Editing Macintosh 512Ke

{{Infobox computer
| name         = Macintosh 512Ke
| image        = [[File:Macintosh128K.jpg|250px]]
| manufacturer = Apple Computer, Inc.
| type         = Personal Computer
| release_date = April 14, 1986
| discontinued = September 1, 1987
| price        = US$1,999
| cpu          = Motorola 68000 @ 7.83 MHz
| memory       = 512 KB RAM (built‑in)
| storage      = 800 KB 3.5″ floppy drive
| display      = 9″ monochrome CRT (512×342)
| sound        = Monaural, 8‑bit
| dimensions   = 13.6″ H × 9.6″ W × 10.9″ D
| weight       = 16.5 lbs (7.5 kg)
| os           = System 1.0 – System 6.0.8
| predecessor  = [[Macintosh 512K]]
| successor    = [[Macintosh Plus]]
| codename     = M0001E
| model        = M0001E
}}
The '''Macintosh 512Ke''' (often called the 512K “enhanced”) was introduced by Apple on April 14, 1986, as a cost‑effective alternative to the Macintosh Plus. It combined the 512 KB RAM and compact case of the [[Macintosh 512K]] with the 800 KB floppy drive and 128 KB ROM of the Macintosh Plus, unlocking support for newer System software and utilities.

== Features ==
* '''800 KB Floppy Drive''' – Double‑sided drive offering twice the native disk capacity of earlier models.  
* '''128 KB ROM from Mac Plus''' – Built‑in SCSI Manager support (no physical SCSI port), enabling compatibility with SCSI‑based hard drives via third‑party adapters.  
* '''Educational Edition''' – Late‑life rebadged as the “Macintosh ED” for schools, with identical hardware but educational packaging.  
* '''Limited Expansion''' – No internal slots; RAM upgrades and SCSI adapters were supplied by third parties, often boosting memory to 2 MB+.

== System Software ==
Shipped with System 3.2; later officially supported up to System 6.0.8. In practice, many users ran System 5.x for a balance of features and available memory.

== Upgrade Paths ==
Official Apple upgrade kit (US $299) for the 512Ke included:
# 800 KB floppy drive  
# 128 KB ROM chips  
# Macintosh Plus System Tools disk and installation guide  

Third‑party kits offered SCSI port cards and RAM expansions (up to 2 MB or more), addressing the machine’s expansion limitations.

== Maintenance ==
The 512Ke shares its PCB layout and servicing procedures with the [[Macintosh 128K]] and [[Macintosh 512K]]. For cleaning, capacitor replacement guides, and general servicing, see [[Macintosh 128K/512K General Maintenance]].

== Technical Details ==
<templatestyles src="Template:StyledTable/styles.css" />

=== System Architecture at a Glance ===
{| class="wikitable styled-table" style="width:70%; text-align:center;"
! Sub-system !! Specification (Macintosh 512Ke, 1986)
|-
| '''CPU''' || Motorola 68000 @ 7.8336 MHz   (15.667 MHz ÷ 2)  
|-
| '''Bus width''' || 16-bit data • 24-bit address  (16 MB logical)  
|-
| '''ROM''' || '''128 KB “Plus-class”''' ROM  
*(Twice the 64 KB of the 512 K / 128 K; adds HFS, SCSI Manager, 800 K disk routines)*  
|-
| '''RAM''' || 512 KB DRAM  (16 × 256-Kbit 150 ns) – *soldered*  
|-
| '''Video''' || 512 × 342 monochrome frame-buffer (22.1 KB) DMA-shared with RAM  
|-
| '''Sound''' || 8-bit PWM DAC via VIA timers • 22 kHz RC filter → LM380 amp  
|-
| '''Disk I/O''' || '''Sony OA-D34V-22 800 KB''' auto-inject 3.5″ drive • IWM controller  
|-
| '''Ports''' || DE-9 mouse/KB • DB-19 ext. floppy • RS-422 serial × 2 (230 kbps) • 3.5 mm audio-out  
|}

=== Memory Map (Physical) ===
{| class="wikitable styled-table" style="width:70%; text-align:center;"
|+'''Macintosh 512Ke Address Space'''
! Range !! Size !! Purpose
|-
| $000000 – $07FFFF || 512 KB || '''DRAM''' (program, heap, frame-buffer)
|-
| $400000 – $41FFFF || 128 KB || '''ROM''' (v3.4 “Plus” Toolbox)  
|-
| $480000 – $4BFFFF || 256 KB || '''I/O''' (VIA 1/2, SCC, IWM, VBL PAL)
|-
| $500000 – $5FFFFF || 1 MB || '''Reserved / not decoded'''
|-
| $600000 – $FFFFFF || Mirrors / ghost ranges
|}

*Frame-buffer note:* 22 016-byte display buffer lives at '''$07B000 – $07FFFF'''.

=== ROM Layout (v3.4 128 KB set) ===
{| class="wikitable styled-table" style="width:80%;"
! Offset !! Size !! Module
|-
| $400000 || 8 KB || 68000 vectors + Mini-Shell
|-
| $402000 || 20 KB || QuickDraw 1.1  (mono, patched)
|-
| $407000 || 52 KB || Toolbox, SANE, Mouse & Keyboard drivers
|-
| $414000 || 24 KB || Sony 800 KB IWM driver, HFS routines
|-
| $41A000 || 24 KB || SCSI Manager, Disk Cache, I/O traps
|}

=== 800 KB Floppy Format ===
* 80 tracks • '''double-sided''' • variable-speed GCR  
* 12 → 8 sectors/track (outer→inner) • 512-byte sectors  
* 800 KB formatted • still driven by IWM (no SWIM yet) with ROM-based speed tables

=== Key I/O ICs ===
* '''6522 VIA × 2''' — timers, sound PWM, keyboard/mouse handshake  
* '''8530 SCC''' — dual RS-422 serial  
* '''IWM''' — Integrated Woz Machine floppy controller  
* '''MC6883 PAL''' — VBL interrupt & DRAM arbitration

=== Sound Path ===
68000 → VIA Port A (8-bit sample) • VIA Timer 1 toggles Port B @ 22.254 kHz → PWM → RC filter → LM380 amp → speaker/headphones.

=== ROM Enhancements vs. 512 K ===
* '''HFS file system''' support (400 KB disks can be HFS-formatted).  
* '''SCSI Manager''' present (unused until external SCSI upgrade boards).  
* '''“Backwards-compatible”''': still boots MFS and runs 128 K/512 K apps.

=== Hardware Easter Egg ===
Hold '''⌘ + Option + ⇧ + Clear''' at power-on for the hidden bass “startup” chime—retained from earlier ROMs.


[[Category:Apple Vintage Computers]]
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