Macintosh 512Ke
 | |
| Specifications | |
|---|---|
| Manufacturer | Apple Computer, Inc. |
| Type | Personal Computer |
| Released | April 14, 1986 |
| Discontinued | September 1, 1987 |
| Intro 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 / Firmware | System 1.0 – System 6.0.8 |
| Predecessor | Macintosh 512K |
| Successor | Macintosh Plus |
| Codename | M0001E |
| Model no. | 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
[edit | edit source]- 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
[edit | edit source]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
[edit | edit source]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
[edit | edit source]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
[edit | edit source]System Architecture at a Glance
[edit | edit source]| 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
|
| 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)
[edit | edit source]| 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)
[edit | edit source]| 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
[edit | edit source]- 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
[edit | edit source]- 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
[edit | edit source]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
[edit | edit source]- 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
[edit | edit source]Hold ⌘ + Option + ⇧ + Clear at power-on for the hidden bass “startup” chime—retained from earlier ROMs.