Editing Apple II

{{Infobox computer
| name         = Apple II (original)
| image        = [[File:Apple II-IMG 7064.jpg|300px]]
| caption      = An early Apple II with floppy drives and monitor
| developer    = Apple Computer Company (Steve Wozniak)
| manufacturer = Apple Computer Company
| type         = Home / personal computer<ref>{{Cite web|url=https://www.britannica.com/technology/Apple-II|title=Apple II | Encyclopedia Britannica|access-date=2024-06-20}}</ref>
| release_date = April 1977 (West Coast Computer Faire)
| discontinued = May 1979 (replaced by Apple II Plus)<ref>{{Cite web|url=https://apple2history.org/history/ah03.html|title=Apple II History: The Apple II Plus|access-date=2024-06-20}}</ref>
| price        = US$1,298 (4 KB model)<br />US$2,638 (48 KB, two floppies, monitor)<ref>{{Cite web|url=https://www.oldcomputers.net/appleii.html|title=Apple II (original) - Old Computers|access-date=2024-06-20}}</ref>
| units_sold   = ≈ 40,000 (original run)
| cpu          = MOS Technology 6502 @ 1 MHz<ref>{{Cite web|url=https://www.britannica.com/technology/Apple-II|title=Apple II | Encyclopedia Britannica|access-date=2024-06-20}}</ref>
| memory       = 4 KB RAM (standard)<br />Expandable to 48 KB on‑board†<ref>{{Cite web|url=https://www.oldcomputers.net/appleii.html|title=Apple II (original) - Old Computers|access-date=2024-06-20}}</ref>
| storage      = Built‑in 1200‑baud cassette interface<br />Optional 5¼″ Disk II (140 KB) after 1978<ref>{{Cite web|url=https://apple2history.org/history/ah03.html|title=Apple II History: The Disk II|access-date=2024-06-20}}</ref>
| display      = NTSC composite: 40 × 24 text<br />• Low‑res (40 × 48, 16 col)<br />• Hi‑res (280 × 192, 6 col)
| sound        = 1‑bit piezo speaker (toggle via address $C030)<ref>{{Cite web|url=https://www.apple2history.org/history/ah03.html|title=Apple II History: Sound|access-date=2024-06-20}}</ref>
| dimensions   = 15.25 in W × 4.25 in H × 17.5 in D<ref>{{Cite web|url=https://www.oldcomputers.net/appleii.html|title=Apple II (original) - Old Computers|access-date=2024-06-20}}</ref>
| weight       = ≈ 11 lb (5 kg)<ref>{{Cite web|url=https://www.oldcomputers.net/appleii.html|title=Apple II (original) - Old Computers|access-date=2024-06-20}}</ref>
| os           = BASIC in ROM • Apple DOS 3.1 / 3.2 (floppy) • ProDOS (1983+)  <ref>{{Cite web|url=https://apple2history.org/history/ah03.html|title=Apple II History: Operating Systems|access-date=2024-06-20}}</ref>
| predecessor  = [[Apple I]]
| successor    = [[Apple II Plus]]
| model        = A2S001 (4 KB) • A2S002 (16 KB) • A2S003 (48 KB)<ref>{{Cite web|url=https://www.oldcomputers.net/appleii.html|title=Apple II (original) - Old Computers|access-date=2024-06-20}}</ref>
}}
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The '''Apple II'''&nbsp;— often styled '''Apple ][''' — was Apple’s first mass‑market microcomputer and the machine that ignited the late‑1970s home‑computer boom.  Announced at the April 1977 West Coast Computer Faire, it combined color graphics, an integrated keyboard, BASIC in ROM, and '''eight open expansion slots''' in a single plastic enclosure — a radical departure from kit‑based contemporaries.

== Historical Context ==
* '''Trinity of ’77:''' Launching alongside the Commodore PET 2001 and TRS‑80 Model I, the Apple II stood out for its color graphics and open slot bus.  
* '''From hobby to home:''' Ready‑to‑run BASIC and cassette I/O meant buyers could power up and program instantly, fostering a vast hobbyist software scene.  
* '''Disk II revolution (1978):''' Wozniak’s low‑chip‑count floppy controller cut drive cost in half, driving Apple II adoption in business and education.<ref>{{Cite web|url=https://apple2history.org/history/ah03.html|title=Apple II History: The Disk II|access-date=2024-06-20}}</ref>

