Editing Macintosh IIcx

{{Infobox computer
| name         = Macintosh IIcx
| image        = [[File:MacintoshIIcx.jpg|250px]]
| caption      = Macintosh IIcx
| manufacturer = Apple Computer, Inc.
| type         = Desktop personal computer
| release date = March 7, 1989
| discontinued = March 11, 1991
| price        = US$5,369 (1 MB RAM) – $6,669 (4 MB RAM, 80 MB HD)
| cpu          = Motorola 68030 @ 16 MHz
| memory       = 1 MB or 4 MB RAM, expandable to 128 MB
| storage      = 40 MB or 80 MB SCSI hard drive
| display      = External monitor via NuBus video card
| sound        = Stereo 8-bit, 44.1 kHz
| dimensions   = 5.9" H × 11.9" W × 14.4" D (150 × 302 × 366 mm)
| weight       = 13.6 lbs (6.2 kg)
| os           = System 6.0.3 – Mac OS 7.6.1
| predecessor  = [[Macintosh IIx]]
| successor    = [[Macintosh IIci]]
| codename     = Aurora, Cobra, Atlantic
| model        = M5650
}}

The '''Macintosh IIcx''' was introduced on March 7, 1989, as Apple's first compact modular Mac. The IIcx delivered [[Macintosh IIx]] performance in a case 7 inches narrower and 10 pounds lighter, achieved by reducing NuBus slots from six to three and implementing a revolutionary tool-free modular design. Jean-Louis Gassée famously demonstrated the IIcx's modularity by assembling one from components on stage during its introduction. The machine pioneered the horizontal/vertical case orientation that continued through the IIci and Quadra 700.

== Development & Design Philosophy ==

The IIcx emerged from Apple's recognition that the Macintosh II and IIx, while powerful, were too large for many office environments. The design team focused on three objectives:

* '''Size reduction''' without sacrificing core performance
* '''Manufacturing efficiency''' through tool-free assembly
* '''Flexible installation''' via dual-orientation capability

The resulting design eliminated three NuBus slots and reduced the power supply from 230W to 90W while maintaining the IIx's 16 MHz 68030 performance. The tool-free assembly reduced manufacturing costs and simplified field service. John Sculley reportedly requested the vertical orientation option after running out of desk space, though the monitor placement actually increased the total footprint.

== Architecture Innovation ==

The IIcx introduced several design elements that defined Apple's modular Macs through the early 1990s:

=== Tool-Free Construction ===
* RAM SIMMs installed without tools
* NuBus cards secured by thumbscrews
* Power supply connected via simple locking mechanism
* Hard drive mounted on sliding bracket
* Single central safety screw (often omitted after servicing)

=== Dual Orientation ===
* First Mac designed for horizontal or vertical placement
* Optional stand for vertical "minitower" configuration
* Rubber feet on both bottom and side panels
* Internal components oriented to work in either position

=== Compact NuBus Implementation ===
* Three slots vs. six in Mac II/IIx
* Full 32-bit NuBus architecture retained
* Shorter cards required for some slots
* No built-in video (requires NuBus card)

== General Maintenance ==
Cleaning procedures, PRAM battery management, fan maintenance, and preventive care are documented in [[Macintosh IIcx General Maintenance]].

== Service Documentation ==

The IIcx service manual details the modular construction and field-replaceable components:

<pdf width="800" height="500">File:Macintosh_IIcx_Service_Manual.pdf</pdf>

Service documentation available on the [[:Category:Apple Service Source|Apple Service Source]] page.

== Capacitor Replacement Guide ==
Electrolytic capacitors on the logic board and power supply require periodic replacement. The IIcx uses through-hole capacitors on the logic board. Specifications and procedures are documented on the [[Macintosh IIcx Capacitor Replacement Guide]] page.

== Troubleshooting ==
Boot failures related to PRAM battery, "dirty ROM" issues, memory configuration problems, and NuBus conflicts are covered in the [[Macintosh IIcx Troubleshooting]] guide.

== Technical Details ==
<templatestyles src="Template:StyledTable/styles.css" />

=== System Architecture ===
{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Sub-system !! Specification (Macintosh IIcx, March 1989)
|-
| '''CPU''' || Motorola 68030 @ 16 MHz • Integrated PMMU
|-
| '''FPU''' || Motorola 68882 @ 16 MHz • 80-bit precision
|-
| '''Bus speed''' || 16 MHz (1:1 with CPU)
|-
| '''L1 Cache''' || 256 bytes instruction • 256 bytes data (on-chip)
|-
| '''L2 Cache''' || None (upgrade slot available)
|-
| '''ROM''' || 256 KB (512 Kbit × 4 chips) • "Dirty" 24-bit code
|-
| '''RAM''' || 1-128 MB via 30-pin SIMMs • 8 slots in 2 banks
|-
| '''Video''' || None built-in • Requires NuBus card
|-
| '''Sound''' || Stereo 8-bit • 44.1 kHz sampling • 4-voice synthesis
|-
| '''Storage''' || 40 or 80 MB SCSI • 1.44 MB SuperDrive
|-
| '''I/O Ports''' || ADB × 2 • Mini-DIN-8 serial × 2 • DB-25 SCSI • DB-19 floppy
|-
| '''Expansion''' || 3 NuBus slots • Optional cache card slot
|}

