppy Disk Drive|Macintosh 800K External Drive (M0131)]] | ||
| model = M0130 | | model = M0130 | ||
}} | }} | ||
<templatestyles src="Template:StyledTable/styles.css" /> | |||
The '''Macintosh External Disk Drive''' (model M0130) is Apple's single-sided 400 KB external 3.5-inch floppy drive for the first Macintosh models. Apple describes it not as a separate design but as '''"a single-sided version of the Apple 800 KB drive"'''.<ref name="gmfh9">''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.</ref> | |||
== Format == | |||
== | {| class="wikitable styled-table" style="width:85%;" | ||
|+'''Apple Table 9-1, the 400K line'''<ref name="gmfh9" /> | |||
! Disk type !! Capacity !! File system !! Encoding | |||
|- | |||
| 3.5-inch single sided || 400 KB || MFS || Apple GCR | |||
|} | |||
Apple GCR uses NRZI encoding, in which a transition always occurs for a one in the data stream and no transition for a zero. Groups of three or more zeros would be hard to distinguish, so the disk drivers format data so that more than two adjacent zeros never occur: '''each group of three data bytes is formatted as four 8-bit patterns'''.<ref name="gmfh9" /> That four-for-three expansion is why the effective data rate is lower than the raw one — see below. | |||
The | == The Speed Control Line: What Makes This Drive Different == | ||
'''This is the single most important technical fact about the 400K drive, and it explains nearly all of its compatibility limits.''' | |||
The 400K drive '''does not control its own motor speed'''. It requires a '''pulse-width-modulated (PWM) signal''' from the computer to do so. A general logic IC — a PAL in the [[Macintosh Plus]], the BBU in the [[Macintosh SE]] — generates that signal from values it reads out of the disk-speed buffer in RAM. By running the disk motor at slower speeds the computer can store more sectors in the tracks nearer the edge of the disk.<ref name="gmfh9" /> | |||
The | |||
By contrast, '''the 800K drive controls its own motor speed and ignores the speed-control signal'''.<ref name="gmfh9" /> | |||
== | Two consequences follow directly: | ||
* On the Macintosh SE the speed-control signal is available '''only for the 400K external drive''', not for internal drives.<ref name="gmfh9" /> | |||
* '''The Macintosh II has no external floppy connector and no disk-speed control line at all''', so it cannot use this drive.<ref name="gmfh9" /> | |||
Apple adds a developer warning that is worth repeating because copy-protection schemes of the era ignored it: '''because some drives ignore the speed-control signal, applications should never depend on it.'''<ref name="gmfh9" /> | |||
== Compatibility == | |||
{| class="wikitable" | {| class="wikitable styled-table" style="width:80%;" | ||
|- | |+'''Machines that use the 800K-family drives''' (Apple Table 9-2)<ref name="gmfh9" /> | ||
! | ! Model !! Internal drives !! External drives | ||
|- | |- | ||
| | | Macintosh Plus || 1 || 1 | ||
|- | |- | ||
| | | Macintosh SE (before the FDHD change) || 1 or 2 || 1 | ||
|- | |- | ||
| | | Macintosh II || 1 or 2 || '''0''' | ||
|} | |} | ||
''' | On the Macintosh Plus and the SE the external connector will take '''an 800K drive, a single-sided 400K drive, or an Apple Hard Disk 20'''.<ref name="gmfh9" /> | ||
== | === Why it stops working on later machines === | ||
The reason is stated plainly in Apple's own documentation: '''"The SWIM does not support the single-sided floppy disk drive."'''<ref name="gmfh9" /> | |||
400K | The SWIM is the controller in the Macintosh SE FDHD and everything after it. So a 400K drive on an SE FDHD, SE/30, IIx, IIcx, IIci, IIfx or Portable will not work, and this is a designed-in limitation rather than a fault. Apple dates the SE change to '''September 1989''' in one place and describes machines made '''after August 1989''' as having the FDHD drive in another; FDHD machines are identified by the letters '''FDHD''' on the front.<ref name="gmfh9" /> | ||
== Connector == | |||
