Apple IIe Machine Hub
Unenhanced, Enhanced & Platinum Apple //e workbench reference — Astec PSU RIFA alert, 6502/65C02/65C816 architecture, Slot 1–7 & Aux 80-Column guide, self-test codes, and F6–F13 DRAM locator.
Astec / Dyna-Comp PSU RIFA Capacitor Alert & Quad-Rail Check
Inside the long silver/gold metal power supply brick of every Apple II, II Plus, and Apple IIe (most commonly the Astec AA11040 / AA11042 or Dyna-Comp switching supply) sit two amber epoxy RIFA PME 271 M mains filter capacitors (`C1` = 0.1 μF and `C20` = 0.01 μF / 0.047 μF) right behind the IEC mains switch. After 40+ years, their epoxy shells craze, absorb humidity, and detonate with a loud bang and clouds of foul white smoke within minutes of plugging into the wall. Drill out the PSU rivets (or remove the case screws) and replace the RIFA caps with modern 275 V–310 V AC X2 polypropylene safety film caps before powering on!
1 6-Pin Motherboard Power Plug Pinout
The Apple IIe PSU outputs four regulated DC voltages via its 6-pin Molex connector (`J13`):
| Molex Pin | Signal | Target Spec | Primary Use |
|---|---|---|---|
| Pin 1 | GND (0 V) | 0.00 V Return | System Digital Ground |
| Pin 2 | GND (0 V) | 0.00 V Return | System Digital Ground |
| Pin 3 | +5 V DC | 4.85–5.15 V (2.5 A) | CPU, MMU, IOU, 4164 RAM, ROMs & regulation feedback! |
| Pin 4 | +12 V DC | 11.4–12.6 V (1.5 A) | Disk II drive stepper/motor & expansion cards |
| Pin 5 | −12 V DC | −11.4 to −12.6 V (0.25 A) | Super Serial Card RS-232 & analog cards |
| Pin 6 | −5 V DC | −4.75 to −5.25 V (0.25 A) | Expansion slots & Mockingboard/analog audio |
2 Why the Astec PSU "Ticks" Unplugged
- Never test an Astec AA11040 completely unloaded! Because the Astec flyback switching design regulates off the +5 V rail load, turning it on with the 6-pin motherboard plug disconnected causes it to enter an overvoltage hiccup loop — making a rhythmic "tick-tick-tick" chirp with wild voltage readings!
- Bench Dummy Load: To test the PSU outside the Apple IIe, connect a 10 Ω 5 W power resistor (or old 12 V/5 V hard drive) across Pin 3 (+5 V) and Pin 1 (GND) so it draws ~500 mA minimum load.
- Ticking While Plugged Into Motherboard: Indicates a dead short on one of the motherboard rails (most commonly a shorted radial tantalum decoupling capacitor on an expansion card or a shorted 4164 DRAM!). Unplug all Slot 1–7 cards first to isolate.
3 RIFA & Electrolytic Recap Values
- C1 (Across Mains Line):
0.1 μF (100 nF) 275 V AC X2safety film capacitor (15 mm lead pitch). - C20 (Mains Filter):
0.01 μF (10 nF) or 0.047 μF 275 V AC X2/Y2safety capacitor. - Secondary Output Caps: Replace the 1000 μF / 2200 μF 16 V (+5 V filter) and 470 μF 25 V (+12 V filter) axial/radial caps with 105 °C low-ESR capacitors.
- Drop-in Reactive PSU Upgrade: You can also swap the internal PCB inside the original Astec metal shell with a modern ReactiveMicro Universal PSU kit for 85–264 V auto-switching power.
Apple IIe Model Selector & CPU Evolution
Compare the 1983 Unenhanced Apple //e, the 1985 Enhanced Apple //e (65C02 + MouseText), the 1987 Platinum //e, and 65C816 16-bit upgrades.
Unenhanced Apple //e 1983–1985 • 820-0060-A / B • Boots with "Apple ]["
Introduced in January 1983, the Apple //e replaced over 70 discrete TTL chips from the Apple II Plus with two custom Apple LSI chips — the MMU (Memory Management Unit, 344-0010) and IOU (Input/Output Unit, 344-0020) — while adding native uppercase/lowercase keyboard support, 64 KB of single-rail 4164 DRAM on the motherboard, and the dedicated 60-pin Auxiliary Slot for 80-column display and 128 KB total bank-switched memory.