=== Memory Configuration ===

The IIcx uses eight 30-pin SIMM slots arranged in two banks of four:

{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''Memory Installation Requirements'''
! Configuration !! Bank A (4 slots) !! Bank B (4 slots) !! Total RAM
|-
| Factory 1 MB || 4 × 256 KB || Empty || 1 MB
|-
| Factory 4 MB || 4 × 1 MB || Empty || 4 MB
|-
| 2 MB || 4 × 256 KB || 4 × 256 KB || 2 MB
|-
| 5 MB || 4 × 1 MB || 4 × 256 KB || 5 MB
|-
| 8 MB || 4 × 1 MB || 4 × 1 MB || 8 MB
|-
| 32 MB || 4 × 4 MB || 4 × 4 MB || 32 MB
|-
| 128 MB || 4 × 16 MB || 4 × 16 MB || 128 MB
|}

'''SIMM Specifications:'''
* 30-pin, 120ns or faster
* Supported sizes: 256 KB, 1 MB, 4 MB, 16 MB
* Must install in sets of four matching SIMMs per bank
* Bank A populated first, Bank B optional

'''32-bit Addressing Requirements:'''
* System 6 and earlier: Limited to 8 MB (24-bit addressing)
* System 7.x: Requires Mode32 utility for >8 MB access
* "Dirty ROMs" contain 24-bit code requiring Mode32
* 32-bit addressing selected in Memory control panel

=== ROM Issues ("Dirty ROMs") ===

The IIcx inherited the Mac II/IIx ROM code containing 24-bit addressing dependencies:

'''ROM Limitations:'''
* Not "32-bit clean" despite 68030's capabilities
* Contains hardcoded 24-bit addresses
* Prevents native 32-bit operation
* Limits System 6 to 8 MB RAM maximum

'''Mode32 Solution:'''
* Free utility from Connectix (later Apple)
* Patches ROM code for 32-bit cleanliness
* Required for accessing >8 MB RAM
* Version 7.5 compatible with System 7.5
* Apple's 32-bit Enabler incompatible with System 7.5

=== NuBus Architecture ===

The IIcx implements Apple's full NuBus specification across three slots:

{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''NuBus Slot Configuration'''
! Slot !! Physical Position !! Card Length !! Notes
|-
| Slot 9 (SE) || Leftmost || 12" maximum || Full access
|-
| Slot A (SD) || Center || 7" maximum || Limited by drive bay
|-
| Slot B (SC) || Rightmost || 12" maximum || Often used for video
|}

'''NuBus Specifications:'''
* 32-bit multiplexed address/data bus
* 10 MHz operation (37.5 MB/s theoretical)
* Self-configuring (no DIP switches)
* Fair arbitration between cards
* Geographical addressing
* 96-pin Euro-DIN connector

'''Common NuBus Cards:'''
* Apple 8•24 Video Card (required for display)
* Radius Precision Color series
* RasterOps ColorBoard series
* Ethernet adapters (EtherTalk)
* Accelerator cards (Radius Rocket, DayStar)

=== Custom ICs ===

{| class="wikitable styled-table" style="width:85%; text-align:center;"
! Chip !! Function !! Details
|-
| '''GLUE''' || Address decode/control || Apple custom IC for system glue logic
|-
| '''NuChip30''' || NuBus controller || Manages NuBus interface and arbitration
|-
| '''ASC''' || Apple Sound Chip || 8-bit stereo, 4-voice synthesis
|-
| '''SWIM''' || Floppy controller || SuperDrive support, replaces IWM
|-
| '''RTC''' || Real-time clock || Battery-backed timekeeping
|-
| '''VIA1''' || Versatile Interface Adapter || System control, timers
|-
| '''VIA2''' || Second VIA || Additional I/O control
|}

=== Power System ===

The IIcx uses a compact 90W power supply, significantly smaller than the II/IIx's 230W unit:

'''Power Supply Specifications:'''
* Input: 100-240V AC, 50-60 Hz
* Output: 90W maximum
* +5V @ 9.0A
* +12V @ 1.8A
* -12V @ 0.25A
* -5V @ 0.1A

'''Power Management Features:'''
* Auto-restart after power failure (new capability)
* Soft power control via ADB
* Lower heat generation than II/IIx
* Quieter fan due to reduced thermal load

=== Storage Subsystem ===

==== SCSI Implementation ====
* NCR 5380 controller
* DB-25 external connector
* 50-pin internal connector
* SCSI-1 asynchronous (5 MB/s maximum)
* Supports up to 7 devices
* Requires proper termination

