Macintosh 128K

2025-07-24T15:21:35Z

47.37.103.116: These are 4264 chips, not 4164

{{Infobox computer
| name = Macintosh 128K
| image = [[File:Macintosh128K.jpg|250px]]
| caption = Macintosh 128K
| manufacturer = Apple Computer, Inc.
| type = Personal Computer
| release date = January 24, 1984
| discontinued = October 1, 1985
| price = US$2,495
| cpu = Motorola 68000 @ 7.83 MHz
| memory = 128 KB RAM (not expandable)
| storage = 400 KB 3.5" floppy drive
| display = 9" monochrome CRT (512×342 pixels)
| sound = Monaural 8-bit, 22 kHz (4-voice)
| dimensions = 13.6" H × 9.6" W × 10.9" D
| weight = 16.5 lbs (7.5 kg)
| os = System 1.0 – System 3.2
| predecessor = None
| successor = [[Macintosh 512K]]
| codename = Annie, Mac, Twiggy Mac
| model = M0001
}}
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The '''Macintosh 128K''' was Apple's first mass-market personal computer to feature a graphical user interface and mouse, released on January 24, 1984.<ref>{{cite web |url=https://www.computerhistory.org/timeline/1984/ |title=1984 Timeline of Computer History |publisher=Computer History Museum |access-date=2025-01-25}}</ref><ref>{{cite web |url=https://americanhistory.si.edu/collections/object/nmah_334371 |title=Apple Macintosh Microcomputer |publisher=National Museum of American History |access-date=2025-01-25}}</ref> Designed to be an affordable and user-friendly computer, the Macintosh 128K was revolutionary in its time but was severely limited by its '''128 KB of RAM''', which was soldered to the logic board and could not be expanded.<ref>{{cite web |url=https://support.apple.com/kb/SP186?locale=en_US |title=Macintosh 128K: Technical Specifications |publisher=Apple Support |access-date=2025-01-25}}</ref> This memory constraint became the system's defining limitation, forcing users into constant "disk swapping" when running applications and preventing the use of more demanding software.<ref>{{cite book |last=Hertzfeld |first=Andy |title=Revolution in the Valley: The Insanely Great Story of How the Mac Was Made |publisher=O'Reilly Media |year=2005 |isbn=0596007191}}</ref>

The system used a '''Motorola 68000 processor running at 7.83 MHz''' and introduced '''3.5-inch floppy drives''' to the personal computer market.<ref>{{cite web |url=http://www.easy68k.com/paulrsm/doc/dpbm68k1.htm |title=Design Philosophy Behind Motorola's MC68000 |author=Thomas W. Starnes |publisher=BYTE Magazine |date=April 1983 |access-date=2025-01-25}}</ref><ref>{{cite book |last=Levy |first=Steven |title=Insanely Great: The Life and Times of Macintosh, the Computer that Changed Everything |publisher=Penguin Books |year=1994 |isbn=0140291773}}</ref> The Macintosh 128K originally shipped with '''System 1.0''', running the bundled MacPaint and MacWrite applications, and could support up to '''System 3.2'''.<ref>{{cite web |url=https://archive.org/details/1984macintoshmanual |title=1984 Macintosh Manual |publisher=Apple Computer, Inc. |year=1984 |access-date=2025-01-25}}</ref> Due to severe memory constraints, applications like '''MacDraw''', '''Microsoft Excel''', and '''PageMaker''' required the later [[Macintosh 512K]] or [[Macintosh Plus]] models. The 128K's limited memory meant that even switching between MacPaint and MacWrite required ejecting and inserting floppy disks multiple times—earning it the nickname "the $2,500 disk swapper" among early users.

== General Maintenance ==
For detailed general maintenance practices including cleaning, PRAM battery handling (not applicable to 128K), connector corrosion prevention, and voltage adjustments, please see the dedicated [[Macintosh 128K/512K General Maintenance]] page.

== PCB Schematics & Service Manual ==

The Macintosh 128K features two primary PCBs: the Logic Board and Analog Board. Below are the detailed schematics and the official Apple service manual. Due to the similarities with the [[Macintosh 512K]], the logic board and analog board are nearly identical, with the 512K using additional RAM chips. The [[Macintosh Plus]] also shares the same analog board design (with the addition of a PRAM battery socket) as the 128K and 512K.

=== Apple Service Manual ===
<pdf width="800" height="500">File:Macintosh 128k.512k.pdf</pdf>

All of the Apple Service Manuals can be found on the [[:Category:Apple Service Source|Apple Service Source]] page.