Key ICs & Identification
- Boot Banner: Displays
Apple ][(NOT `Apple //e`) at the top of the screen! - CPU (B4): NMOS MOS / Synertek 6502 @ 1.023 MHz
- MMU (C3): Apple Custom
344-0010(DIP-40) — RAM bank switching, zero page, and slot address decoding - IOU (D5): Apple Custom
344-0020(DIP-40) — video counters, soft-switches, keyboard strobe, speaker & cassette - HAL (B2):
341-0170(16R8 PAL/HAL) — master timing generator - System ROMs (D8 & D10): `CD ROM` (`342-0135-A`, `$C100–$DFFF`) and `EF ROM` (`342-0134-A`, `$E000–$FFFF`)
- Video ROM (D12): `342-0133-A` (2732 4 KB) — lacks MouseText characters (inverse uppercase only)
- Main RAM (F6–F13): 8× 4164 (64K×1, +5 V single-rail) DRAMs
Revision A vs Revision B Motherboard (Double Hi-Res!)
| Board Revision | Part Number | Key Hardware Difference |
|---|---|---|
| Revision A (Early 1983) |
820-0060-A |
Does NOT support Double Hi-Res (560×192 16-colour) graphics! Lacks the Pin 55 (`FRCTXT`) connection on the Auxiliary Slot. Also uses a 6-ROM socket configuration on very early prototypes. |
| Revision B (Mid 1983–1986) |
820-0060-B / 820-0087-A |
Supports full Double Hi-Res graphics when paired with an Extended 80-Column 64K Card (with jumper/molex blocks connected). Can be upgraded to an Enhanced //e in 5 minutes by swapping 4 chips! |
How to Upgrade Any Rev B //e to Enhanced //e: Simply swap out the 4 socketed chips in the official Apple Enhancement Kit: CPU (→ CMOS `65C02`), CD ROM (→ `342-0304-A`), EF ROM (→ `342-0303-A`), and Video ROM (→ `342-0265-A` with MouseText)!
Enhanced Apple //e & 65C816 16-Bit Upgrades 1985–1987 • Boots with "Apple //e"
Released in March 1985 for compatibility with the Apple IIc and ProDOS 8 GUI software (such as AppleWorks, MouseDesk, and GEOS). Upgrades the processor to the low-power CMOS WDC / NCR / Rockwell 65C02 (adding 27 new opcodes including `BRA`, `PHX`, `PHY`, `STZ`), adds the 32 MouseText graphical UI icons to the Video ROM, and improves the Monitor/80-column firmware (`mini-assembler` included at `!` prompt!).
6502 vs 65C02 vs 65C816 CPU Breakdown
| CPU | Architecture | Apple IIe Role & Compatibility |
|---|---|---|
| MOS 6502 (Unenhanced //e) |
8-bit NMOS (1.023 MHz) | Original processor. Supports unofficial/undocumented NMOS opcodes used by a few early 1980–82 copy-protected games, but cannot run ProDOS 2.x or MouseDesk. |
| WDC 65C02 (Enhanced //e) |
8-bit CMOS (1.023 MHz) | Required for Enhanced //e! Adds `STZ`, `BRA`, `PHX/PLX`, bit manipulation opcodes, and fixes the 6502 indirect `JMP ($xxFF)` page-boundary bug. Note: Modern WDC `W65C02S` (with `S` suffix) needs Pin 36 (`BE` Bus Enable) tied to +5 V! |
| WDC 65C816 / 65802 (16-Bit Upgrade / TransWarp / IIgs) |
8/16-bit CMOS (1–14 MHz) | The 16-bit processor of the Apple IIgs (24-bit 16 MB addressing, 16-bit registers, hardware Emulation Mode `E=1` for 100% 65C02 compatibility). Fitted to Apple IIe systems via 40-pin 65802 drop-in CPU, Applied Engineering TransWarp, or Zip Chip / FASTChip accelerators! |
80-Column vs Extended 80-Column (64K Aux) Card
The single 60-pin socket near the front-left of the motherboard (AUXILIARY SLOT, NOT Slot 3!) accepts one of two cards:
- Standard 80-Column Text Card (1 KB RAM): Only holds 1 KB of static/dynamic RAM — enables 80-column text, but leaves the machine at 64 KB total RAM (no Double Hi-Res, no ProDOS `/RAM` drive).
