Macintosh IIfx
 | |
| Macintosh IIfx | |
| Specifications | |
|---|---|
| Manufacturer | Apple Computer, Inc. |
| Type | Desktop personal computer |
| Released | March 19, 1990 |
| Discontinued | April 15, 1992 |
| Intro price | US$8,969 – $12,000 |
| CPU | Motorola 68030 @ 40 MHz |
| Memory | 4 MB RAM, expandable to 128 MB |
| Storage | 40 MB, 80 MB, or 160 MB SCSI hard drive |
| Display | No built-in video (requires NuBus card) |
| Sound | Stereo 8-bit, 22.254 kHz |
| Dimensions | 5.8" H × 18.7" W × 14.4" D (147 × 474 × 365 mm) |
| Weight | 24 lbs (10.9 kg) |
| OS / Firmware | System 6.0.5 – Mac OS 7.5.5 |
| Predecessor | Macintosh IIx |
| Successor | Macintosh Quadra 900 |
| Codename | F-16, F-19, Stealth, Blackbird, Zone 5, Four Square, Weed Whacker |
| Model no. | M5780 |
The Macintosh IIfx was introduced on March 19, 1990, as Apple's flagship professional workstation. Dubbed "Wicked Fast" by its Product Manager, Frank Casanova – who came to Apple from Apollo Computer in Boston, Massachusetts, where the Boston term "wicked" is commonly used to denote anything extreme – the IIfx runs at a clock rate of 40 megahertz, has 32 KB of Level 2 cache, six NuBus slots, and includes a number of proprietary ASICs and coprocessors. At $8,969 to $12,000, the IIfx commanded premium pricing for its unprecedented performance, earning the derisive nickname "F##king eXpensive" among cost-conscious buyers. The IIfx remained the fastest 68030-based Macintosh until succeeded by the Quadra 900 in October 1991.
Engineering Philosophy
[edit | edit source]The IIfx represented a radical departure from incremental Mac II improvements. While the IIcx and IIci focused on integration and cost reduction, the IIfx pursued absolute performance regardless of price. Apple engineers implemented multiple architectural innovations:
- Apple didn't go that route – the IIfx ran a 40 MHz 68030 CPU and 40 MHz 68882 FPU (math chip) on a 40 MHz system bus. It used a special 64-bit memory module that could overlap read and write operations for improved speed. It had a 32 KB L2 cache on the motherboard, since even its high speed memory couldn't keep up at 40 MHz.
- Dual I/O processors (IOPs) handled peripheral operations independently
- Proprietary high-speed RAM architecture with dedicated data paths
- Hardware DMA controller for SCSI operations
- Six NuBus slots maintained maximum expandability
This approach produced the fastest Mac of its generation but required specialized components and software optimization, limiting broad compatibility.
Architecture Revolution
[edit | edit source]I/O Processor System
[edit | edit source]The IIfx introduced dedicated I/O processors, a first for Macintosh:
The IIfx includes two special dedicated processors for floppy disk operations, sound, ADB, and serial communications. These I/O chips feature a pair of 10 MHz embedded 6502 CPUs, which is the same CPU family used in Apple II machines. These IOPs freed the main CPU from routine tasks:
- IOP A: Managed floppy disk controller (SWIM chip) and ADB ports
- IOP B: Handled serial communications (SCC chip)
Each IOP contained:
- 6502 core running at 10 MHz (vs 1 MHz in Apple II)
- 32 bytes of local RAM
- Direct hardware interface circuitry
On the Macintosh IIfx, the CPU no longer handles I/O operations like floppy disk access, SCC access, and mouse events. Instead of the CPU doing all of the work, the IIfx contains a couple of separate I/O processors, Apple custom ASICs, to handle all floppy disk, mouse, and SCC I/O.
Memory Architecture
[edit | edit source]The IIfx employed unique 64-pin SIMMs with dual-ported architecture:
The IIfx introduced latched read/write RAM to the Apple lexicon. Using a 64-pin SIMM different from that in any other Macintosh, the IIfx could overlap read and write operations. This design enabled:
- Separate 8-bit input and output data buses
- Overlapping read/write operations
- 80ns access time requirement
- Parity support option (rare for 68K Macs)
General Maintenance
[edit | edit source]Cleaning procedures, PRAM battery management, power supply service, and preventive care are documented in Macintosh IIfx General Maintenance.