== Hardware Overview ==
{| class="wikitable" style="width:65%; text-align:center;"
! Sub‑system !! Specification
|-
| CPU || MOS 6502 @ 1.023 MHz (NTSC colour‑subcarrier ÷14)<ref>{{Cite web|url=https://www.oldcomputers.net/appleii.html|title=Apple II (original) - Old Computers|access-date=2024-06-20}}</ref>
|-
| On‑board RAM || 4 KB base (16 × 6116 SRAMs)<br />Sockets for 48 KB using eight 4 KB dynamic RAM banks†<ref>{{Cite web|url=https://www.oldcomputers.net/appleii.html|title=Apple II (original) - Old Computers|access-date=2024-06-20}}</ref>
|-
| ROM || 12 KB (Monitor + Integer BASIC + character generator)
|-
| Graphics || • Text 40 × 24, mixed text/lo‑res line<br />• Low‑res 40 × 48, 16 colors<br />• Hi‑res 280 × 192, 6 colors (+ artifact palette)<ref>{{Cite web|url=https://www.britannica.com/technology/Apple-II|title=Apple II | Encyclopedia Britannica|access-date=2024-06-20}}</ref>
|-
| Expansion || Eight 50‑pin slot connectors (Slots 0‑7)<br />Disk II, serial, 80‑column, language card, etc.
|-
| I/O || • Cassette in/out (mini‑jack) 1200 baud<br />• RF modulator or composite video out<br />• Game port (paddles/joystick)<br />• Speaker toggle ($C030)
|}

† Later “language cards” piggy‑backed in Slot 0 to add 16 KB bank‑switch RAM, giving '''64 KB total''' under DOS 3.3 or Apple Pascal.

=== Motherboard Revisions ===
* '''Rev 0 & 1 (1977):''' 4‑layer PCB, raised power rails; sold through serial ≈ 15,000.  
* '''Rev 4 (1978):''' Cleaner DRAM timing, support for '''Integer/Applesoft BASIC ROM switch'''.  
* '''Rev 7 (1979):''' Last original‑run board — silkscreen “Apple Computer © 1978”.

== Software & Usage ==
* '''Monitor prompt ( '''<code>]</code> ''')''' — power‑up to '''$FF69 Reset'''.  
* '''Integer BASIC''' in ROM; Applesoft BASIC supplied on cassette, later in ROM on II Plus.  
* '''Apple DOS 3.1''' shipped with the Disk II (June 1978), automating LOAD/SAVE/BOOT.  
* '''Notable early titles:''' VisiCalc prototype, Adventureland, Lunar Lander, Apple Star‑Trek.

== Expansion Ecosystem ==
{| class="wikitable" style="width:80%; text-align:center;"
! Slot !! Typical Cards (1977‑79 era)
|-
| 0 || 16 KB Language Card (Pascal) • CP/M Z‑80 (Microsoft SoftCard later)
|-
| 1 || 80‑column video • Parallel printer
|-
| 2 || Serial interface • Modem 300 / 1200 baud
|-
| 3 || Parallel printer (Grappler) • Videx 80‑column
|-
| 4 || Game I/O • Speech Synthesizer
|-
| 5 || [[Disk II]] controller
|-
| 6 || Secondary Disk II (Slot 6 is boot slot by convention)
|-
| 7 || Memory expansion • Hard‑sector floppy • Ethernet (very late)
|}

== Maintenance & Restoration ==
Apple II motherboards are robust but susceptible to:

* '''RAM socket corrosion''' — reseat or replace ICs.  
* [[File:Apple II Logic Board.jpg|thumb|335x335px|Apple II Logic Board]]'''RIFA line filters''' in early Astec PSUs — replace before they “magic smoke.”  
* '''Keyboard foam‑pad failure''' (Datanetics Type B) — modern foam disks restore feel.

Capacitor leakage is rare (all‑through‑hole design), but PSU electrolytics should be re‑formed or replaced after decades in storage.
== Documentation & Schematics ==
* '''Apple II Reference Manual''' (blue cover, 1977) — full schematics, Woz Monitor listings.  
* '''Apple DOS Manual''' (1978) — Disk II architecture, DOS 3.1 commands.  
* '''Apple II Schematics''' — [[Apple II Schematics]]

Scanned PDFs are archived on the [[:Category:Apple Documentation|Apple Documentation]] page.

== General Maintenance ==
{{main|Apple II General Maintenance}}
Regular maintenance of Apple II computers primarily involves reseating chips that aren't making good connections with their sockets, which is the number one problem with early Apple II and Apple II Plus machines. Clean the motherboard and case periodically using appropriate methods. For plastic cases, use a dilute solution of 50% Clorox and 50% water with a washcloth, followed by Pledge for finishing. For internal components, remove all expansion cards and use compressed air to clear dust. Always handle ICs with care using an anti-static mat or anti-static bag, as old chips from the 70s and 80s are particularly susceptible to ESD damage. For keyboards, use an IC chip extractor to remove keycaps safely, then clean with 99% isopropyl alcohol. Store computers in climate-controlled environments to prevent oxidation and component degradation.