- Extended 80-Column Text Card (`820-0067` — 64 KB RAM): Populated with eight 4164 DRAMs, bringing the Apple IIe to 128 KB total RAM, enabling 560×192 16-colour Double Hi-Res graphics, AppleWorks expanded desktop, and a 64 KB ProDOS `/RAM` disk!
- Modern RAMWorks III / VGA Aux Cards: Plug into the 60-pin Aux slot to expand an Apple IIe up to 1 MB–8 MB of banked RAM or provide lag-free HDMI/VGA output (e.g. A2DVI / RGBtoHDMI).
Apple IIe Platinum 1987–1993 • 820-0188-A • Built-in Numeric Keypad
The final, longest-lived evolution of the Apple IIe, finished in Apple's late-1980s "Platinum" warm grey to match the Apple IIgs and Macintosh SE. Features a redesigned keyboard with a built-in numeric keypad, relocated RESET key at the top-center, and a heavily condensed motherboard that reduces the chip count from 31 ICs down to just 17 ICs!
Cost-Reduced Platinum Motherboard Changes
- Main RAM (2 Chips Instead of 8): Replaces the eight 4164 DRAMs with just two 4464 (64K×4, DIP-18) DRAMs (`UA5` & `UA6`)
- Single 16 KB Combined System ROM: Combines the `CD` and `EF` ROMs into a single 28-pin 27C128 (`342-0349-A`) (`CF ROM`)
- 8-Bit Video ROM: Uses a 28-pin 2764 (`342-0265-A` / `341-0160`)
- Onboard 64K Aux Card Included: Shipped from the factory with a compact 2-chip (`4464`) 64 KB Extended 80-Column Card already installed in the Aux slot
Keyboard Switch Types Across Apple IIe Models
| Keyboard Type | Switch Mechanism | Bench Repair Notes |
|---|---|---|
| Alps SKCC Tall Stem (Most 1983–85 //e) | Mechanical gold/silver leaf contact | Very reliable; flush stuck switches with DeoxIT D5 and compressed air. |
| SMK Vintage Linear | Mechanical metal leaf switch | Crispy linear feel; check for cracked solder joints on the 26-pin keyboard ribbon header. |
| Mitsumi / Alps SKCL (Platinum //e) | Tactile/linear mechanical | Uses a different 26-pin keyboard encoder matrix ROM (`341-0348-A`) to map the numeric keypad! |
Expansion Slot 1–7 Conventions & 50-Pin Bus Pinout
Standard Apple IIe peripheral card slot assignments, memory-mapped I/O decoding, and 50-pin edge connector pinout.
Standard Apple IIe Slot 1–7 Card Map
While the seven 50-pin peripheral slots on the back of the motherboard are electrically nearly identical (except Slot 3 and Slot 7), Apple DOS 3.3, ProDOS, and games expect cards in specific standard slots:
| Slot | Device I/O (`$C0n0`) | Slot ROM (`$Cn00`) | Standard Card Assignment |
|---|---|---|---|
| AUX SLOT (60-Pin, Front-Left) | Soft-switches `$C000–$C00F` | Shares internal `$C300` / `$C800` | Extended 80-Column 64K Text Card (or RAMWorks III / RGB video card). Never plug a 50-pin card here! |
| Slot 1 | $C090–$C09F | $C100–$C1FF | Parallel Printer Card (Grappler+ / Apple Parallel Printer Interface) |
| Slot 2 | $C0A0–$C0AF | $C200–$C2FF | Super Serial Card (SSC) — RS-232 modem, ADTPro disk transfer, or serial printer |
| Slot 3 | $C0B0–$C0BF | $C300–$C3FF (Internal 80-Col ROM) | Leave EMPTY when using an Aux 80-Column Card! (Or used for No-Slot Clock / Uthernet II in I/O-only mode) |
| Slot 4 | $C0C0–$C0CF | $C400–$C4FF | Mockingboard Sound Card (dual 6522 VIA + dual AY-3-8910 PSG) or AppleMouse II Card |
| Slot 5 | $C0D0–$C0DF | $C500–$C5FF | 3.5″ SmartPort / Liron Drive Controller, CP/M Z80 SoftCard, or second Disk II card |
| Slot 6 | $C0E0–$C0EF | $C600–$C6FF | Primary Disk II / 19-Pin Floppy Controller! Auto-boot scans down from Slot 7 → Slot 6 (`PR#6`). |
| Slot 7 | $C0F0–$C0FF | $C700–$C7FF | CFFA3000 / BOOTi / FujiNet / ProDOS Hard Drive / Accelerator Card. (Also carries unique `SYNC` and `COLOR REF` video pins on Pins 35 & 19!). |
CRITICAL EDGE CONNECTOR RULE: Every Apple II expansion card has an arrow or component-side marking that MUST point toward the front keyboard (Pin 1 = Front Left, Pin 25 = Rear Left, Pin 26 = Rear Right, Pin 50 = Front Right). Inserting a Disk II or Mockingboard backwards will instantly short +12 V/−12 V into the 6502 address bus and destroy the MMU!
