Apple Extended Keyboard II
The Apple Extended Keyboard II (AEK II) was Apple's refined professional keyboard introduced October 15, 1990, as the successor to the Apple Extended Keyboard. First bundled with the Macintosh IIsi, the keyboard maintained the 105-key extended layout while incorporating ergonomic refinements including an adjustable rear foot and quieter mechanical switches. The keyboard utilized Alps SKCM Cream Damped switches as its primary configuration, though variants with Salmon Alps, White Alps, and Mitsumi mechanical switches were produced across four manufacturing facilities. Production continued until 1994 when Apple transitioned to the cost-reduced AppleDesign Keyboard featuring rubber dome switches.
| Apple Extended Keyboard II | |
|---|---|
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| Apple Extended Keyboard II M3501 with Alps SKCM Cream Damped switches | |
| Manufacturer | Apple Computer, Inc. |
| Type | Computer keyboard |
| Discontinued | 1994 |
| Price | US$163 (retail) |
| Interface | Apple Desktop Bus |
| Compatible | All ADB-equipped Macs, Apple IIGS |
| Dimensions | 475 mm W × 196 mm D × 41 mm H (maximum) |
| Weight | 1.73 kg (3.81 lbs) |
| Predecessor | Apple Extended Keyboard (M0115) |
| Successor | AppleDesign Keyboard (M2980) |
| Model | M3501, M0312 |
Design Philosophy
The Extended Keyboard II emerged from a collaborative design effort initiated in 1988 when Apple Ireland commissioned Design ID, a Limerick-based industrial design consultancy. Bryan Leech and Peter Sheehan developed initial concepts focusing on ergonomic improvements mandated by emerging European workplace standards. The design team implemented what they termed an "S-curve profile" - a compound curve that positioned the function keys on a flattened plane while maintaining an upward slope through the alphanumeric section.
This profile contrasted with the original Extended Keyboard's continuous convex curve. The new design eliminated the deep case cavity behind the function keys, reducing material usage while maintaining structural integrity. Steven Peart from frogdesign contributed supplementary industrial design work focusing on Design for Manufacture and Assembly (DFMA) principles. Dexter Francis served as Apple's in-house project lead from the Peripheral Products Group.
The first working prototype was constructed at Design ID by Richard Howe, Donal Ryan, and John Fitzgerald. The team specified quieter switch mechanisms after extensive testing revealed the dampened Alps variants met acoustic requirements for office environments while preserving tactile feedback quality.
Physical Construction
Case Design
The AEK II case employed a two-piece construction with distinctive ergonomic features:
- Upper housing: S-curve profile with integrated key wells
- Lower housing: Flat base with retractable adjustment mechanism
- Material: ABS plastic in Platinum gray (Pantone 429C)
- Finish: Textured matte surface matching Snow White design language
- Apple logo: Relocated to upper left corner (from lower left on M0115)
Adjustable Foot Mechanism
A single retractable bar spanning the keyboard width provided typing angle adjustment:
- Retracted position: 6° typing angle
- Extended position: 11° typing angle
- Construction: Reinforced ABS with internal spring mechanism
- Common issue: Mechanism frequently seized due to plastic deformation
Template Posts
Two cylindrical posts flanked the function key row:
- Height: 12mm above case surface
- Diameter: 5.5mm
- Purpose: Secure application-specific function key overlays
- Material: Injection-molded ABS matching case color
Internal Structure
- Mounting plate: 1.5mm steel, powder-coated black
- PCB layers: Double-sided with surface-mount components
- RF shield: Black conductive liner between PCB and lower case
- Stabilizer system: Alps-specific wire stabilizers with plastic clips
Model Variants
M3501 (Primary Model)
Production: 1990-1994
- Markets: Worldwide distribution
- Manufacturing: USA, Mexico, Ireland, Japan
- Switch types: All variants produced
- FCC ID: BCGM3501
M0312 (Early Variant)
Production: 1990-1992
- Markets: North America primarily
- Manufacturing: USA, Mexico
- Switch types: Cream damped Alps exclusively
- FCC ID: BCGM0312
- Note: Some M3501 units carry M0312 serial suffixes
Manufacturing Facilities
United States Production
Location: Fremont, California
- Period: 1990-1994
- Switch types: Cream damped, Salmon Alps
- Serial prefix: Various
- Market focus: North American distribution
Mexico Production
Location: Manufacturing facility details limited
- Period: 1991-1994
- Switch types: Cream damped Alps
- Copyright markings: 1991, 1995
- Market focus: North American distribution
Ireland Production
Location: Cork facility
- Period: 1989-1995
- Switch types: Cream damped Alps exclusively
- Serial characteristics: No 'S' dampener symbol
- Market focus: European distribution
Japan Production
Location: Mitsumi Electric facilities
- Period: 1989-1991
- Switch types: Mitsumi standard mechanical only
- PCB manufacturer: Mitsumi
- Market focus: Asian markets, limited distribution
Switch Technologies
Alps SKCM Cream Damped (Primary)
Specifications:
- Type: Tactile, dampened
- Actuation force: 70g ± 10g
- Pre-travel: 2.0mm
- Total travel: 3.5mm
- Dampening: Rubber bumpers on slider sides
- Sound signature: Muted "thock"
- Lifespan: 10 million actuations
The Cream damped switches represented Alps Electric's response to workplace noise concerns. Small rubber inserts on either side of the slider cushioned both downstroke and upstroke impacts, creating a quieter typing experience while maintaining the tactile characteristics of the SKCM design. The dampening mechanism positioned the tactile point higher in the travel, occasionally leading users to mistake these for rubber dome switches.
