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{{Infobox computer
{{Infobox computer
| name        = Macintosh Classic
| name        = Macintosh Classic
| image        = [[File:Macintosh Classic.jpg|250px]]
| image        = [[File:Macintosh classic.jpg|250px]]
| caption      = Macintosh Classic
| caption      = Macintosh Classic
| manufacturer = Apple Computer, Inc.
| manufacturer = Apple Computer, Inc.
Line 16: Line 16:
| weight      = 16.5 lbs (7.5 kg)
| weight      = 16.5 lbs (7.5 kg)
| os          = System 6.0.7 – System 7.5.5
| os          = System 6.0.7 – System 7.5.5
| predecessor  = [[Macintosh SE]]
| predecessor  = [[Macintosh SE/30]]
| successor    = [[Macintosh Classic II]]
| successor    = [[Macintosh Classic II]]
| codename    = Elsie, Skywriter
| codename    = Elsie, Skywriter
| model        = M0420
| model        = M0420
}}
}}
The '''Macintosh Classic''' was introduced by Apple on October 15, 1990, as a low-cost alternative in the Macintosh lineup and a spiritual successor to the original Macintosh 128K and SE. It retained the same 9-inch monochrome display and compact form factor, but included a 1.44 MB SuperDrive and optional internal SCSI hard drive. It was the first Macintosh to sell for under $1,000, making it a popular choice for schools and home users.
The '''Macintosh Classic''' was introduced by Apple on October 15, 1990, as a low-cost alternative in the Macintosh lineup and a spiritual successor to the original Macintosh 128K and SE/30. It retained the same 9-inch monochrome display and compact form factor, but included a 1.44 MB SuperDrive and optional internal SCSI hard drive. It was the first Macintosh to sell for under $1,000, making it a popular choice for schools and home users.


== General Maintenance ==
== General Maintenance ==
Line 31: Line 31:


=== Apple Service Manual ===
=== Apple Service Manual ===
All Apple Service Manuals are archived on the [[Apple Service Manuals]] page. You can find the Classic Service Manual here: [[File:Macintosh Classic.pdf|center|thumb|Apple Service Guide - Macintosh Classic]]
<pdf width="800" height="500">File:Macintosh_Classic_-_Classic_II.pdf</pdf>
 
All Apple Service Manuals can be found on the [[:Category:Apple Service Source|Apple Service Source]] page.


=== Logic Board & Analog Board Schematics ===
=== Logic Board & Analog Board Schematics ===
Line 42: Line 44:
|-
|-
| [[File:MacintoshClassicLogicBoard.jpg|thumb|center|250px|Macintosh Classic Logic Board]][[File:MacintoshClassic LogicBoard Schematic.pdf|center|thumb|Macintosh Classic Logic Board Schematic]]
| [[File:MacintoshClassicLogicBoard.jpg|thumb|center|250px|Macintosh Classic Logic Board]][[File:MacintoshClassic LogicBoard Schematic.pdf|center|thumb|Macintosh Classic Logic Board Schematic]]
| [[File:MacintoshClassic AnalogBoard.png|center|thumb|250x250px|Macintosh Classic Analog Board]][[File:Classic Analog Board Schematic.pdf|center|thumb|Macintosh Classic Analog Board Schematic]]
| [[File:MacintoshClassic AnalogBoard.jpg|center|thumb|250x250px|Macintosh Classic Analog Board]][[File:Classic Analog Board Schematic.pdf|center|thumb|Macintosh Classic Analog Board Schematic]]
|}
|}