50-Pin Peripheral Expansion Slot Pinout Slots 1–7 • 0.1″ Pitch
Pins 1–25 run Front-to-Back along the Left (Component) side; Pins 26–50 run Back-to-Front along the Right (Solder) side:
| Left Pin | Signal | Right Pin | Signal |
|---|---|---|---|
| 1 | /IOSEL (`$Cn00–$CnFF` ROM Select) | 50 | −12 V DC |
| 2 – 17 | A0 – A15 (Address Bus) | 49 – 42 | D0 – D7 (Data Bus: 49=D0 … 42=D7) |
| 18 | R/W (Read = High, Write = Low) | 41 | /DEVSEL (`$C0n0–$C0nF` I/O Strobe) |
| 19 | NC (Slot 7 only: `SYNC`) | 40 | Φ0 (1.023 MHz CPU Phase 0 Clock) |
| 20 | /IOSTB (`$C800–$CFFF` Shared ROM) | 39 | μPSYNC (6502 Opcode Fetch Sync) |
| 21 | RDY (CPU Ready / Wait) | 38 | Φ1 (Phase 1 Clock) |
| 22 | /DMA (Direct Memory Access Request) | 37 | Q3 (2.046 MHz Asymmetric Clock) |
| 23 | INT OUT (Daisy-chain Interrupt Out) | 36 | 7M (7.159 MHz Clock) |
| 24 | DMA OUT (Daisy-chain DMA Out) | 35 | NC (Slot 7 only: `3.58MHz COLOR REF`) |
| 25 | +5 V DC | 34 | −5 V DC |
| — Rear of Slot — | 33 | +12 V DC | |
| 26 | GND (0 V) | 32 | /INH (Pull low to disable motherboard RAM/ROM) |
| 27 | DMA IN (Daisy-chain DMA In) | 31 | /RES (System Reset, active-low) |
| 28 | INT IN (Daisy-chain Interrupt In) | 30 | /IRQ (Maskable Interrupt Request) |
| 29 | /NMI (Non-Maskable Interrupt) | — | — |
Built-in Self-Test & 4164 DRAM Fault Locator
Running the onboard Apple IIe diagnostic routine and decoding `RAM:` bit errors or boot screen character corruption directly to chips F6–F13.
Built-in Apple IIe Hardware Self-Test Routine
Every Apple IIe (with `CD` and `EF` ROMs) contains a built-in hardware diagnostic suite in ROM that tests the MMU, IOU, Zero Page, and all 64 KB of main RAM (plus 64 KB of Aux RAM if installed)!
How to Launch the Self-Test
- Keyboard Shortcut: Hold down CONTROL + OPEN-APPLE ( outline) + CLOSED-APPLE ( solid) simultaneously, then press and release RESET before releasing the Apple keys.
- No-Keyboard Trick: Simply remove the 26-pin keyboard ribbon cable (or remove the Aux 80-column card if the diagnostic jumper is set) and turn on the power — with both Apple-key sense lines floating high (same as holding both Apple keys down!), the Apple IIe automatically launches the self-test!