Alps SKCM Salmon
Specifications:
- Type: Tactile, non-dampened
- Actuation force: 70g ± 10g
- Pre-travel: 2.0mm
- Total travel: 3.5mm
- Sound signature: Sharp "click-clack"
- Production: USA facilities only
Salmon Alps switches appeared exclusively in USA-manufactured units. These switches lacked the rubber dampeners of the Cream variant, producing a more pronounced acoustic signature with harder bottom-out characteristics. The tactile leaf design remained identical to Cream switches, providing similar actuation feel without sound dampening.
Alps SKCM White Damped
Specifications:
- Type: Tactile, dampened
- Actuation force: 70g ± 10g
- Slider color: Pure white (versus cream)
- Production: Rare variant, USA/Mexico
- Tactile leaf: Modified design from Cream
White damped Alps represented a rare production variant with pure white sliders. While mechanically similar to Cream damped switches, the internal tactile leaf employed a slightly different geometry. Users report virtually identical typing feel despite the mechanical differences.
Mitsumi Standard Mechanical
Specifications:
- Type: Linear to faintly tactile
- Actuation force: 65g ± 10g
- Slider compatibility: Alps mount
- Color: All-white construction
- Production: Japan exclusively
Mitsumi switches appeared only in Japanese-manufactured units. These switches utilized Alps-compatible keycap mounts while employing a simplified internal mechanism. The switches exhibited minimal tactility, operating nearly linearly with significantly reduced acoustic output compared to Alps variants.
Alps SKCL Lock (Caps Lock)
All variants utilized the Alps SKCL Lock switch for Caps Lock:
- Mechanism: Physical latching system
- Housing color: Dark gray (Cream/White keyboards) or Cream (Salmon keyboards)
- Operation: Mechanical lock-down when engaged
- Acoustic: Distinctive click on state changes
Technical Specifications
Physical Dimensions
- Width: 475mm (18.7 inches)
- Depth: 196mm (7.7 inches)
- Height (front): 25mm (1.0 inch)
- Height (rear, foot retracted): 41mm (1.6 inches)
- Height (rear, foot extended): 58mm (2.3 inches)
- Weight: 1.73kg (3.81 lbs)
- Cable length: 1.2m coiled (extends to 1.8m)
Electrical Specifications
- Interface: Apple Desktop Bus (ADB)
- Connectors: Two 4-pin mini-DIN ports (left and right)
- Power consumption: 25mA typical, 50mA maximum
- Operating voltage: 4.75V - 5.25V DC
- Data rate: 10 kbit/s maximum
- Bus addressing: Default address $2
ADB Implementation
- Device handler ID: $02 (standard), $03 (extended protocol)
- Polling rate: 100 Hz maximum
- Key rollover: 2-key minimum guaranteed, 6-key typical
- Communication: Bidirectional serial protocol
Register Configuration
Register 0: Key event buffer
- 2-byte buffer for simultaneous key events
- 7-bit keycode + 1-bit press/release flag
Register 1: Reserved
Register 2: LED and modifier status
- Bit 0: Num Lock LED
- Bit 1: Caps Lock LED
- Bit 2: Scroll Lock LED
Register 3: Device configuration
- Handler ID selection
- Service request flags
Internal Design
PCB Architecture
Controller: Toshiba TC4515BP binary controller
- 8-bit microcontroller
- Integrated ADB protocol handling
- Key matrix scanning at 1000 Hz
- Debounce processing
Component layout:
- Surface-mount technology throughout
- Dual ADB ports on separate daughter boards
- Ribbon cable interconnects
- Component count: ~35 discrete parts
Assembly Process
- Steel plate preparation and powder coating
- Switch insertion into plate (105 positions)
- PCB alignment and mounting to plate assembly
- Wave soldering of switch pins
- Manual installation of stabilizers
- ADB port PCB installation
- Case assembly (front clips, rear tabs)
- Cable routing and strain relief
- Quality control testing
Key Matrix Design
- Matrix size: 8×16 (128 possible positions)
- Ghost key prevention: Diode per switch
- Scan rate: 1000 Hz internal, 100 Hz ADB report
- Debounce period: 5ms typical
Keycap Specifications
Materials and Manufacturing
- Alphanumeric keys: PBT plastic
- Spacebar: ABS plastic (yellowing prone)
- Manufacturing: Dye sublimation
- Thickness: 1.3mm average
- Surface texture: Fine matte finish
Profile Characteristics
The AEK II employed Apple's proprietary keycap profile:
- Function row: Vertical stem mounting, tallest profile
- Number row: Standard height reference
- QWERTY row: 1mm lower than number row
- Home row: 2mm lower than number row
- Bottom row: 3mm lower than number row
- Spacebar: Custom sculpted, centered dip
This profile appeared shifted one row downward compared to standard Cherry or OEM profiles, with keycap skirts matching the keyboard's curved upper surface.