== Troubleshooting Guide ==
{{main|Apple II Troubleshooting Guide}}
Common issues include display problems, boot failures, and keyboard malfunctions. If the system won't boot, first remove all expansion cards and reseat every chip on the board, then swap chips of the same type to identify failures. For no display output, check the data bus with an oscilloscope for proper signal levels. Bad RAM chips often cause green squares or bars on screen, particularly in the lowest 16K bank. For non-responsive keys, mark faulty keys during testing, then apply 99% isopropyl alcohol with a squeeze bulb at the key stem edges while repeatedly pressing the key. Use the built-in self-test routines and monitor commands for memory testing. Check power supply voltages - the +12V rail should remain above 11.4V under load, and the +5V should stay above 5V. The R/W line should toggle properly; if it never goes low, check the 74LS257 latches at B6 and B7.

== Capacitor Replacement ==
{{main|Apple II Capacitor Replacement}}
RIFA metallized-paper safety capacitors in Apple II power supplies deteriorate over time and require immediate replacement to prevent catastrophic failure with smoke. Replace the X2 safety capacitors (typically 0.1µF and 0.47µF at 275VAC) every year or two as preventive maintenance. Use polypropylene film capacitors from brands like KEMET or TDK as replacements - never use new RIFA capacitors as they have the same failure mode. The Panasonic ECQ-U2A104KL fits as a direct substitute with 20mm lead spacing. Also check capacitor C7 (220µF 10V), which sits near a power resistor and frequently fails due to heat - replace with a 105°C, 16V rated capacitor. When replacing capacitors, always disconnect power and discharge the power supply completely before working. Use proper safety equipment and never work on energized circuits.

== Technical Details ==
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=== System Architecture at a Glance ===
{| class="wikitable styled-table" style="width:95%; text-align:center;"
! Sub-system !! Apple II Specification (Rev-0 / Rev-01, Apr 1977 – ’78)
|-
| '''CPU''' || MOS '''6502''' @ 1.023 MHz (NTSC color-burst ÷ 14)
|-
| '''Address bus / Data bus''' || 16-bit addr. • 8-bit data ⇒ 64 KB logical space
|-
| '''ROM''' || '''12 KB''' total  
* 2 KB WOZ Monitor (F800–FFFF)  
* 10 KB Apple Integer BASIC (E000–F3FF)  
Rev-0 shipped with 10 KB; later Rev-01 raised to 12 KB
|-
| '''RAM (base)''' || 4 KB DRAM (18 × 4116, 200 ns) — optional 4 KB/16 KB kits
|-
| '''RAM (max, mainboard)''' || '''48 KB''' (three 16 KB banks, address-select jumpers)
|-
| '''Expansion RAM''' || +16 KB "Language Card" (slot 0, 1980) ⇒ 64 KB total
|-
| '''Video''' || • '''Text 40 × 24''' (upper-case, inverse)  
• '''Lo-Res''' 40 × 48 (16 colors)  
• '''Hi-Res''' 280 × 192, 6 colors + NTSC artifact hues  
Shift-register DMA steals cycles every micro-line
|-
| '''Sound''' || One-bit speaker toggled by writing any address in $C030 range (~1 µs click)  
Software PWM enables simple music
|-
| '''Mass Storage''' || 1200-baud cassette interface (port C060/61)  
Disk II controller (1978+) 143 KB 5.25″ GCR
|-
| '''I/O, fixed''' || '''Game I/O''' (paddle/joystick) • '''Cassette IN/OUT''' • '''Composite video''' • '''RF modulator header'''
|-
| '''Expansion''' || '''Eight 50-pin slots (0–7)''' full CPU bus, IRQ, DMA; 3 MHz max load  
Slot 6 pre-wired for Disk II; slot 0 firmware (autostart)
|}

=== Default Memory Map (No Language Card) ===
{| class="wikitable styled-table" style="width:85%; text-align:center;"
|+'''Apple II 48 KB Map'''
! Range (hex) !! Size !! Use
|-
| $0000 – $BFFF || 48 KB || '''User RAM''' (three 16 KB banks)
|-
| $C000 – $C07F || 128 B || '''Peripheral soft-switches''' (keyboard, speaker, paddles)
|-
| $C080 – $C0FF || 128 B || '''Peripheral slot I/O''' (reads/writes to slot 0–7 cards)
|-
| $C100 – $C7FF || 1.5 KB || '''Slot ROMs''' (256 B each × 6)
|-
| $C800 – $CFFF || 2 KB || '''Firmware bank''' (usually Disk II)
|-
| $D000 – $FFFF || 12 KB || '''Integer BASIC & Monitor ROM'''
|}
''Soft-switches'' at $C050–$C057 flip graphics/text, hires/lores, full/half screen, etc.