Decoding Self-Test Results
| Screen Message | Meaning & Faulty Component |
|---|---|
KERNEL OK(or SYSTEM OK on Enhanced //e) | 100% Pass! Main 64K RAM, Aux 64K RAM, MMU, and IOU soft-switches all passed. |
* RAM ZP 0 0 1 0 0 0 0 0(8 binary digits: Bit 7 → Bit 0) | Mainboard 4164 DRAM Failure! A `1` in any of the 8 positions indicates which data bit (`D7` on left down to `D0` on right) failed during the Zero-Page / Main RAM test. See the F6–F13 locator table opposite! |
* RAM AUX 0 0 0 0 1 0 0 0 | Faulty 4164 DRAM on the Extended 80-Column Aux Card! Unplug the Aux card and re-run the test to confirm the motherboard passes `KERNEL OK`. |
MMU <code> / IOU <code> | Failed soft-switch or bank-latch inside the custom MMU (`344-0010` at C3) or IOU (`344-0020` at D5). Clean and reseat their 40-pin sockets first! |
Garbled Text & 4164 DRAM Chip Locator (F6–F13)
Because the 40-column text screen (`$0400–$07FF`) is stored directly in Main RAM and constantly refreshed by the IOU/MMU, a single dead 4164 DRAM (F6–F13) turns the blank screen (`$A0` = normal space, `1010 0000` binary) into a grid of repeating characters even if the CPU can't boot!
| Data Bit | IIe Board IC (8-Chip Board) |
Platinum IC (2-Chip 4464) |
Self-Test Bit Position (Left → Right) |
Screen Character If Stuck |
|---|---|---|---|---|
| Bit 0 (D0) | F6 (Leftmost) | UA5 (Pin 2) | 0 0 0 0 0 0 0 1 | ! (`$A1` if stuck HIGH) |
| Bit 1 (D1) | F7 | UA5 (Pin 3) | 0 0 0 0 0 0 1 0 | " (`$A2` if stuck HIGH) |
| Bit 2 (D2) | F8 | UA5 (Pin 15) | 0 0 0 0 0 1 0 0 | $ (`$A4` if stuck HIGH) |
| Bit 3 (D3) | F9 | UA5 (Pin 17) | 0 0 0 0 1 0 0 0 | ( (`$A8` if stuck HIGH) |
| Bit 4 (D4) | F10 | UA6 (Pin 2) | 0 0 0 1 0 0 0 0 | 0 (`$B0` if stuck HIGH) |
| Bit 5 (D5) | F11 | UA6 (Pin 3) | 0 0 1 0 0 0 0 0 | @ (`$80` if stuck LOW) |
| Bit 6 (D6) | F12 | UA6 (Pin 15) | 0 1 0 0 0 0 0 0 | Flashing characters (`$60` if stuck LOW) |
| Bit 7 (D7) | F13 (Rightmost) | UA6 (Pin 17) | 1 0 0 0 0 0 0 0 | Inverse white blocks (`$20` if stuck LOW) |
Bench Tip — Micron MT4264 Warning: If your Apple IIe motherboard or Aux 80-Column card has Micron `MT4264` DRAMs soldered in row F, expect multiple failures — socket the entire F6–F13 row and install reliable NEC, Hitachi, or TI 4164-15 chips!
Composite Video, Game I/O & Cassette Pinouts
RCA Composite NTSC/PAL video output tips, rear DE-9 Joystick port, and internal 16-pin DIP Game I/O socket.
RCA Composite Video Out & NTSC Artifact Colour 1 V p-p 75 Ω
The Apple IIe outputs baseband composite video directly on its rear yellow/metal RCA phono jack (`J15`). Unlike the C64 or Atari, the Apple II generates colour entirely in the digital domain using 3.579545 MHz NTSC phase-shifted pixel patterns (Wozniak Artifact Colour)!
- Monochrome vs Colour in 80 Columns: In 80-column text mode, pixel transitions occur at 14.318 MHz, which a colour NTSC TV interprets as rainbow colour fringes! On real CRT monitors (like the AppleColor Composite Monitor IIe), press the monitor's front Monochrome / Color button (or use a green-phosphor Apple Monitor II) for razor-sharp 80-column text.
- European PAL Apple IIe Boards (`820-0073`): PAL Apple IIe motherboards include an extra PAL colour encoder circuit and 14.25 MHz crystal. Ensure the onboard 50/60 Hz and Monochrome/Colour links are set appropriately.