Typography
- Font: Univers 57 Oblique
- Application: Dye sublimated in dark gray
- Alignment: Centered on all keys
- Special keys: Text labels rather than symbols
- Language variants: ISO layouts used local language labels
Serial Number Format
Standard Format
Structure: PPYWWNNNNNN-MODEL
- PP: Plant code
- Y: Year digit (0=1990, 1=1991, etc.)
- WW: Week number (01-52)
- NNNNNN: Sequential unit number
- MODEL: M3501 or M0312 suffix
OEM Identification
First letter indicates manufacturer:
- A: Alps Electric
- M: Mitsumi Electric
Dampener Indicator
Units with 'S' symbol in square on label indicate dampened switches (USA/Mexico only).
Software Compatibility
Operating System Support
- Classic Mac OS: System 6.0.7 through Mac OS 9.2.2
- Mac OS X: 10.0 through 10.3 (with adapters)
- A/UX: Full native support
- Apple IIGS: GS/OS and ProDOS compatible
- BeOS: Third-party driver available
- Linux: Kernel support on PowerPC and x86 (with adapter)
Extended Protocol Features
Handler ID $03 enabled:
- Left/right modifier key differentiation
- Extended function key support (F13-F15)
- Programmable key repeat rates
- Enhanced key event reporting
Special Key Functions
- Power key: Direct system power control
- Command-Control-Power: Force restart
- Command-Option-Escape: Force quit dialog
- Command-Option-P-R: PRAM reset (at startup)
Common Issues and Solutions
Mechanical Problems
| Problem | Cause | Solution | Difficulty |
|---|---|---|---|
| Adjustment bar stuck | Plastic deformation | Disassemble and lubricate mechanism | Moderate |
| Key chatter/repeat | Switch contact oxidation | Clean with isopropyl alcohol | Easy |
| Dead keys | Failed switch | Replace individual switch | Moderate |
| Stabilizer rattle | Worn clips | Replace stabilizer clips | Moderate |
| Case yellowing | UV exposure, brominated flame retardants | Retrobright treatment | Moderate |
| ADB not recognized | Cable damage | Test continuity, replace cable | Difficult |
| Intermittent connection | Corroded ADB pins | Clean with contact cleaner | Easy |
Adjustment Mechanism Restoration
The height adjustment mechanism commonly seized due to plastic stress:
- Remove bottom case screws
- Extract spring from adjustment bar
- Apply silicone lubricant to pivot points
- Work mechanism repeatedly to distribute lubricant
- Reassemble with spring properly seated
Switch Maintenance
Basic cleaning:
- Remove keycap with wire puller
- Apply 3-5 drops 90%+ isopropyl alcohol
- Actuate switch 20-30 times
- Allow 10 minutes evaporation
- Test and repeat if necessary
Deep cleaning (requires desoldering):
- Desolder switch from PCB
- Open housing (4 retention tabs)
- Clean contacts with alcohol
- Inspect spring and leaf condition
- Apply dielectric grease to slider rails
- Reassemble and test before resoldering
Disassembly Procedure
Required Tools
- Phillips screwdriver #1
- Plastic spudgers
- Keycap puller (wire type preferred)
- Isopropyl alcohol 90%+
- Cotton swabs
- Anti-static mat
Step-by-Step Process
Case separation:
- Remove four Phillips screws from bottom
- Note screw lengths (rear screws longer)
- Release ADB port PCBs using spudger
- Push ribbon cables up through slots
- Separate case halves carefully
PCB removal:
- Press two retention tabs backward with thumbs
- Lift PCB assembly while pressing tabs
- Clear five front edge clips
- Remove complete plate/PCB assembly
Adjustment mechanism:
- Remove spring from adjustment bar
- Do not disassemble pivot mechanism
- Clean and lubricate if stuck
Modern Usage
ADB to USB Conversion
Hardware solutions:
- Griffin iMate: Original solution (discontinued, incompatible past Mac OS 10.3)
- Wombat: Current recommended adapter, bidirectional support
- TMK Converter: Open-source DIY option
- Drakware ADB2USB: Commercial cable solution
Conversion considerations:
- Power key requires remapping on modern systems
- Extended protocol features lost in translation
- Typical latency: 1-2ms with quality adapters
- Full NKRO not supported due to ADB limitations
Restoration Best Practices
Retrobrighting procedure:
- Solution: 12% hydrogen peroxide cream