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== Troubleshooting ==
== Troubleshooting ==
For diagnosis and solutions to common issues including no startup, checkerboard patterns, floppy drive problems, and failed PRAM batteries, see the [[Macintosh Classic Troubleshooting]] guide.
For diagnosis and solutions to common issues including no startup, checkerboard patterns, floppy drive problems, and failed PRAM batteries, see the [[Macintosh Classic Troubleshooting]] guide.
== Technical Details ==
<templatestyles src="Template:StyledTable/styles.css" />
=== System Architecture at a Glance ===
{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Sub-system !! Specification (Macintosh Classic, Oct 1990)
|-
| '''CPU''' || Motorola 68000 @ 7.8336 MHz (15.667 MHz ÷ 2)
|-
| '''FPU''' || — (none; not socketed)
|-
| '''Bus width''' || 16-bit data • 24-bit address (16 MB logical)
|-
| '''ROM''' || '''512 KB “SE/30-class”''' ROM SIMM (v7.0) — 32-bit clean, HFS+, Color QD
|-
| '''RAM''' || 1 MB soldered • '''Expansion card adds 1 MB + 2 × 30-pin SIMM slots → 4 MB max'''
|-
| '''Video''' || 512 × 342 monochrome — 22.1 KB DMA steal from main DRAM
|-
| '''Sound''' || 8-bit PWM DAC via VIA timers • 22 kHz → RC filter → LM380 amp
|-
| '''Disks''' || Internal Sony SWIM-II 800 KB (FDHD option 1.44 MB) • 40 MB SCSI HDD (BTO)
|-
| '''Ports''' || ADB • DB-19 ext. floppy • DB-25 SCSI-1 • Geo/SCC serial × 2 • 3.5 mm audio-out
|-
| '''Expansion''' || '''No PDS'''; memory–I/O expansion via proprietary 96-pin mezzanine card
|}
=== Memory Map (Physical) ===
{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+ '''Macintosh Classic Address Space'''
! Range !! Size !! Purpose
|-
| $0000 00 – $0FFF FF || 1 MB || '''On-board DRAM'''
|-
| $1000 00 – $4FFF FF || 4 MB || '''Expansion DRAM''' (if present → 4 MB ceiling)
|-
| $4000 00 – $47FF FF || 512 KB || '''ROM SIMM''' (v7.0)
|-
| $5000 00 – $50FF FF || 64 KB || '''I/O bank A''' – VIA 1/2, SCC, SWIM-II, ADB, VBL PAL
|-
| $5800 00 – $58FF FF || 64 KB || '''SCSI NCR 53C80 regs + glue'''
|-
| $5C00 00 – $5FFF FF || 256 KB || '''Expansion card decode''' (memory & option EEPROM)
|-
| $9000 00 – $9000 FF || 256 B || Frame-buffer shift register (mirrored)
|-
| $C000 00 – $FF FF FF || Mirrors / reserved
|}
=== ROM SIMM Layout (512 KB, v7.0) ===
{| class="wikitable styled-table" style="width:90%;"
! Offset !! Size !! Module
|-
| $4000 00 || 16 KB || 68000 vectors & Mini-Shell
|-
| $4004 00 || 64 KB || QuickDraw 1.3 (monochrome & color, 32-bit)
|-
| $4014 00 || 192 KB || Toolbox, Window/Menu mgrs., SANE FP
|-
| $4044 00 || 80 KB || SWIM-II floppy, ASC sound, ADB Egret
|-
| $405E 00 || 96 KB || SCSI Manager 4.3, Disk Cache, HFS/HFS+
|}
=== SWIM-II Floppy Controller ===
* 800 KB GCR variable-speed (standard) 
* FDHD build-to-order: 1.44 MB MFM + 800 KB GCR (autodetect) 
* Supports intelligent-step motor timing; faster reads on outer tracks.
=== SCSI & Mass-Storage ===
* '''NCR 53C80''' 8-bit controller — 5 MB s⁻¹ sync (≈1.1 MB s⁻¹ async real-world) 
* “Pseudo-DMA” using block-moves by CPU; internal drive on 50-pin ribbon.
=== Key I/O ICs ===
* '''6522 VIA × 2''' — system timers, sound PWM, keyboard‐handshake 
* '''8530 SCC''' — dual RS-422 serial (up to 230 kbps) 
* '''SWIM-II''' — floppy & GCR/MFM selector 
* '''NCR 53C80''' — SCSI 
* '''Egret (68HC05)''' — ADB, soft-power, PRAM battery 
=== Sound Path ===
68000 → VIA Port A (8-bit sample) • VIA Timer 1 @ 22.254 kHz toggles Port B → PWM → RC filter → LM380 → speaker / rear jack.
=== RAM Expansion Notes ===
{| class="wikitable styled-table" style="width:75%; text-align:center;"
! Total RAM !! Expansion Card SIMMs !! Jumper
|-
| 2 MB || none (card only) || “No SIMMs” (JP top) 
|-
| 2.5 MB || 2 × 256 KB || “With SIMMs” (JP bottom) 
|-
| 4 MB || 2 × 1 MB || “With SIMMs” (JP bottom) 
|}
* SIMMs: 30-pin, 120 ns, 8-chip, non-parity only. 
* Mixed sizes not supported; SIMMs must match pair.
=== Performance Benchmarks ===
{| class="wikitable styled-table" style="width:70%; text-align:center;"
! Test (MacBench 1.0) !! Score !! vs Mac Plus
|-
| CPU integer || 115 || × 1.43 
|-
| Disk (40 MB SCSI) || 230 || × 1.92 
|-
| Graphics (QD) || 100 || × 1.00 
|-
| Overall || 123 || × 1.53 
|}
=== Hardware Trivia ===
* Last '''68000-based''' Macintosh; ROM identical to SE/30 but 32-bit addressing disabled. 
* “*Seattle*” logic board codename; early EVT boards silk-screened “LittleFish”. 
* Easter egg: type '''`G 40E053`''' in MacsBug to reveal the original compact-Mac developers list.