Service Documentation
[edit | edit source]The IIfx service manual details the complex architecture and modular construction:
Service documentation available on the Apple Service Source page.
Capacitor Replacement Guide
[edit | edit source]The IIfx logic board shipped with either tantalum or electrolytic surface-mount capacitors. Electrolytic versions require replacement. Specifications and procedures are documented on the Macintosh IIfx Capacitor Replacement Guide page.
Troubleshooting
[edit | edit source]Boot failures, SCSI termination issues, IOP problems, and diagnostic procedures are covered in the Macintosh IIfx Troubleshooting guide.
Technical Details
[edit | edit source]System Architecture
[edit | edit source]| Sub-system | Specification (Macintosh IIfx, March 1990) |
|---|---|
| CPU | Motorola 68030 @ 40 MHz • Integrated PMMU |
| FPU | Motorola 68882 @ 40 MHz • 80-bit precision |
| Bus speed | 40 MHz (1:1 with CPU) • Fastest Mac II bus |
| L1 Cache | 256 bytes instruction • 256 bytes data (on-chip) |
| L2 Cache | 32 KB SRAM on motherboard • Direct-mapped |
| ROM | 512 KB • 32-bit clean • On ROM SIMM |
| RAM | 4-128 MB via 64-pin SIMMs • Dual-ported architecture |
| I/O Processors | Two 6502-based IOPs @ 10 MHz |
| Video | None built-in • Requires NuBus card |
| Sound | Stereo 8-bit • 22.254 kHz • ASC chip |
| Storage | 40/80/160 MB SCSI • 1.44 MB SuperDrive |
| I/O Ports | ADB × 2 • Serial × 2 • SCSI • Floppy |
| Expansion | 6 NuBus slots • 1 PDS (030 Direct Slot) |
Memory Configuration
[edit | edit source]The IIfx uses eight 64-pin SIMM slots arranged in two banks:
| Configuration | Bank A (4 slots) | Bank B (4 slots) | Total RAM | Notes |
|---|---|---|---|---|
| Factory minimum | 4 × 1 MB | Empty | 4 MB | Standard configuration |
| 4 × 1 MB | 4 × 1 MB | 8 MB | Common upgrade | |
| 4 × 4 MB | Empty | 16 MB | Single bank populated | |
| 4 × 4 MB | 4 × 1 MB | 20 MB | Mixed configuration | |
| 4 × 4 MB | 4 × 4 MB | 32 MB | Popular configuration | |
| 4 × 8 MB | 4 × 8 MB | 64 MB | Unofficial support | |
| Maximum | 4 × 16 MB | 4 × 16 MB | 128 MB | Requires 16 MB SIMMs |
Memory Specifications:
- Type: 64-pin proprietary SIMMs
- Speed: 80ns or faster required
- Data path: 8-bit wide per SIMM (32-bit total per bank)
- Architecture: Dual-ported with separate read/write paths
- Parity: Optional 9-bit SIMMs for error checking
- Installation: Must populate in sets of four matching SIMMs
Important Notes:
- Although the IIfx uses the same type of 64-pin SIMMs as the LaserWriter IINTX, you cannot use memory from the printer in the IIfx – the printer memory is not fast enough for the Mac IIfx.