- Application: Even coating avoiding labels
- UV exposure: 6-8 hours with rotation
- Temperature: 20-25°C optimal
- Expected results: 60-80% yellowing reduction
Keycap restoration:
- Cleaning: Warm water with denture tablets
- Soak duration: 4-6 hours maximum
- Stubborn stains: Soft brush with dish soap
- Avoid: Acetone, bleach, or abrasive cleaners
Market Value and Collecting
Current Market Prices (2024)
| Condition | Cream Damped | Salmon Alps | White Damped | Mitsumi |
|---|---|---|---|---|
| Poor (yellowed, worn) | $75-125 | $100-150 | $125-175 | $50-75 |
| Good (functional, some yellowing) | $125-200 | $150-250 | $175-275 | $75-125 |
| Excellent (minimal yellowing) | $200-350 | $250-400 | $275-425 | $125-200 |
| Mint (no yellowing, boxed) | $350-500 | $400-600 | $425-650 | $200-300 |
Authentication Guidelines
- Verify model number on bottom label
- Check serial number format consistency
- Confirm switch type via keycap removal
- Inspect stabilizer clip colors (era-specific)
- Verify template posts present and intact
- Look for dampener symbol if applicable
Preservation Recommendations
- Storage temperature: 15-25°C
- Relative humidity: 40-60%
- Avoid direct sunlight exposure
- Store flat with keys facing up
- Use dust cover or sealed bag
- Maintain cable without tight coiling
Production Statistics
Based on serial number analysis and community data:
- Total production: Estimated 2.5 million units
- Cream damped: ~70% of production
- Salmon Alps: ~15% of production
- White damped: ~5% of production
- Mitsumi: ~10% of production
- Survival rate: Estimated 20-25% functional
Design Legacy
The Apple Extended Keyboard II established several lasting precedents:
Ergonomic innovations:
- Adjustable typing angle became standard
- S-curve profile influenced later designs
- Quieter switches for office environments
Construction standards:
- Steel plate mounting remained premium standard
- Modular assembly improved serviceability
- Quality benchmarks for keycap materials
Market influence:
- Final Apple mechanical keyboard
- Defined expectations for professional keyboards
- Influenced modern mechanical keyboard revival
The AEK II's reputation as Apple's finest keyboard stems from its balance of tactile excellence, build quality, and acoustic refinement. While the original Extended Keyboard's Orange Alps switches achieved legendary status among enthusiasts, the AEK II's Cream damped switches proved more practical for professional environments where the keyboard found widespread adoption.
Comparison with Contemporary Keyboards
| Feature | Apple Extended II | IBM Model M (1391401) | Northgate OmniKey Ultra |
|---|---|---|---|
| Switches | Alps SKCM Cream Damped | Buckling Spring | Alps SKCM Blue/White |
| Weight | 1.73 kg | 2.3 kg | 2.0 kg |
| Keys | 105 | 101 | 104 |
| Interface | ADB | PS/2 | AT/PS/2 switchable |
| Price (1990) | $163 | $179 | $169 |
| Sound level | Quiet | Very Loud | Loud |
| Adjustable angle | Yes | No | Yes |
Cultural Impact
The Apple Extended Keyboard II achieved iconic status as the pinnacle of Apple keyboard design before the transition to cost-reduced rubber dome mechanisms. Its association with professional Macintosh systems throughout the early 1990s established lasting appeal among creative professionals in desktop publishing, graphic design, audio production, and software development.
Recording studios, design agencies, and publishing houses continued using AEK II keyboards well into the 2000s, long after ADB interfaces disappeared from Apple hardware. The keyboard's reputation for reliability meant functional units remained in service for decades, often outlasting multiple computer generations through adapter use.
The mechanical keyboard revival of the 2010s renewed interest in the AEK II, particularly units with less common switch variants. The Matias Tactile Pro and Quiet Pro keyboards, introduced in the 2000s, explicitly positioned themselves as spiritual successors to the Extended Keyboard lineage, using Alps-inspired Matias switches designed to replicate the typing experience.
See Also