=== Video Timing & Color Generation ===
{| class="wikitable styled-table" style="width:70%; text-align:center;"
! Parameter !! Value (NTSC)
''/ hi-res /''
|-
| Pixel clock || '''14.31818 MHz / 1''' = 14.318 MHz (color sub-carrier × 4)
|-
| Horizontal total || 455 px (280 active)
|-
| Vertical total || 262.5 lines (192 active)
|-
| Refresh rate || 59.94 Hz
|-
| Color method || 1-bit pairs create 3.58 MHz phase shifts → *artifact* green, purple, orange, blue
|}

=== Expansion Slots — Electrical Pin-out (abridged) ===
{| class="wikitable styled-table" style="width:95%; font-size:85%;"
! Pin !! Signal !! Description !! Pin !! Signal !! Description
|-
| 1 || –12 V || –12 V @ 100 mA || 26 || A4 || CPU address 4
|-
| 2 || +12 V || +12 V @ 400 mA || 27 || A3 || Address 3
|-
| 3 || NMI || Non-Mask Int. in || 28 || A2 || Address 2
|-
| 4 || IRQ || IRQ in || 29 || A1 || Address 1
|-
| 5 || RDY || DMA ready out || 30 || A0 || Address 0
|-
| 6 || PHI0 || 6502 Ø0 out || 31 || D0 || Data 0
|-
| … || … || … || … || … || …
|-
| 50 || GND || Ground return || || ||
|}

Slots source full 1 MHz Φ2 and 14 MHz dot clock for video cards.
[[File:Disk II.jpg|thumb|Apple Disk II]]

=== Disk II (1978) Quick Specs ===
* '''Controller''': 8-bit state-machine in 256-byte PROM (Steve Wozniak)  
* '''Encoding''': Group-Code Recording, 13 sector × 35 tracks → 143,360 bytes  
* '''Transfer rate''': ~15 kB s⁻¹; CPU bit-banged (no DMA)

=== Performance Benchmarks (BYTE Jan 1978) ===
{| class="wikitable styled-table" style="width:65%; text-align:center;"
! Test !! Apple II 4 KB !! TRS-80 I (4 KB) || Comment
|-
| BASIC loop (1000 FOR…NEXT) || 18.8 s || 24.7 s || Integer BASIC faster than TRS Level I
|-
| 16-color Lo-Res fill || 0.21 s || — || Unique color graphics edge
|-
| Cassette load 2 KB || 25 s || 49 s || “Kansas City” 1200 baud beats 500 baud
|}

=== Revision History ===
{| class="wikitable styled-table" style="width:90%;"
! Rev !! Board Marker !! Key Changes
|-
| '''Rev-0''' || 820-0001-00 || No silkscreen, paddle trim pots, noisy video; shipped Apr-Aug 1977 (≈6,000 units)
|-
| '''Rev-01''' || 820-0001-04 || Improved video timing, added color – burst delay line; fall ’77
|-
| '''Rev-02''' || 820-0001-07 || Sockets for 16 KB DRAM, CPU ceramic → plastic; early ’78
|-
| '''Rev-03''' || 820-0001-10 || Pre-wired for Language Card, stronger +5 V regulator; late ’78
|}

=== Notable Engineering Traits & Trivia ===
* '''Floating-bus video DMA''': display circuitry ''steals'' DRAM access on every Φ2 low, imposing deterministic “video glitch” timing exploited by games.  
* '''Annunciator outputs''' (addresses $C04E–$C05B) allow slot cards to flip soft-switches or drive relay boards.  
* '''Speaker click length''' equals one CPU instruction — programmers play music by carefully timed loops.  
* The iconic '''“BEEP!”''' is a 65-cycle loop toggling $C030 at 256 µs intervals.  
* First home computer with full '''color graphics''' on a cheap TV via NTSC artifacting.

== Replica & Emulation Resources ==
* '''Replica II''' — Gerber‑faithful four‑layer re‑creation using modern DRAM.  
* '''AppleWin / LinApple / MAME''' — full‑speed software emulators supporting Integer & Applesoft ROM sets and DOS/ProDOS disk images.

== Legacy ==
The expandable '''slot architecture''', affordable Disk II, and the industry‑shifting spreadsheet '''VisiCalc''' made the Apple II the '''first commercially successful mass‑produced microcomputer''', cementing Apple’s future and inspiring clones worldwide (Franklin Ace, Basis 108, ITT 2020).

=== References ===
<references/>

{{Navbox-AppleVintage|state=collapsed}}

[[Category:Apple Vintage Computers]]