Macintosh IIx

The Macintosh IIx was introduced on September 19, 1988, as an incremental upgrade to the Macintosh II. The IIx replaced the 16 MHz Motorola 68020 processor with a 68030 running at the same clock speed, added the 68882 FPU as standard, and introduced the 1.44 MB SuperDrive (FDHD) floppy drive. The IIx maintained the same six-slot NuBus architecture and modular case design as its predecessor while adding integrated PMMU support and 256 bytes each of instruction and data cache.

Macintosh IIx

Macintosh IIx
Specifications
Manufacturer	Apple Computer, Inc.
Type	Personal computer
Released	September 19, 1988
Discontinued	October 15, 1990
Intro price	US$7,769 – $9,369 (with 40 MB HD)
CPU	Motorola 68030 @ 16 MHz
Memory	1 MB or 4 MB standard, expandable to 128 MB
Storage	Optional 40 MB or 80 MB SCSI hard drive
Display	None built-in (requires NuBus graphics card)
Sound	8-bit stereo, 22.254 kHz sampling
Dimensions	5.5" H × 18.5" W × 14.4" D (140 × 470 × 365 mm)
Weight	24 lbs (10.9 kg)
OS / Firmware	System 6.0.2 – Mac OS 8.1 (with Mode32)
Predecessor	Macintosh II
Successor	Macintosh IIfx
Codename	Spock, Stratos
Model no.	M5810 (1 MB), M5820 (4 MB)

Development & Market Position

Apple developed the IIx under the codenames "Spock" and "Stratos" as a straightforward evolution of the Macintosh II architecture. The "x" suffix indicated the presence of the 68030 CPU, a naming convention Apple used across multiple models including the Macintosh IIcx and Macintosh IIvx.

Released at $7,769 for a base configuration or $9,369 with a 40 MB hard drive, the IIx targeted professional users requiring expandability and performance. The machine competed directly with workstations from Sun Microsystems, Silicon Graphics, and Hewlett-Packard. Apple increased the Macintosh II's price by approximately 20% just before the IIx introduction, positioning the new model as a modest upgrade cost.

Model Configurations

The IIx was available in several standard configurations:

Base Models

• Macintosh IIx 1/0 – 1 MB RAM, dual 1.44 MB floppy drives, no hard drive
• Macintosh IIx 4/0 – 4 MB RAM, dual 1.44 MB floppy drives, no hard drive
• Macintosh IIx 1/40 – 1 MB RAM, one 1.44 MB floppy, 40 MB hard drive
• Macintosh IIx 4/40 – 4 MB RAM, one 1.44 MB floppy, 40 MB hard drive
• Macintosh IIx 4/80 – 4 MB RAM, one 1.44 MB floppy, 80 MB hard drive

All configurations required at least one NuBus graphics card for video output, as the IIx had no built-in video capability.

General Maintenance

Power-on circuit repair, battery replacement, capacitor inspection, and cleaning procedures are documented in Macintosh IIx General Maintenance.

PCB Architecture & Service Documentation

The IIx consists of a large logic board with integrated I/O and expansion, plus a separate power supply unit:

Logic Board

The IIx logic board features:

• Motorola 68030 processor at 16 MHz with integrated MMU
• Motorola 68882 FPU at 16 MHz
• ROM SIMM slot containing required 256 KB ROM
• Eight 30-pin SIMM slots in two banks of four
• Six NuBus slots for expansion cards
• SWIM chip for SuperDrive support

Power Supply

The power supply provides:

• +5V, +12V, -12V regulated outputs
• 230W maximum output
• Soft power control via ADB
• Pass-through AC outlet

Apple Service Manual

Service documentation is available on the Apple Service Source page.

Capacitor Replacement Guide

Surface-mount electrolytic capacitors on the IIx logic board are prone to leakage after 30+ years. Replacement procedures and specifications are documented on the Macintosh IIx Capacitor Replacement Guide page.

Troubleshooting

Power-on failures, chimes of death, NuBus issues, and memory problems are covered in the Macintosh IIx Troubleshooting guide.