==== SuperDrive (FDHD) ====
* 1.44 MB capacity (first standard on Mac II series)
* 800 KB and 400 KB compatibility
* SWIM controller
* DB-19 external floppy port (new feature)
* Auto-inject mechanism

==== Hard Drive Options ====
* 40 MB Quantum ProDrive LPS
* 80 MB Quantum ProDrive or Conner
* 3.5" half-height form factor
* 5400 RPM typical
* 28ms average access time

=== Audio System ===

The IIcx features enhanced stereo capabilities:

'''Audio Specifications:'''
* 8-bit stereo sampling at 44.1 kHz
* Four-voice wavetable synthesis
* Apple Sound Chip (ASC)
* Stereo mini-jack output
* Drives 32-ohm headphones or line-level

'''Sound Generation:'''
* Sample playback from RAM
* Real-time synthesis capability
* Compatible with MacRecorder for input
* Sound Manager 2.0 support

=== Case Constraints ===

The compact design imposed several limitations:

'''Storage Limitations:'''
* Cannot accommodate full-height drives
* No space for 5.25" drives
* Single 3.5" half-height bay only
* Some third-party drives incompatible

'''Expansion Constraints:'''
* Three NuBus slots vs. six in II/IIx
* Center slot limited to 7" cards
* No processor direct slot (PDS)
* No cache card slot on early boards

'''Thermal Considerations:'''
* Smaller fan than II/IIx
* Adequate for standard configuration
* Multiple high-power cards may cause overheating
* Vertical orientation improves convection

== Known Issues & Solutions ==

=== Critical Issues ===
* '''No boot without PRAM battery''' – IIcx will not start with dead/missing battery
* '''Dirty ROMs''' – Require Mode32 for >8 MB RAM access
* '''Soldered CPU''' – Most IIcx boards have non-upgradeable 68030
* '''No built-in video''' – Requires NuBus video card purchase

=== Common Problems ===
* Electrolytic capacitor leakage on logic board
* Power supply capacitor failure
* PRAM battery corrosion damage
* NuBus slot contact oxidation
* Fan bearing failure causing noise

=== Upgrade Limitations ===
* CPU soldered to logic board (unlike II/IIx)
* No Level 2 cache support on many boards
* Maximum 16 MB SIMMs (128 MB ceiling)
* Three NuBus slots may be insufficient

== Upgrade Options ==

=== Processor Upgrades ===
NuBus accelerator cards:
* DayStar Universal PowerCache (33, 40, 50 MHz 68030)
* Applied Engineering TransWarp (25, 33 MHz 68040)
* Radius Rocket (25, 33 MHz 68040)
* TechWorks NuBus accelerator (33 MHz 68040)

=== Logic Board Swap ===
* '''Macintosh IIci board''' – Direct replacement, adds built-in video, 25 MHz CPU
* Requires case modification for IIci's additional ports
* IIci boards available inexpensively on used market
* 80ns or faster RAM transfers directly

=== Memory Upgrade Strategy ===
1. Maximum System 6 configuration: 8 MB (8 × 1 MB SIMMs)
2. System 7 with Mode32: Start with 20 MB (4 × 4 MB + 4 × 1 MB)
3. Maximum configuration: 128 MB (8 × 16 MB SIMMs)

== Historical Context ==

The IIcx represented several important transitions:

* First truly compact modular Mac (predating "pizza box" form factor)
* Introduced tool-free assembly to Mac line
* Pioneered dual-orientation case design
* Last Mac II series with "dirty" ROMs

Production numbers indicate approximately 200,000 units sold during its two-year run. The IIcx found particular success in space-constrained offices and as a lower-cost alternative to the six-slot II/IIx. The modular design philosophy influenced all subsequent professional Macs through the mid-1990s.

== Design Legacy ==

The IIcx's innovations influenced Apple's design philosophy:

* Tool-free assembly became standard for pro models
* Compact three-slot design continued in IIci
* Vertical orientation evolved into Quadra 700/900
* Modular construction simplified manufacturing
* Case design reused for IIci (Apple's most popular Mac II)

The IIcx demonstrated that professional power could be delivered in a compact package, setting the template for the successful IIci and later establishing the design language for the Quadra series.

== Maintenance Resources ==
* [[Macintosh IIcx General Maintenance]] – Cleaning and preventive care
* [[Macintosh IIcx Capacitor Replacement Guide]] – Complete specifications
* [[Macintosh IIcx Troubleshooting]] – Diagnostic procedures
* [[Mode32]] – Enabling 32-bit addressing
* [[NuBus]] – Expansion card information

== Related Pages ==
* [[Macintosh II]] – Original modular Mac
* [[Macintosh IIx]] – Direct predecessor
* [[Macintosh IIci]] – Direct successor with built-in video
* [[Macintosh IIfx]] – High-end contemporary
* [[Quadra 700]] – Spiritual successor using same case

[[Category:Apple Vintage Computers]]
{{Navbox-AppleVintage}}