- Modern Upscalers (RetroTINK 5X / 4K vs HDMI Cards):
- For the RCA composite jack, the RetroTINK 5X-Pro or 4K includes a dedicated comb-filter decoder that cleanly renders Apple II NTSC artifact colours.
- For pixel-perfect digital HDMI, install an A2DVI / RGBtoHDMI card in Slot 3 or an Aux-slot RGB adapter.
Rear DE-9 Joystick Port & Internal 16-Pin Game I/O
Apple IIe joysticks use 150 kΩ linear potentiometers wired between +5 V and the four `PDL0–PDL3` inputs of a 558 Quad Timer IC (`NE558` at C13). Note: The rear 9-pin D-Sub is NOT Atari-compatible!
| DE-9 Pin | 16-Pin DIP Socket | Signal | Function |
|---|---|---|---|
| Pin 1 | Pin 3 | PB1 (Closed-Apple) | Pushbutton 1 / Solid-Apple key (active-high, internal pull-down) |
| Pin 2 | Pin 1 | +5 V DC | +5 V supply for joystick pots & buttons |
| Pin 3 | Pin 8 | GND (0 V) | System ground |
| Pin 4 | Pin 10 | PDL2 (X2 Axis) | Second joystick X-axis pot (150 kΩ to +5 V) |
| Pin 5 | Pin 6 | PDL0 (X1 Axis) | Primary joystick X-axis pot (150 kΩ to +5 V) |
| Pin 6 | Pin 4 | PB2 | Pushbutton 2 (`$C063` bit 7) |
| Pin 7 | Pin 2 | PB0 (Open-Apple) | Primary Fire Button 0 / Open-Apple key (`$C061` bit 7) |
| Pin 8 | Pin 7 | PDL1 (Y1 Axis) | Primary joystick Y-axis pot (150 kΩ to +5 V) |
| Pin 9 | Pin 11 | PDL3 (Y2 Axis) | Second joystick Y-axis pot (150 kΩ to +5 V) |
Joystick Centering Drift Fix: If the joystick pulls hard to one side or jitters in games, replace the four 0.022 μF (22 nF) timing capacitors (`C4–C7`) and the socketed 16-pin NE558 Quad Timer (C13) on the motherboard!
Chip & EPROM Reference
Interactive IC Pinout Finder links plus Apple custom silicon (MMU, IOU, HAL) and ROM/EPROM substitution guide.
MOS / Synertek 6502
B4 (Unenhanced //e) — Original 1.023 MHz NMOS 8-bit microprocessor.
View Pinout →65C02 (CMOS)
B4 (Enhanced & Platinum //e) — Low-power CMOS 65C02 with 27 additional instructions required by Enhanced ROMs.
View Pinout →4164 DRAM (×8)
F6–F13 (Main) & Aux Card — Single-rail +5 V 64K×1 dynamic RAM chips.
View Pinout →MOS 6522 VIA
Used in pairs on the Mockingboard sound card, Mouse Interface Card, and Z80/6809 co-processor cards.
View Pinout →AY-3-8910 / 8913 PSG
Dual 3-voice stereo sound generators fitted to Apple II Mockingboard and Phasor audio expansion cards.
View Pinout →Apple Custom LSI & Keyboard Encoder Reference
| Chip | Apple Part # | Function & Bench Notes |
|---|---|---|
| MMU (C3) | 344-0010-A / B (NTSC & PAL) |
40-pin DIP Memory Management Unit. Generates `RAS`/`CAS`, manages `$C000–$FFFF` language card RAM banking, and Aux RAM switching. |
| IOU (D5) | 344-0020-A (NTSC)344-0021-A (PAL) |
40-pin DIP Input/Output Unit. Generates video display addresses, sync, speaker toggle (`$C030`), and graphics soft-switches (`$C050–$C057`). |
| HAL (B2) | 341-0170-A (16R8 PAL) |
20-pin High-speed Array Logic dividing the 14.318 MHz master crystal into `Φ0`, `Φ1`, `7M`, `Q3`, and `RAS`/`CAS` timing edges. |
| Keyboard Encoder (E13) | AY-5-3600-PRO (`341-0150`) | 40-pin DIP matrix scanner reading the keyboard via a 2K/4K Keyboard ROM (`341-0132-B` / `D`) at E12. If all keys are dead except Reset & Apple keys, check AY-5-3600-PRO! |
System & Video ROM EPROM Substitution Guide
All four ROM sockets on the standard 1983–86 Apple IIe motherboard (`D8`, `D10`, `D12`, `E12`) use standard 28-pin or 24-pin JEDEC EPROM pinouts — no custom adapters required!
