RetroTechCollection

Macintosh II

The Macintosh II is a desktop computer made by Apple Computer from March 1987 to January 1990. It was the first Macintosh with a separate monitor, expansion slots (six NuBus slots) and colour graphics, and the first to use the Motorola 68020.[1] Apple's service manual covers it together with the Macintosh IIx and Macintosh IIfx, which use the same case design.[2]

Macintosh II
Macintosh II
Specifications
ManufacturerApple Computer, Inc.
TypeDesktop personal computer
Released2 March 1987
Discontinued15 January 1990
Intro priceUS$5,498 at introduction
CPUMotorola 68020 at 15.6772 MHz
Memory1 MB, expandable to 8 MB (eight 30-pin SIMM slots)
Storage800K floppy drive; optional second 800K drive; optional 1.4 MB upgrade; optional 40, 80 or 160 MB SCSI hard drive
DisplayNone built in; NuBus video card required
SoundApple sound chip, 8-bit stereo at 44.1 kHz, four-voice wavetable synthesis
ROM256 KB
FPU / coprocessorMotorola 68881
Ports / interfaceSCSI (DB-25), 2 × ADB, 2 × serial (mini DIN-8), stereo sound jack, 6 × NuBus
Power220 W maximum excluding monitor; 100-240 V AC automatically configured, 48-62 Hz
Dimensions14.0 cm (5.5 in) H × 47.4 cm (18.7 in) W × 36.5 cm (14.4 in) D
Weight10.9 kg (24 lb) without hard drive
OS / FirmwareSystem Software 2.0 (System 4.1) to System 7.5.5
SuccessorMacintosh IIx
CodenameMilwaukee
Model no.M5000

History

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The project was started in 1985 by hardware engineers Michael Dhuey and Brian Berkeley, without the approval of Steve Jobs, who opposed expansion slots and colour. It was first called "Little Big Mac" and then codenamed Milwaukee, after Dhuey's home town. After Jobs left Apple in September 1985 the project continued openly. The case was designed by Hartmut Esslinger.[1]

Apple introduced the Macintosh II at AppleWorld in Los Angeles on 2 March 1987, alongside the Macintosh SE, at US$5,498; small-volume shipments began two months later. In September 1988 Apple raised its price by about 20 per cent, shortly before the Macintosh IIx replaced it. The Macintosh IIcx arrived in early 1989, and Macintosh II sales ended in January 1990. Apple sold logic board upgrades that turned a Macintosh II into a IIx or IIfx.[1][3]

Specifications

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Macintosh II specifications (Apple)[2]
Item Specification
Processor Motorola 68020 at 15.6772 MHz; optional PMMU
Coprocessor Motorola 68881
Addressing 32-bit registers, 32-bit address bus, 32-bit data bus
RAM 1 MB, expandable to 8 MB
ROM 256K
Floppy drives Internal 800K; optional second internal 800K; optional 1.4 MB upgrade
Hard drive Optional internal 40, 80 or 160 MB SCSI
SCSI 5 MB/s; eight devices maximum (including the computer)
Other I/O Two ADB ports; two RS-232/RS-422 serial ports (mini DIN-8); six NuBus slots with full 32-bit address and data
Sound Apple custom sound chip: 8-bit stereo sampling at 44.1 kHz, four-voice wavetable synthesis; stereo output through the sound jack
Power 100-240 V AC, automatically configured; 48-62 Hz single phase; 220 W maximum, not including the monitor
Size and weight 5.5 × 18.7 × 14.4 in (14.0 × 47.4 × 36.5 cm); 24 lb (10.9 kg), more with a hard drive

There is no built-in video: at least one NuBus slot holds a video card.[1]

Hardware

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Macintosh II logic board

Logic board and memory

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The logic board has eight 30-pin SIMM sockets in two banks, A and B.[4] Apple's symptom charts single out Apple-labelled SIMMs made by NEC with a date code of 9052 or earlier: they cause the error chord at start-up, a failure to boot, ghosting or lost video, hangs when the first application launches, and ID errors. Apple's cure is to replace them.[2]

Logic board part numbers are 661-0528 (II), 661-0529 (IIx) and 661-0522 (IIfx). The power supply is 661-0375 for the II and IIx and 661-0542 for the IIfx.[2]

Memory management

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The Macintosh II is supplied with Apple's HMMU chip in a socket. For virtual memory or A/UX it needs a Motorola 68851 PMMU: Apple's upgrade procedure prises out the HMMU and fits the PMMU in the same socket, matching the dot on the chip to the dot on the socket.[2] The IIx and IIfx have the PMMU built into their 68030.