Technical Details

System Architecture

Sub-system	Specification (Macintosh IIx, September 1988)
CPU	Motorola 68030 @ 16 MHz • Integrated PMMU • 256 bytes I-cache + 256 bytes D-cache
Bus width	32-bit data • 32-bit address (4 GB theoretical, 128 MB actual limit)
ROM	256 KB ROM SIMM • "Dirty" ROMs require Mode32 for >8 MB RAM
RAM	1-128 MB via 30-pin SIMMs • Two banks of four slots • 120ns or faster
Video	None built-in • Requires NuBus graphics card
Sound	Apple Sound Chip (ASC) • 4-voice stereo • 22.254 kHz sampling
Storage	1.44 MB SuperDrive standard • Optional 40/80 MB SCSI hard drive
I/O Ports	ADB × 2 • Mini-DIN-8 serial × 2 • DB-25 SCSI • DB-19 floppy
Expansion	Six NuBus slots • 10 MHz bus speed • 10-40 MB/s bandwidth

Memory Configuration

The IIx uses eight 30-pin SIMM slots arranged in two banks of four. Both banks must be populated with identical SIMMs within each bank.

Memory Configurations

Bank A	Bank B	Total RAM	Notes
4 × 256 KB	Empty	1 MB	Minimum configuration
4 × 256 KB	4 × 256 KB	2 MB
4 × 1 MB	Empty	4 MB
4 × 1 MB	4 × 1 MB	8 MB	Maximum without Mode32
4 × 4 MB PAL	Empty	16 MB	Requires Mode32
4 × 4 MB PAL	4 × 1 MB	20 MB	Requires Mode32
4 × 4 MB PAL	4 × 4 MB PAL	32 MB	Requires Mode32
4 × 16 MB PAL	4 × 16 MB PAL	128 MB	Maximum, requires Mode32

Important notes:

• 4 MB and 16 MB SIMMs must be PAL (Presence Detect) type
• Mode32 or 32-bit System Enabler required for >8 MB configurations
• Bank A must be populated before Bank B can be used

ROM Specifications

The IIx requires a ROM SIMM in the dedicated ROM slot. The ROM is "32-bit dirty," containing 24-bit addressing code that limits RAM access to 8 MB without software patches.

ROM Details

Version	Size	Features	Limitations
IIx ROM	256 KB	SWIM support, 68030 optimizations	32-bit dirty, 8 MB limit without Mode32
IIfx ROM	512 KB	32-bit clean alternative	Not officially supported but functional

NuBus Architecture

The six NuBus slots provide the primary expansion capability:

NuBus Specifications

Parameter	Specification
Bus speed	10 MHz
Data width	32-bit
Address space	256 MB per slot
Bandwidth	10-40 MB/s (theoretical)
Slot numbering	9, A, B, C, D, E (hexadecimal)
Power per slot	+5V @ 2A, +12V @ 0.3A, -12V @ 0.3A

Common NuBus cards:

• Graphics cards – Apple 8•24, Radius DirectColor/GX
• Accelerators – DayStar Digital PowerCache, Radius Rocket
• Network cards – Ethernet, Token Ring adapters
• Video capture – Media Time, VideoSpigot
• Additional I/O – Serial/parallel expansion cards

SuperDrive (FDHD) System

The IIx was the first Macintosh II series computer with built-in SuperDrive support:

Technical Specifications

• Controller: SWIM (Super Wozniak Integrated Machine) chip
• Capacity: 1.44 MB (high density), 800 KB (double density), 400 KB (single density)
• Encoding: MFM for 1.44 MB, GCR for 400/800 KB
• Compatibility: Mac, ProDOS, MS-DOS formats (with software)
• Transfer rate: Up to 62.5 KB/s

Drive Support Matrix

Drive Type	Internal Support	External Support
400 KB	Read only	Read only
800 KB	Full support	Full support
1.44 MB	Full support	Full support
MS-DOS 720 KB	With Apple File Exchange	With Apple File Exchange
MS-DOS 1.44 MB	With Apple File Exchange	With Apple File Exchange

SCSI Subsystem

The IIx uses the NCR 5380 SCSI controller providing:

• SCSI-1 interface (5 MB/s maximum)
• Seven device support (ID 0-6, Mac is ID 7)
• DB-25 external connector
• 50-pin internal connector
• Asynchronous transfers only

Real-world SCSI performance typically achieves 1.4 MB/s with appropriate drives and proper termination.