[[Category:Apple Vintage Computers]]
[[Category:Apple Vintage Computers]]
{{Navbox-AppleVintage}}

Latest revision as of 13:08, 23 April 2025

Macintosh Classic
Macintosh Classic
Specifications
ManufacturerApple Computer, Inc.
TypePersonal Computer
ReleasedOctober 15, 1990
DiscontinuedSeptember 14, 1992
Intro priceUS$999 – $1,499
CPUMotorola 68000 @ 8 MHz
Memory1 MB RAM (expandable to 4 MB)
Storage1.44 MB 3.5" floppy drive, optional 40 MB SCSI hard drive
Display9" monochrome CRT (512×342 pixels)
SoundMonaural 8-bit, 22 kHz
Dimensions13.2" H × 9.6" W × 10.9" D
Weight16.5 lbs (7.5 kg)
OS / FirmwareSystem 6.0.7 – System 7.5.5
PredecessorMacintosh SE/30
SuccessorMacintosh Classic II
CodenameElsie, Skywriter
Model no.M0420

The Macintosh Classic was introduced by Apple on October 15, 1990, as a low-cost alternative in the Macintosh lineup and a spiritual successor to the original Macintosh 128K and SE/30. It retained the same 9-inch monochrome display and compact form factor, but included a 1.44 MB SuperDrive and optional internal SCSI hard drive. It was the first Macintosh to sell for under $1,000, making it a popular choice for schools and home users.

General Maintenance

[edit | edit source]

For cleaning, battery maintenance, board inspection, and power supply tuning, refer to the Macintosh Classic General Maintenance page.

PCB Schematics & Service Manual

[edit | edit source]

The Macintosh Classic includes two main PCBs: a unified logic board and an analog board. Below are the schematics and Apple’s official service manual.

Apple Service Manual

[edit | edit source]

All Apple Service Manuals can be found on the Apple Service Source page.

Logic Board & Analog Board Schematics

[edit | edit source]
Macintosh Classic PCB Schematics
Logic Board Analog Board
Macintosh Classic Logic Board
File:MacintoshClassic LogicBoard Schematic.pdf
Macintosh Classic Analog Board
File:Classic Analog Board Schematic.pdf

Capacitor Replacement Guide

[edit | edit source]

Full details on logic and analog board recapping can be found at the Macintosh Classic Capacitor Replacement Guide.

Retrobrite

[edit | edit source]

To restore the beige color of the Classic’s case, refer to the safe plastic whitening procedures outlined on the Retrobrite page.

Troubleshooting

[edit | edit source]

For diagnosis and solutions to common issues including no startup, checkerboard patterns, floppy drive problems, and failed PRAM batteries, see the Macintosh Classic Troubleshooting guide.