= | The external connector is a '''DB-19''' — Apple's own designation.<ref name="gmfh9" /> | ||
== | {| class="wikitable styled-table" style="width:75%;" | ||
|+'''DB-19 external floppy connector''' (Apple Table 9-5)<ref name="gmfh9" /> | |||
! Pin !! Signal !! Pin !! Signal | |||
Apple | |||
! | |||
|- | |- | ||
| | | 1–4 || GND || 12 || PH1 (state-control line) | ||
|- | |- | ||
| | | 5 || −12 V || 13 || PH2 (state-control line) | ||
|- | |- | ||
| | | 6 || +5 V || 14 || PH3 (Register Write Strobe) | ||
|- | |- | ||
| | | 7–8 || +12 V || 15 || /WRREQ (Write Data Request) | ||
|- | |- | ||
| | | 9 || n.c. || 16 || SEL (state-control line) | ||
|- | |- | ||
| | | 10 || '''PWM''' (motor-speed control) || 17 || /ENBL.EXT (External Drive Enable) | ||
|- | |- | ||
| | | 11 || PH0 (state-control line) || 18 || RD (Read Data) | ||
|- | |- | ||
| | | || || 19 || WR (Write Data) | ||
| | |||
| | |||
|} | |} | ||
= | '''Pin 10, PWM, is the line this drive depends on and the 800K drive ignores.'''<ref name="gmfh9" /> | ||
=== Current draw === | |||
Apple gives real numbers, which makes a power-related fault diagnosable:<ref name="gmfh9" /> | |||
* '''A Macintosh single-sided floppy disk drive requires 500 mA at +12 V and 500 mA at +5 V.''' | |||
* An Apple 800K drive requires 600 mA at +12 V and 360 mA at +5 V. | |||
* '''The combined load of all devices connected to a Macintosh Plus must not exceed 600 mA at +12 V, 700 mA at +5 V and 10 mA at −12 V.''' | |||
Note what that means: a 400K external drive on a Macintosh Plus is already drawing 500 of the 600 mA available at +12 V. '''There is no headroom for anything else on that port.''' | |||
=== | === Data rate === | ||
The IWM can send data to the drive at a maximum of approximately '''500 kbit/s'''. Because four bytes of GCR-encoded data correspond to three bytes in system RAM, '''the effective maximum is approximately 375 kbit/s'''. Actual throughput depends on seek time, RAM access and other system tasks.<ref name="gmfh9" /> | |||
=== | === Daisy-chaining === | ||
An Apple Hard Disk 20 plugs into the computer and the external floppy drive plugs into the DB-19 on the back of the Hard Disk 20; '''the pinout of that connector is identical to the computer's'''.<ref name="gmfh9" /> | |||
== Disassembly == | |||
Apple's procedure:<ref name="ss400">''Apple 400K Drive Service Source'', Apple Computer, Inc. — hosted on this wiki as [[:File:Apple 400k drive.pdf]]. Take Apart, "400K Mechanism": six screws in the bottom cover; lift the back of the cover about an inch and pull it out from the front bezel; lift the back of the metal drive housing while supporting the cable connector; remove the cable connector; remove the screw holding the grounding tab; remove the screw on the outside of the metal drive housing and slide the drive out. Plus an exploded view.</ref> | |||
# Turn the drive over, bottom facing up. '''Remove the six screws''' from the bottom cover. | |||
# Lift the back of the cover about an inch and pull it out from the front bezel. | |||
# Lift the back of the metal drive housing — '''supporting the cable connector''' as you do — and remove the drive from the bottom cover. | |||
# Remove the cable connector. | |||
# Remove the screw that holds the '''grounding tab''' in place. | |||
# Remove the screw on the outside of the metal drive housing and slide the drive out of the housing. | |||
The grounding tab screw is the one people miss; the drive will not slide out with it fitted. | |||
== Troubleshooting == | |||
== | === Not recognised on a later Macintosh === | ||
Not a fault. The SWIM does not support single-sided drives.<ref name="gmfh9" /> Test the drive on a Macintosh Plus, an SE made before the FDHD change, or a 128K/512K. | |||
=== Speed errors, or reads fail on outer tracks === | |||
Consider the '''host''' as well as the drive. This drive's motor speed is generated by the computer through the PWM line on pin 10.<ref name="gmfh9" /> A fault in the PAL (Macintosh Plus) or BBU (Macintosh SE) that generates it, or a break in pin 10, produces disk errors that look exactly like a worn mechanism. | |||
