Editing Macintosh IIcx (section)

== 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