| Socket | Unenhanced Part # | Enhanced Part # | Direct EPROM Drop-In |
|---|---|---|---|
| D8 (CD ROM — 8 KB) (`$C100–$DFFF`) |
342-0135-A / B |
342-0304-A |
27C64 (8 KB, 28-pin) direct drop-in! (Or 27C128 with image burned in upper or both 8K halves). |
| D10 (EF ROM — 8 KB) (`$E000–$FFFF`) |
342-0134-A |
342-0303-A |
27C64 (8 KB, 28-pin) direct drop-in! |
| D12 (Video ROM — 4K/8K) | 342-0133-A (4 KB) |
342-0265-A (US)342-0273-A (UK/PAL) |
2732A (4 KB, 24-pin) or 27C64 (8 KB, 28-pin) depending on motherboard jumper `X6` (`2732` vs `2764` socket). |
| E12 (Keyboard ROM — 2 KB) | 341-0132-B |
341-0132-D |
2716 (2 KB, 24-pin) or 2732A (with 2K image duplicated in both halves). |
Important Note When Fitting a Modern WDC `W65C02S6TPG-14` CPU: Brand-new Western Design Center `W65C02S` chips assign Pin 36 as `BE` (Bus Enable, active-high) and Pin 1 as `/VPB` (Vector Pull Output), whereas the Apple IIe motherboard ties Pin 1 directly to GND! To use a modern `W65C02S` in an Apple IIe: bend out Pin 1 (leave unconnected) and bend out Pin 36 and bridge it to Pin 8 (+5 V VDD) via a 3.3 kΩ resistor (Vintage 1980s `R65C02P2` / `NCR 65C02` chips drop straight in with no pin bending).
Resources & Further Reading
Blog posts, interactive bench tools, and essential Apple II hardware archives.
Smiggy's Apple II & 6502 Posts
Bench Tools & Machine Hubs
- IC Pinout Finder — 6502, 65C02, 4164, 6522, AY-3-8910 & more
- Recap Planner — capacitor replacement guide
- Ohm's Law Calculator
- C64 Machine Hub — Commodore 64 reference
- C128 Machine Hub — C128, C128D & DCR reference
- SX-64 Machine Hub — Executive Portable C64 reference
- Amiga Machine Hub — A500/A600/A1200 reference
- Atari ST Hub — 520ST, 1040STFM & STE reference
- BBC Micro Hub — Model B, B+ & Master 128 reference
- ZX Spectrum Hub — 16K/48K & +2/+3 reference
- Dragon 32/64 Hub — Dragon 32 & 64 reference
- Amstrad CPC 464 Hub — CPC 464 & Datacorder reference
- Sinclair QL Hub — 68008, Microdrive & ULA reference
- Acorn Atom & Electron Hub — Atom & Electron reference
- Osborne 1 & Kaypro II Hub — CP/M luggable reference
- Oric-1 & Atmos Hub — Oric 6502A & ULA reference
- Amstrad CPC 6128 Hub — 128K & 3″ disc reference
- MSX Machine Hub — MSX1, MSX2, MSX2+ & Turbo R reference
- Big-Box Amiga Hub — A1000, A2000, A3000 & A4000 reference
- Atari 8-Bit Hub — 400/800, 800XL & 130XE reference
- VIC-20 Machine Hub — Commodore VIC-20 reference
External Apple IIe Resources
- Asimov Apple II Archive — schematics, ROM dumps, disk images, and SAMS manuals
- ADTPro (Apple Disk Transfer ProDOS) — bootstrap & transfer disks over audio or serial from PC/Mac
- Applefritter Apple II Forum — hardware repair and restoration community
- Understanding the Apple IIe (Jim Sather) — the definitive cycle-by-cycle MMU/IOU hardware bible