=== Will not read at all === | |||
Clean the head with a 3.5-inch head-cleaning disk. The single head is on the '''bottom''' of the mechanism — it is a single-sided drive.<ref name="gmfh9" /> | |||
== | === Will not eject === | ||
Use the emergency eject hole before dismantling anything. | |||
=== | === Intermittent or dead with other devices attached === | ||
Check the power budget above. A 400K drive takes 500 mA of the Macintosh Plus's 600 mA +12 V allowance on its own.<ref name="gmfh9" /> | |||
=== | == What Is Not Documented == | ||
== | No Apple figures for this drive's release date, retail price, discontinuation date, dimensions, weight, rotation speed range or sector-per-zone layout could be traced to a source consulted here, and none are stated. In particular, the "5 zones of 16 tracks", "8–12 sectors per track" and "394–590 RPM" figures that circulate are not in Apple's own chapter, which says only that '''running the motor at slower speeds lets the computer store more sectors in the tracks nearer the edge of the disk'''.<ref name="gmfh9" /> The closely related [[Apple 3.5 Drive]] mechanism '''is''' specified by Apple, and those figures are on the [[Apple Floppy Disk Drive]] page.<ref name="ss35">''Apple 3.5 Drive Service Source'', Apple Computer, Inc. — hosted on this wiki as [[:File:Apple 3.5 drive.pdf]]. Specifications: disk diameter 3.5 in., 2 recording surfaces, 80 tracks per inch; seek time track-to-track 6 ms maximum, settle time 30 ms maximum, drive startup time 600 ms maximum; head position accuracy ±0.035 mm; formatted capacity 800K and unformatted 1,246K, with the note that disks should be certified double-sided media; the list of directly supported computers and the note that one additional drive can be daisy-chained on the Apple IIGS; operating temperature 40–122 °F (5–50 °C), storage ‒40 to 140 °F with no condensation, relative humidity 5–90%; electrical +12 V standby 10 µA, typical 120 mA, peak 600 mA during eject only for a 2-second maximum, and +5 V standby 10 mA, typical 360 mA; size 2.01 × 4.72 × 7.87 in. (51 × 120 × 200 mm) and weight 2.8 lb (1.3 kg). Troubleshooting symptom charts, including the yellow-versus-red logic-board-to-drive cable checks and the CXD1085A/CXD1085B daisy-chain gate-array revision.</ref> | ||
== See Also == | == See Also == | ||
* [[Apple Floppy Disk Drive]] | * [[Apple Floppy Disk Drive]] | ||
* [[Apple SuperDrive]] | * [[Apple SuperDrive]] | ||
* [[ | * [[Macintosh 128K]] | ||
* [[Apple UniDisk 3.5]] | |||
== References == | == References == | ||
<references /> | |||
{{Navbox-AppleVintageAccessories|state=collapsed}} | |||
[[Category:Apple Vintage Accessories]] | [[Category:Apple Vintage Accessories]] | ||
Latest revision as of 19:20, 23 September 2026
| Apple 400K Drive | |
|---|---|
 |
|
| Macintosh External Disk Drive (Model M0130) | |
| Manufacturer | Apple Computer, Inc. (Sony mechanism) |
| Type | Floppy disk drive |
| Interface | DB-19 external floppy port |
| Compatible | Macintosh 128K, 512K, 512Ke, Plus, SE (pre-FDHD) |
| Successor | Macintosh 800K External Drive (M0131) |
| Model | M0130 |
The Macintosh External Disk Drive (model M0130) is Apple's single-sided 400 KB external 3.5-inch floppy drive for the first Macintosh models. Apple describes it not as a separate design but as "a single-sided version of the Apple 800 KB drive".[1]
Format
[edit | edit source]| Disk type | Capacity | File system | Encoding |
|---|---|---|---|
| 3.5-inch single sided | 400 KB | MFS | Apple GCR |
Apple GCR uses NRZI encoding, in which a transition always occurs for a one in the data stream and no transition for a zero. Groups of three or more zeros would be hard to distinguish, so the disk drivers format data so that more than two adjacent zeros never occur: each group of three data bytes is formatted as four 8-bit patterns.[1] That four-for-three expansion is why the effective data rate is lower than the raw one — see below.