ROM and the 1.4 MB drive upgrade

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Macintosh II ROMs made until about November 1987 could not recognise more than 1 MB of address space on a NuBus card, and Apple recalled them.[1]

The 1.4 MB floppy drive upgrade replaces all four ROM chips with 342-0639 (HI, at C13), 342-0640 (MED HI, C12), 342-0641 (MED LO, E13) and 342-0642 (LO, E12), and replaces the IWM chip with a SWIM. The drive needs system software 6.0.2 or later; with older software the Macintosh II treats it as an 800K drive. By the time of Apple's 1995 manual the kit was no longer available, and Apple's route to a SuperDrive was a IIx or IIfx logic board.[2]

Batteries

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Two ½AA lithium cells on the logic board keep the clock and parameter RAM (B1) and supply the power-on circuit (B2).[4] Apple's instruction is to replace a cell that reads below 3.2 V on the 10 V DC range.[2] On the original Macintosh II the cells are 3 V Varta units with pigtail leads soldered to the board; later boards have 3.6 V Tadiran TL-5112 cells in snap-in holders.[4] Before fitting new cells to a board with soldered batteries, Apple fits a battery holder board: cut the old leads, desolder the four connections with an iron of 50 W or less without forcing them, and solder in the holder with its positive side in the holes marked positive.[2]

If the computer will not start from either the keyboard or the rear power switch, the usual cause is a flat B2. Pina reads good cells at 3.2-3.85 V, weak at 2.3-3.1 V and dead below 2.3 V, and says to change both cells together.[4] A leaking cell damages the logic board. Lithium residue is neutralised with bicarbonate of soda, not vinegar; see Battery Explosion, Capacitor or Corrosion Damage.

Power supply

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Apple rates the supply at 220 W maximum, excluding the monitor, with automatic 100-240 V input.[2] Pina gives the part as 699-0389, made by Astec or Sony and rated 156 W peak, and lists the voltages he measured on its connector:[4]

Power supply connector (Pina, Table 4-3)
Pin Signal Measured range
1 +12 V 11.50-12.80 V
2-6 +5 V 4.90-5.20 V
7-12 Ground -
13 No connection -
14 −12 V −13.40 to −10.80 V
15 /PFW (power fail warning) -

Apple publishes no rail tolerances and no voltage adjustment for the Macintosh II. The supply is started by the logic board: for bench testing, Pina powers it with mains connected and a 3 V source from two AA cells touched to pin 15, the same method he uses to start a machine with a dead B2.[4] Apple's symptom chart notes that the thermal protection circuit can shut the system down if the vents on the sides and top are blocked, and that it recovers after 30-40 minutes.[2]

Fuses

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Pina identifies two 1 A subminiature fast-acting fuses on the original Macintosh II logic board. F1, next to the internal hard drive connectors, is the likely fault when no external SCSI device is recognised; F2, behind the ADB connectors, when no ADB device works. A good fuse reads close to 0 Ω.[4]

Troubleshooting

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Apple's symptom charts for the II, IIx and IIfx cover the error chord, power, video, floppy drives, hard drives and peripherals.[2] Selected entries:

From Apple's symptom charts
Symptom Apple's cures, in order
Error chord at start-up SIMM verification; replace NEC SIMMs dated 9052 or earlier; logic board
No power: black screen, fan off, LED off Cables; monitor on its own wall socket; power cord; check batteries; power supply; logic board
Clicking, chirping or thumping Remove extra NuBus cards; power supply; logic board
Shuts down intermittently Clear the vents and wait 30-40 minutes; power cord; batteries; power supply; logic board
Black screen, fan and LED on, drives working Monitor brightness; try the monitor on another Mac; video cable; move the video card to another slot; video card; SIMMs; logic board; power supply
Internal hard drive dead, LED off, no spin Remove the data cable; power cable; check +5 V and +12 V at the drive; drive; logic board
Works with internal or external SCSI device, not both External device must not be ID 0 (internal drive) or 7 (computer); check termination; terminator; the external device
Will not eject a disk Hold the mouse button down while switching on; drive

The meaning of the start-up tones and Sad Mac codes is on Sad Mac Error Codes.

Documentation

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  •  
    Motorola 68020
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    Motorola 68881 FPU
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References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 Macintosh II, Wikipedia—link(accessed 2026-09-30) History, designers, codenames, launch at AppleWorld 1987, price, 1988 price rise, ROM NuBus recall; the article cites Steven Levy, "The Making of the Macintosh II", Macworld, May 1987, pp. 55-63, and InfoWorld, 26 October 1987, p. 47.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 Apple Computer, Macintosh II/IIx/IIfx Service Source (1995), File:Macintosh ii.iix.iifx.pdf; see Macintosh II/IIx/IIfx Service Source. Page numbers are the PDF's: Specifications pp. 5-12; Symptom Charts pp. 15-31; Take Apart pp. 33-52; Upgrades pp. 54-67; Battery Verification, Replacement and Holder Board pp. 69-79; Exploded View p. 87.
  3. ↑ Apple Macintosh II (Original) Specs, EveryMac—link(accessed 2026-09-30) Introduced 2 March 1987, discontinued 15 January 1990; model M5000, Gestalt ID 6; two 3.6 V lithium batteries soldered to the board; supported system software 2.0 to 7.5.5.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 Larry Pina, Macintosh II Repair and Upgrade Secrets (Brady Publishing, 1991, ISBN 0-13-929530-5), hosted as Macintosh II Repair and Upgrade Secrets. Chapter 4, pp. 102-109 (power-on problems, B1/B2, jump-starting, power supply 699-0389 and Table 4-3, real-time clock, fuses F1 and F2); chapter 6, p. 158 (banks A and B). A secondary source.


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