=== Logic Board & Analog Board Schematics ===

{| class="wikitable" style="width:50%; text-align:center;"
|+'''Macintosh 128K PCB Schematics'''
|-
! style="background-color:#f2f2f2; width:30%;"| Logic Board
! style="background-color:#f2f2f2; width:30%;"| Analog Board
|-
| [[File:Macintosh128K_LogicBoard.jpg|thumb|center|250px|Macintosh 128K Logic Board]][[File:Macintosh128K_LogicBoard_Schematic.jpg|thumb|center|250px|Macintosh 128K Logic Board Schematic]]
| [[File:MacintoshPlus AnalogBoard.jpg|center|thumb|250px|Macintosh 128K Analog Board]][[File:MacintoshPlus AnalogBoard Schematic.jpg|center|thumb|250px|Macintosh 128K Analog Board Schematic]]
|}

== Capacitor Replacement Guide ==
Detailed capacitor replacement guidelines for both analog and logic boards can be found on the [[Macintosh 128K/512K Capacitor Replacement Guide]] page.

== Retrobrite ==
Instructions on addressing case yellowing through Retrobrite treatment can be found on the [[Retrobrite]] page.

== Troubleshooting ==
A comprehensive troubleshooting guide addressing no power, chime but no video, intermittent operation, Sad Mac errors, and floppy drive problems is available on the [[Macintosh 128K/512K Troubleshooting]] page.

== Technical Details ==
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=== System Architecture at a Glance ===
{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Sub-system !! Specification (Macintosh 128K, Jan 1984)
|-
| '''CPU''' || Motorola 68000 @ 7.8336 MHz (15.667 MHz ÷ 2){{cite web |url=http://www.easy68k.com/paulrsm/doc/dpbm68k1.htm |title=Design Philosophy Behind Motorola's MC68000 |author=Thomas W. Starnes |publisher=BYTE Magazine |date=April 1983 |access-date=2025-01-25}}
|-
| '''Bus width''' || '''16-bit data''' • 24-bit address (16 MB logical space)
|-
| '''ROM''' || '''64 KB "Boot/Toolbox"''' — 4 × TMS2532 16 KB mask ROMs{{cite web |url=https://support.apple.com/kb/SP186?locale=en_US |title=Macintosh 128K: Technical Specifications |publisher=Apple Support |access-date=2025-01-25}}
|-
| '''RAM''' || '''128 KB DRAM''' (64 × MT4264-15, 150 ns) — '''non-expandable'''{{cite web |url=https://americanhistory.si.edu/collections/object/nmah_334371 |title=Apple Macintosh Microcomputer |publisher=National Museum of American History |access-date=2025-01-25}}
|-
| '''Video''' || 512 × 342 mono — '''22.1 KB frame buffer''' shared with system RAM<br>Display DMA @ 15.667 MHz steals ~60% of CPU cycles during active scan
|-
| '''Sound''' || 8-bit DAC via VIA Port A • 22.254 kHz PWM → RC filter → speaker
|-
| '''Storage''' || Sony OA-D34V 400 KB GCR 3.5″ drive • IWM controller<br>Variable speed: 394 RPM (outer) → 590 RPM (inner tracks)
|-
| '''Ports''' || DE-9 mouse • DE-9 keyboard • DB-19 ext. floppy • RS-422 serial × 2 • 3.5mm audio
|-
| '''Expansion''' || '''None''' — no slots, non-upgradeable RAM
|}

=== Memory Map (Physical) ===
{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''Macintosh 128K Address Space'''
! Range !! Size !! Purpose
|-
| $000000 – $01FFFF || 128 KB || '''DRAM''' (actual system memory)
|-
| $020000 – $03FFFF || 128 KB || '''DRAM mirrors''' (unused on 128K)
|-
| $400000 – $40FFFF || 64 KB || '''ROM''' (Boot/Toolbox)
|-
| $410000 – $41FFFF || 64 KB || '''ROM mirrors'''
|-
| $600000 – $6007FF || 2 KB || '''VIA 1''' (system timers, sound)
|-
| $800000 – $8007FF || 2 KB || '''VIA 2''' (keyboard, mouse, floppy)
|-
| $A00000 – $A007FF || 2 KB || '''SCC''' (serial communications)
|-
| $C00000 – $C007FF || 2 KB || '''IWM''' (floppy disk controller)
|-
| $E00000 – $EFFFFF || 1 MB || '''Slot space''' (unused on 128K)
|}

*Frame-buffer:* 22,016-byte display buffer at '''$12700 – $1FFFF''' (top of RAM); DMA fetches pixels during active scan, reducing CPU performance by ~40%.