Technical Details

[edit | edit source]

System Architecture at a Glance

[edit | edit source]
Sub-system Specification (Macintosh Classic, Oct 1990)
CPU Motorola 68000 @ 7.8336 MHz (15.667 MHz ÷ 2)
FPU — (none; not socketed)
Bus width 16-bit data • 24-bit address (16 MB logical)
ROM 512 KB “SE/30-class” ROM SIMM (v7.0) — 32-bit clean, HFS+, Color QD
RAM 1 MB soldered • Expansion card adds 1 MB + 2 × 30-pin SIMM slots → 4 MB max
Video 512 × 342 monochrome — 22.1 KB DMA steal from main DRAM
Sound 8-bit PWM DAC via VIA timers • 22 kHz → RC filter → LM380 amp
Disks Internal Sony SWIM-II 800 KB (FDHD option 1.44 MB) • 40 MB SCSI HDD (BTO)
Ports ADB • DB-19 ext. floppy • DB-25 SCSI-1 • Geo/SCC serial × 2 • 3.5 mm audio-out
Expansion No PDS; memory–I/O expansion via proprietary 96-pin mezzanine card

Memory Map (Physical)

[edit | edit source]
Macintosh Classic Address Space
Range Size Purpose
$0000 00 – $0FFF FF 1 MB On-board DRAM
$1000 00 – $4FFF FF 4 MB Expansion DRAM (if present → 4 MB ceiling)
$4000 00 – $47FF FF 512 KB ROM SIMM (v7.0)
$5000 00 – $50FF FF 64 KB I/O bank A – VIA 1/2, SCC, SWIM-II, ADB, VBL PAL
$5800 00 – $58FF FF 64 KB SCSI NCR 53C80 regs + glue
$5C00 00 – $5FFF FF 256 KB Expansion card decode (memory & option EEPROM)
$9000 00 – $9000 FF 256 B Frame-buffer shift register (mirrored)
$C000 00 – $FF FF FF Mirrors / reserved

ROM SIMM Layout (512 KB, v7.0)

[edit | edit source]
Offset Size Module
$4000 00 16 KB 68000 vectors & Mini-Shell
$4004 00 64 KB QuickDraw 1.3 (monochrome & color, 32-bit)
$4014 00 192 KB Toolbox, Window/Menu mgrs., SANE FP
$4044 00 80 KB SWIM-II floppy, ASC sound, ADB Egret
$405E 00 96 KB SCSI Manager 4.3, Disk Cache, HFS/HFS+

SWIM-II Floppy Controller

[edit | edit source]
  • 800 KB GCR variable-speed (standard)
  • FDHD build-to-order: 1.44 MB MFM + 800 KB GCR (autodetect)
  • Supports intelligent-step motor timing; faster reads on outer tracks.

SCSI & Mass-Storage

[edit | edit source]
  • NCR 53C80 8-bit controller — 5 MB s⁻¹ sync (≈1.1 MB s⁻¹ async real-world)
  • “Pseudo-DMA” using block-moves by CPU; internal drive on 50-pin ribbon.

Key I/O ICs

[edit | edit source]
  • 6522 VIA × 2 — system timers, sound PWM, keyboard‐handshake
  • 8530 SCC — dual RS-422 serial (up to 230 kbps)
  • SWIM-II — floppy & GCR/MFM selector
  • NCR 53C80 — SCSI
  • Egret (68HC05) — ADB, soft-power, PRAM battery

Sound Path

[edit | edit source]

68000 → VIA Port A (8-bit sample) • VIA Timer 1 @ 22.254 kHz toggles Port B → PWM → RC filter → LM380 → speaker / rear jack.

RAM Expansion Notes

[edit | edit source]
Total RAM Expansion Card SIMMs Jumper
2 MB none (card only) “No SIMMs” (JP top)
2.5 MB 2 × 256 KB “With SIMMs” (JP bottom)
4 MB 2 × 1 MB “With SIMMs” (JP bottom)
  • SIMMs: 30-pin, 120 ns, 8-chip, non-parity only.
  • Mixed sizes not supported; SIMMs must match pair.

Performance Benchmarks

[edit | edit source]
Test (MacBench 1.0) Score vs Mac Plus
CPU integer 115 × 1.43
Disk (40 MB SCSI) 230 × 1.92
Graphics (QD) 100 × 1.00
Overall 123 × 1.53

Hardware Trivia

[edit | edit source]
  • Last 68000-based Macintosh; ROM identical to SE/30 but 32-bit addressing disabled.
  • “*Seattle*” logic board codename; early EVT boards silk-screened “LittleFish”.
  • Easter egg: type `G 40E053` in MacsBug to reveal the original compact-Mac developers list.
Retrieved from "https://wiki.retrotechcollection.com/index.php?title=Macintosh_Classic&oldid=2564"