- Bank A sockets are furthest from front panel
- Bank B sockets are nearest to front panel
- Drive assembly must be removed for RAM access
Custom ASIC Architecture
[edit | edit source]The IIfx employed multiple custom chips for system control:
| Chip | Function | Details |
|---|---|---|
| OSS | Operating System Support | Address decoding, control signals |
| IOP A | I/O Processor A | 6502 @ 10 MHz, controls SWIM/ADB |
| IOP B | I/O Processor B | 6502 @ 10 MHz, controls SCC |
| ASC | Apple Sound Chip | 8-bit stereo, 4-voice synthesis |
| SWIM | Super Wozniak Integrated Machine | Floppy controller (via IOP) |
| BIU30 | Bus Interface Unit | NuBus to processor bus bridge |
| BIU2 | Bus Interface Unit 2 | Secondary bus control |
| CGTO | Clock Generation/Timeout | System timing control |
I/O Processor Details
[edit | edit source]IOP Architecture
[edit | edit source]Each IOP contained:
- CPU Core: 65C02 running at 10 MHz
- Local RAM: 32 bytes for buffering
- Interface logic: Direct hardware control
- Communication: Shared memory with main CPU
IOP A Functions
[edit | edit source]- Floppy disk operations via SWIM chip
- Apple Desktop Bus (ADB) transactions
- Mouse tracking and keyboard scanning
- Eliminates CPU polling overhead
IOP B Functions
[edit | edit source]- Serial port A and B management
- SCC chip control
- High-speed serial support (up to 920 Kbps)
- Bypass mode for compatibility
Software Interface
[edit | edit source]The I/O processing hardware is subject to change, and applications which attempt to access it directly are likely to break when new hardware is introduced. Apple provided:
- System patches for IOP communication
- Updated drivers for disk and serial access
- Compatibility mode for legacy software
Processor Direct Slot (PDS)
[edit | edit source]The IIfx PDS provided direct 68030 bus access:
PDS Specifications:
- Connector: 120-pin Euro-DIN
- Data path: Full 32-bit
- Speed: 40 MHz synchronous
- Address space: Full 4 GB range
- DMA: Supports bus mastering
Compatible Cards:
- DayStar PowerCache accelerators
- Applied Engineering TransWarp
- Radius Rocket coprocessor cards
- Custom development boards
SCSI Subsystem
[edit | edit source]The IIfx featured enhanced SCSI performance:
SCSI Controller:
- NCR 53C80 or compatible chip
- Hardware DMA support via custom logic
- the SCSI bus could burst to 4 MB/sec. – faster than any hard drive of the time.
- Asynchronous SCSI-1 protocol
Special Requirements:
- The IIfx requires a special black-colored SCSI terminator for external drives.
- Standard gray terminators cause signal issues
- Internal termination differs from other Mac II models
Performance Characteristics
[edit | edit source]Benchmark comparisons (relative to Mac IIci):
CPU Performance:
- Integer: 160% of IIci speed
- Floating-point: 160% with 68882
- Speedometer benchmarks show a stock IIfx is almost twice as powerful as a base 25 MHz Mac IIci – and about 60% faster than the IIci with a 32 KB L2 cache.
System Performance:
- Memory bandwidth: 160 MB/s peak
- Effective RAM access: 60.95 MB/s average
- Cache hit rate: >90% typical
- NuBus: Standard 10 MHz operation
I/O Performance:
- Serial ports: Up to 920 Kbps (vs 230.4 Kbps standard)
- SCSI: 4 MB/s burst, 2.5 MB/s sustained
- Floppy: Standard 62.5 KB/s
- ADB: Enhanced responsiveness via IOP
Model Configurations
[edit | edit source]When first introduced, the IIfx was offered in the following configurations: Macintosh IIfx: 4 MB memory, 1.44 MB SuperDrive. US$8,969. Macintosh IIfx 4/80: 4 MB memory, 80 MB HDD. US$9,869. Macintosh IIfx 4/160: 4 MB memory, 160 MB HDD. US$10,969.
Additional configurations:
- IIfx 4/80 with Parity: 4 MB parity RAM, 80 MB HDD
- IIfx 4/80 with A/UX: 4 MB RAM, 160 MB HDD, A/UX 2.0 preinstalled
Common upgrades included:
- Apple 8•24GC accelerated graphics card
- Additional RAM (typically to 8 or 32 MB)
- External SCSI devices with black terminator
Logic Board Layout
[edit | edit source]The IIfx logic board featured a complex multi-layer design:
Component Placement
[edit | edit source]- Front edge: Six NuBus slots, PDS connector
- Center: CPU, FPU, L2 cache, ROM SIMM slot
- Rear edge: I/O connectors, PSU connection
- RAM area: Eight 64-pin SIMM sockets behind drive bay
Capacitor Configuration
[edit | edit source]One of the rather unusual things about the IIfx logic board is that it was designed to use either electrolytic or tantalum caps, with two distinct sets of pads for each surface-mount electrolytic cap on the board.