Audio System

The Apple Sound Chip (ASC) provides enhanced audio capabilities:

• Four-voice wavetable synthesis
• Stereo output via dual 8-bit DACs
• 22.254 kHz standard sampling rate
• 11.127 kHz and 7.418 kHz alternate rates
• 512-byte FIFO buffer per channel

Power Specifications

• Input: 100-132V or 198-264V AC, 47-63 Hz (switch selectable)
• Maximum power: 230W
• BTU/hr: 786.6
• Power distribution:
  • +5V @ 14.0A
  • +12V @ 1.8A
  • -12V @ 0.25A
  • -5V @ 0.1A

Power-On Circuit

The IIx features a complex power-on circuit that requires functioning batteries:

Power-On Circuit Components

Component	Function	Common Failure Mode
Dual 3.6V batteries	Provide 7V for power-on circuit	Dead batteries prevent power-on
UB1, UB2 transistors	Switch power supply control	Capacitor leakage damages transistors
C5, C6 capacitors	Filter power-on circuit	Leakage breaks nearby traces
R3, R18 resistors	Current limiting	Corrosion from capacitor leakage

Without functioning batteries or with damaged power-on components, the IIx cannot start via the rear power button or ADB power key.

32-bit Addressing & Mode32

The IIx ships with "32-bit dirty" ROMs containing residual 24-bit code. This limits usable RAM to 8 MB regardless of physical installation. To access more than 8 MB:

Software Solutions

• Mode32 1.2 – For System 7.0/7.1
• Mode32 7.5 – For System 7.5.x
• 32-bit System Enabler – Apple's solution (less stable than Mode32)
• System 7.6 – Requires 32-bit clean ROMs (not compatible)

Installation Process

1. Install physical RAM beyond 8 MB
2. Install Mode32 in System Folder
3. Open Memory control panel
4. Check "32-bit Addressing"
5. Restart

Known Issues & Solutions

Power-On Failures

• No response to power button – Dead batteries or damaged power-on circuit
• Powers on via ADB only – UB1/UB2 transistor failure
• Clicking/ticking sound – Power supply protection, check for shorts

Memory Issues

• Only recognizes 8 MB – Install Mode32 and enable 32-bit addressing
• Chimes of death – Reseat SIMMs, verify matched sets
• Random crashes – Replace PAL SIMMs with correct type

Video Problems

• No video output – Verify NuBus card seated properly
• Grayscale only – Check monitor sense pins on video cable
• Distorted display – Clean NuBus contacts with contact cleaner

SCSI Issues

• Devices not recognized – Check termination and cable quality
• Slow performance – Verify proper termination at chain ends
• System hangs at startup – Remove all SCSI devices, test individually

Upgrade Paths

Processor Upgrades

• DayStar Digital PowerCache – 33/40/50 MHz 68030 accelerators
• Radius Rocket – 68040-based NuBus coprocessor cards

Video Upgrades

• Apple 8•24 GC – Accelerated 24-bit graphics
• Radius DirectColor/GX – High-performance graphics
• SuperMac Thunder/24 – 24-bit accelerated video

Storage Upgrades

• Larger SCSI drives – Up to 2 GB supported natively
• SCSI-2 cards – DayStar Digital SCSI PowerCard for faster transfers

Historical Context

The IIx served as Apple's high-end workstation from September 1988 until the Macintosh IIfx introduction in March 1990. Notable uses included:

• Industrial Light & Magic for "The Abyss" image processing
• Publishing industry for early desktop publishing
• Scientific computing with FPU-intensive applications
• CAD/CAM workstation applications

Production ceased October 15, 1990, after approximately 80,000 units sold. Support and spare parts were discontinued August 31, 1998.

Maintenance Resources

• Macintosh IIx General Maintenance – Cleaning and battery service
• Macintosh IIx Capacitor Replacement Guide – Capacitor specifications
• Macintosh IIx Troubleshooting – Diagnostic procedures
• NuBus Card Guide – Expansion card information
• SCSI Configuration Guide – Termination and setup

Related Pages

• Macintosh II – Direct predecessor
• Macintosh IIfx – High-performance successor
• Macintosh IIcx – Compact three-slot variant
• Macintosh IIci – Built-in video successor
• Mode32 – 32-bit addressing enabler