The Speed Control Line: What Makes This Drive Different
[edit | edit source]This is the single most important technical fact about the 400K drive, and it explains nearly all of its compatibility limits.
The 400K drive does not control its own motor speed. It requires a pulse-width-modulated (PWM) signal from the computer to do so. A general logic IC — a PAL in the Macintosh Plus, the BBU in the Macintosh SE — generates that signal from values it reads out of the disk-speed buffer in RAM. By running the disk motor at slower speeds the computer can store more sectors in the tracks nearer the edge of the disk.[1]
By contrast, the 800K drive controls its own motor speed and ignores the speed-control signal.[1]
Two consequences follow directly:
- On the Macintosh SE the speed-control signal is available only for the 400K external drive, not for internal drives.[1]
- The Macintosh II has no external floppy connector and no disk-speed control line at all, so it cannot use this drive.[1]
Apple adds a developer warning that is worth repeating because copy-protection schemes of the era ignored it: because some drives ignore the speed-control signal, applications should never depend on it.[1]
Compatibility
[edit | edit source]| Model | Internal drives | External drives |
|---|---|---|
| Macintosh Plus | 1 | 1 |
| Macintosh SE (before the FDHD change) | 1 or 2 | 1 |
| Macintosh II | 1 or 2 | 0 |
On the Macintosh Plus and the SE the external connector will take an 800K drive, a single-sided 400K drive, or an Apple Hard Disk 20.[1]
Why it stops working on later machines
[edit | edit source]The reason is stated plainly in Apple's own documentation: "The SWIM does not support the single-sided floppy disk drive."[1]
The SWIM is the controller in the Macintosh SE FDHD and everything after it. So a 400K drive on an SE FDHD, SE/30, IIx, IIcx, IIci, IIfx or Portable will not work, and this is a designed-in limitation rather than a fault. Apple dates the SE change to September 1989 in one place and describes machines made after August 1989 as having the FDHD drive in another; FDHD machines are identified by the letters FDHD on the front.[1]
Connector
[edit | edit source]The external connector is a DB-19 — Apple's own designation.[1]
| Pin | Signal | Pin | Signal |
|---|---|---|---|
| 1–4 | GND | 12 | PH1 (state-control line) |
| 5 | −12 V | 13 | PH2 (state-control line) |
| 6 | +5 V | 14 | PH3 (Register Write Strobe) |
| 7–8 | +12 V | 15 | /WRREQ (Write Data Request) |
| 9 | n.c. | 16 | SEL (state-control line) |
| 10 | PWM (motor-speed control) | 17 | /ENBL.EXT (External Drive Enable) |
| 11 | PH0 (state-control line) | 18 | RD (Read Data) |
| 19 | WR (Write Data) |
Pin 10, PWM, is the line this drive depends on and the 800K drive ignores.[1]
Current draw
[edit | edit source]Apple gives real numbers, which makes a power-related fault diagnosable:[1]
- A Macintosh single-sided floppy disk drive requires 500 mA at +12 V and 500 mA at +5 V.
- An Apple 800K drive requires 600 mA at +12 V and 360 mA at +5 V.
- The combined load of all devices connected to a Macintosh Plus must not exceed 600 mA at +12 V, 700 mA at +5 V and 10 mA at −12 V.
Note what that means: a 400K external drive on a Macintosh Plus is already drawing 500 of the 600 mA available at +12 V. There is no headroom for anything else on that port.