Two board variants exist:
- Tantalum version: More reliable, rarely needs service
- Electrolytic version: Requires periodic replacement
Surface-mount capacitors (electrolytic boards):
- 10 × 47 µF 16V
- 4 × 10 µF 25V
- 2 × 220 µF 16V
- 2 × 470 µF 25V
- 1 × 1000 µF 10V
Be warned though - most boards with tantalum caps will still have two electrolytic caps in the power circuit. Any surface mount electrolytic cap in the system must be changed out, as the originals leak and will damage the board if left installed.
Known Issues & Solutions
[edit | edit source]Critical Issues
[edit | edit source]- C1 capacitor failure – capacitor C1, if a factory tantalum, is prone to exploding due to being slightly underrated for its application.
- Battery leakage – Two batteries required (PRAM and startup)
- SCSI termination – Must use black terminator for external devices
- IOP compatibility – Some software bypasses IOPs, causing failures
Common Problems
[edit | edit source]- No power-on: Dead startup battery prevents soft power
- Floppy failures: IOP issues or drive mechanical problems
- Serial errors: Software accessing SCC directly fails
- Memory errors: 64-pin SIMMs sensitive to oxidation
Upgrade Strategies
[edit | edit source]Accelerator Options
[edit | edit source]Limited due to already-fast architecture:
- Applied Engineering TransWarp (25-33 MHz 68040)
- Fusion Data TokaMac FX (33 MHz 68040)
- Radius Rocket (25-40 MHz 68040)
Modern Solutions
[edit | edit source]- This repository contains a PCB layout for a 16MB SIMM to be used in the Macintosh IIfx system. The SIMM is a proprietary, 8 bit wide proprietary type with 64 pins.
- ROM SIMM replacements for custom ROMs
- SCSI2SD with proper termination
- Recapped power supplies essential
Easter Egg
[edit | edit source]Setting the system date to March 19, 1990, configuring the monitor for 256 colors, and restarting while holding Command+Option+F+X displays a digitized color photograph of the IIfx development team.
Historical Context
[edit | edit source]The IIfx occupied a unique position as Apple's performance flagship:
Market Position
[edit | edit source]A September 10, 1990, article in Computerworld observed, "Mac IIfx: Not yet to be feared." It described how, months after the computer's release, the IIfx still struggled to become a serious contender in the workplace. Despite mixed commercial reception:
- Dominated high-end DTP and 3D rendering
- Industrial Light & Magic upgraded their image processing hardware to the IIfx by the time Terminator 2: Judgment Day entered post-production.
- Popular in scientific computing and CAD
Production Timeline
[edit | edit source]- March 1990: Introduction at $8,969-12,000
- October 1991: Quadra 900 announced as successor
- April 1992: Discontinued after 25-month run
- August 1998: Apple ended official support
Sales estimates suggest 30,000-40,000 units sold, making it relatively rare among Mac II models. High price and specialized architecture limited market penetration despite superior performance.
Design Legacy
[edit | edit source]The IIfx influenced Mac development despite commercial limitations:
Technical Innovations
[edit | edit source]- I/O processors concept evolved into modern coprocessors
- Dual-ported memory presaged later memory architectures
- 40 MHz operation pushed 68030 to practical limits
- L2 cache became standard on subsequent high-end Macs
Architecture Dead-ends
[edit | edit source]- 64-pin SIMMs never used again
- IOPs replaced by integrated controllers
- Black SCSI terminator requirement problematic
- Cost/complexity exceeded market tolerance
Final Assessment
[edit | edit source]The IIfx represented peak 68030 performance but arrived as 68040 systems emerged. Its specialized architecture created compatibility issues while delivering marginal real-world improvements over the IIci with cache. The Quadra 900 and 950 delivered superior performance with standard components, rendering the IIfx's complex architecture obsolete.
Maintenance Resources
[edit | edit source]- Macintosh IIfx General Maintenance – Cleaning and preventive care
- Macintosh IIfx Capacitor Replacement Guide – Critical capacitor replacement
- Macintosh IIfx Troubleshooting – Diagnostic procedures
- Macintosh IIfx Memory Upgrade – 64-pin SIMM specifications
Related Pages
[edit | edit source]- Macintosh IIx – Direct predecessor
- Macintosh IIci – Contemporary mainstream model
- Macintosh Quadra 900 – Direct successor
- Macintosh Quadra 950 – Ultimate 68040 tower
- NuBus – Expansion architecture