=== ROM Layout (64 KB) ===
{| class="wikitable styled-table" style="width:90%;"
! Offset !! Size !! Module
|-
| $400000 || 4 KB || 68000 exception vectors + Boot code
|-
| $401000 || 16 KB || QuickDraw 1.0 (monochrome bitmap routines)
|-
| $405000 || 24 KB || Macintosh Toolbox (Window/Menu/Dialog Managers)
|-
| $40B000 || 8 KB || SANE (Standard Apple Numeric Environment)
|-
| $40D000 || 6 KB || Sony IWM floppy driver
|-
| $40E800 || 6 KB || System utilities & resource manager
|}

=== Video Timing ===
{| class="wikitable styled-table" style="width:70%; text-align:center;"
! Parameter !! Value
|-
| Pixel clock || 15.667 MHz ÷ 2 = 7.833 MHz
|-
| Horizontal total || 704 pixels (512 active)
|-
| Vertical total || 370 lines (342 active)
|-
| Refresh rate || 60.15 Hz
|-
| Memory bandwidth || ~22 MB/s (shared with CPU)
|}

=== Floppy Disk Format (400 KB Sony GCR) ===
* '''80 tracks''' • single-sided • variable-speed GCR encoding
* '''12 sectors/track''' (outer) decreasing to '''8 sectors/track''' (inner)
* '''Sector size:''' 512 bytes • Total capacity: 409,600 bytes
* '''IWM controller''' with software-controlled stepper motor timing

=== Key I/O ICs ===
* '''6522 VIA × 2''' (MOS Technology) — system timers, sound PWM, I/O handshake<ref>{{cite web |url=http://www.easy68k.com/paulrsm/doc/dpbm68k2.htm |title=Design Philosophy Behind Motorola's MC68000 (Part 2) |author=Thomas W. Starnes |publisher=BYTE Magazine |date=May 1983 |access-date=2025-01-25}}</ref>
* '''8530 SCC''' (Zilog) — dual RS-422 serial ports (230.4 kbps max)
* '''IWM''' (Apple custom) — Integrated Wozniak Machine floppy controller
* '''MC6883 PAL''' (Motorola) — address decode, 60 Hz VBL interrupt generation

=== Sound System ===
68000 writes 8-bit samples to VIA Port A at 22.254 kHz. VIA Timer 1 toggles Port B to create PWM signal, which passes through RC filter (R=10kΩ, C=0.1µF) to internal 8-ohm speaker or rear 3.5mm audio jack.

=== Memory Limitations & Performance Impact ===
The 128K's memory constraint created several operational challenges:
* '''Application switching''' required complete disk swaps due to insufficient RAM
* '''MultiFinder''' (cooperative multitasking) was impossible until 512K model
* '''Virtual memory''' concepts were unused due to single-floppy, no-HDD configuration
* '''System overhead''' consumed ~20KB, leaving only ~100KB for applications and documents

=== Hardware/Easter Facts ===
* First consumer computer to ship with 3.5" Sony floppy drives (later industry standard){{cite book |last=Levy |first=Steven |title=Insanely Great: The Life and Times of Macintosh, the Computer that Changed Everything |publisher=Penguin Books |year=1994 |isbn=0140291773}}
* Hidden startup chime: Hold '''⌘ + Option + Shift + Delete''' during boot for deep bass tone{{cite book |last=Hertzfeld |first=Andy |title=Revolution in the Valley: The Insanely Great Story of How the Mac Was Made |publisher=O'Reilly Media |year=2005 |isbn=0596007191}}
* Logic board manufactured by Apple in Fremont, California facility{{cite web |url=https://www.computerhistory.org/timeline/1984/ |title=1984 Timeline of Computer History |publisher=Computer History Museum |access-date=2025-01-25}}
* Case design influenced by Braun radio aesthetics via Hartmut Esslinger
* '''"Twiggy Mac"''' prototype used dual 5.25" drives before Sony partnership{{cite web |url=https://archive.org/details/OriginalMacBrochure1984 |title=Original Apple Macintosh 128K Brochure 1984 |publisher=Apple Computer |year=1984 |access-date=2025-01-25}}
* Custom Motorola 68000 processors marked "SC87839L" used in development prototypes{{cite web |url=http://www.easy68k.com/paulrsm/doc/dpbm68k1.htm |title=Design Philosophy Behind Motorola's MC68000 |author=Thomas W. Starnes |publisher=BYTE Magazine |date=April 1983 |access-date=2025-01-25}}

== Gallery ==
<gallery mode="packed" heights="180">
File:Macintosh128K.jpg|Macintosh 128K system
File:Macintosh128K LogicBoard.jpg|Logic board (64 × 64Kbit DRAM chips visible)
File:MacintoshPlus AnalogBoard.jpg|Analog board (shared with 512K/Plus)
File:System 2.png|System 2 Desktop
</gallery>

== Related Pages ==
* [[Macintosh 128K/512K General Maintenance]]
* [[Macintosh 128K/512K Troubleshooting]]
* [[Macintosh 128K/512K Capacitor Replacement Guide]]
* [[Macintosh 512K]]
* [[Macintosh Plus]]
* [[CRT Discharge Procedure]]

== References ==
<references />
[[Category:Apple Vintage Computers]]
{{Navbox-AppleVintage}}

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Macintosh 128K