Data rate
[edit | edit source]The IWM can send data to the drive at a maximum of approximately 500 kbit/s. Because four bytes of GCR-encoded data correspond to three bytes in system RAM, the effective maximum is approximately 375 kbit/s. Actual throughput depends on seek time, RAM access and other system tasks.[1]
Daisy-chaining
[edit | edit source]An Apple Hard Disk 20 plugs into the computer and the external floppy drive plugs into the DB-19 on the back of the Hard Disk 20; the pinout of that connector is identical to the computer's.[1]
Disassembly
[edit | edit source]Apple's procedure:[2]
- Turn the drive over, bottom facing up. Remove the six screws from the bottom cover.
- Lift the back of the cover about an inch and pull it out from the front bezel.
- Lift the back of the metal drive housing — supporting the cable connector as you do — and remove the drive from the bottom cover.
- Remove the cable connector.
- Remove the screw that holds the grounding tab in place.
- Remove the screw on the outside of the metal drive housing and slide the drive out of the housing.
The grounding tab screw is the one people miss; the drive will not slide out with it fitted.
Troubleshooting
[edit | edit source]Not recognised on a later Macintosh
[edit | edit source]Not a fault. The SWIM does not support single-sided drives.[1] Test the drive on a Macintosh Plus, an SE made before the FDHD change, or a 128K/512K.
Speed errors, or reads fail on outer tracks
[edit | edit source]Consider the host as well as the drive. This drive's motor speed is generated by the computer through the PWM line on pin 10.[1] A fault in the PAL (Macintosh Plus) or BBU (Macintosh SE) that generates it, or a break in pin 10, produces disk errors that look exactly like a worn mechanism.
Will not read at all
[edit | edit source]Clean the head with a 3.5-inch head-cleaning disk. The single head is on the bottom of the mechanism — it is a single-sided drive.[1]
Will not eject
[edit | edit source]Use the emergency eject hole before dismantling anything.
Intermittent or dead with other devices attached
[edit | edit source]Check the power budget above. A 400K drive takes 500 mA of the Macintosh Plus's 600 mA +12 V allowance on its own.[1]
What Is Not Documented
[edit | edit source]No Apple figures for this drive's release date, retail price, discontinuation date, dimensions, weight, rotation speed range or sector-per-zone layout could be traced to a source consulted here, and none are stated. In particular, the "5 zones of 16 tracks", "8–12 sectors per track" and "394–590 RPM" figures that circulate are not in Apple's own chapter, which says only that running the motor at slower speeds lets the computer store more sectors in the tracks nearer the edge of the disk.[1] The closely related Apple 3.5 Drive mechanism is specified by Apple, and those figures are on the Apple Floppy Disk Drive page.[3]
See Also
[edit | edit source]References
[edit | edit source]- ↑ 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 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 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.
- ↑ Apple 400K Drive Service Source, Apple Computer, Inc. — hosted on this wiki as File:Apple 400k drive.pdf. Take Apart, "400K Mechanism": six screws in the bottom cover; lift the back of the cover about an inch and pull it out from the front bezel; lift the back of the metal drive housing while supporting the cable connector; remove the cable connector; remove the screw holding the grounding tab; remove the screw on the outside of the metal drive housing and slide the drive out. Plus an exploded view.
- ↑ Apple 3.5 Drive Service Source, Apple Computer, Inc. — hosted on this wiki as File:Apple 3.5 drive.pdf. Specifications: disk diameter 3.5 in., 2 recording surfaces, 80 tracks per inch; seek time track-to-track 6 ms maximum, settle time 30 ms maximum, drive startup time 600 ms maximum; head position accuracy ±0.035 mm; formatted capacity 800K and unformatted 1,246K, with the note that disks should be certified double-sided media; the list of directly supported computers and the note that one additional drive can be daisy-chained on the Apple IIGS; operating temperature 40–122 °F (5–50 °C), storage ‒40 to 140 °F with no condensation, relative humidity 5–90%; electrical +12 V standby 10 µA, typical 120 mA, peak 600 mA during eject only for a 2-second maximum, and +5 V standby 10 mA, typical 360 mA; size 2.01 × 4.72 × 7.87 in. (51 × 120 × 200 mm) and weight 2.8 lb (1.3 kg). Troubleshooting symptom charts, including the yellow-versus-red logic-board-to-drive cable checks and the CXD1085A/CXD1085B daisy-chain gate-array revision.