Editing Macintosh Plus (section)

== Technical Details ==

=== Processor Specifications ===
{| class="wikitable styled-table"
|-
! Component !! Specification
|-
| CPU || Motorola 68000 @ 8 MHz<ref>{{cite web |url=https://everymac.com/systems/apple/mac_classic/specs/mac_plus.html |title=Macintosh Plus (ED) Specs |publisher=EveryMac.com |date=1996 |access-date=2025-05-26}}</ref>
|-
| Data Bus || 16-bit<ref>{{cite web |url=https://lowendmac.com/2014/cpus-motorola-68000/ |title=CPUs: Motorola 68000 |publisher=Low End Mac |date=2014-06-14 |access-date=2025-05-26}}</ref>
|-
| Address Bus || 24-bit<ref>{{cite web |url=https://lowendmac.com/2014/cpus-motorola-68000/ |title=CPUs: Motorola 68000 |publisher=Low End Mac |date=2014-06-14 |access-date=2025-05-26}}</ref>
|-
| Internal Registers || 32-bit<ref>{{cite web |url=https://lowendmac.com/2014/cpus-motorola-68000/ |title=CPUs: Motorola 68000 |publisher=Low End Mac |date=2014-06-14 |access-date=2025-05-26}}</ref>
|-
| Performance || 0.7 MIPS<ref>{{cite web |url=https://lowendmac.com/1986/mac-plus/ |title=Mac Plus |publisher=Low End Mac |date=1986-01-16 |access-date=2025-05-26}}</ref>
|}

=== Memory Configuration ===
{| class="wikitable styled-table"
|-
! Type !! Specification
|-
| Standard RAM || 1 MB<ref>{{cite web |url=https://en.wikipedia.org/wiki/Macintosh_Plus |title=Macintosh Plus |publisher=Wikipedia |date=2025-04-28 |access-date=2025-05-26}}</ref>
|-
| Maximum RAM || 4 MB<ref>{{cite web |url=https://en.wikipedia.org/wiki/Macintosh_Plus |title=Macintosh Plus |publisher=Wikipedia |date=2025-04-28 |access-date=2025-05-26}}</ref>
|-
| SIMM Slots || 4 × 30-pin<ref>{{cite web |url=https://en.wikipedia.org/wiki/Macintosh_Plus |title=Macintosh Plus |publisher=Wikipedia |date=2025-04-28 |access-date=2025-05-26}}</ref>
|-
| SIMM Speed || 150ns<ref>{{cite web |url=https://lowendmac.com/1986/mac-plus/ |title=Mac Plus |publisher=Low End Mac |date=1986-01-16 |access-date=2025-05-26}}</ref>
|-
| ROM || 128 KB<ref>{{cite web |url=https://en.wikipedia.org/wiki/Macintosh_Plus |title=Macintosh Plus |publisher=Wikipedia |date=2025-04-28 |access-date=2025-05-26}}</ref>
|}

=== Physical Specifications ===
{| class="wikitable styled-table"
|-
! Dimension !! Measurement
|-
| Height || 13.6" (34.5 cm)<ref>{{cite web |url=https://www.dimensions.com/element/apple-macintosh-128k-1984 |title=Apple Macintosh 128K (1984) Dimensions |publisher=Dimensions.com |date=2024 |access-date=2025-05-26}}</ref>
|-
| Width || 9.6" (24.4 cm)<ref>{{cite web |url=https://www.dimensions.com/element/apple-macintosh-128k-1984 |title=Apple Macintosh 128K (1984) Dimensions |publisher=Dimensions.com |date=2024 |access-date=2025-05-26}}</ref>
|-
| Depth || 10.9" (27.7 cm)<ref>{{cite web |url=https://www.dimensions.com/element/apple-macintosh-128k-1984 |title=Apple Macintosh 128K (1984) Dimensions |publisher=Dimensions.com |date=2024 |access-date=2025-05-26}}</ref>
|-
| Weight || 16.5 lb (7.5 kg)<ref>{{cite web |url=https://lowendmac.com/1986/mac-plus/ |title=Mac Plus |publisher=Low End Mac |date=1986-01-16 |access-date=2025-05-26}}</ref>
|-
| Power Consumption || 60 watts maximum<ref>{{cite web |url=https://support.apple.com/kb/SP190 |title=Macintosh Plus: Technical Specifications |publisher=Apple Support |date=1986 |access-date=2025-05-26}}</ref>
|}

=== ROM Layout (128 KB, v4.0 "Plus-class") ===
{| class="wikitable styled-table" style="width:80%;"
! Offset !! Size !! Module
|-
| $400000 || 8 KB || 68000 vectors + Mini-Shell
|-
| $402000 || 20 KB || QuickDraw 1.2 (monochrome, relocatable)
|-
| $407000 || 52 KB || Toolbox, SANE, Font & Menu mgrs.
|-
| $414000 || 16 KB || Sony 800 KB floppy driver & IWM tables
|-
| $418000 || 24 KB || SCSI Manager, Disk Cache, HFS
|-
| $41E000 || 8 KB || I/O traps, Declarations, Copyright
|}

=== SCSI Sub-system ===
* Western Digital '''WD 5380''' NCR-compatible controller
* 5 MB s⁻¹ 8-bit synchronous (practically 1.2 MB s⁻¹ async)  
* DMA-like handshake handled in software by 68000 — no true DMA

=== Floppy-Disk Format (800 KB GCR) ===
* 80 tracks • double-sided variable-speed  
* 12 → 8 sectors/track (outer→inner) • 512-byte sectors  
* 800 KB formatted • still uses IWM (not yet SWIM)

=== Key I/O ICs ===
* '''6522 VIA × 2''' — timers, sound PWM, keyboard/mouse 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''' — dual RS-422 serial (230 kbps)  
* '''IWM''' — Integrated Woz Machine floppy controller  
* '''WD 5380''' — 8-bit SCSI controller  
* '''MC6883 PAL''' — VBL interrupt & DRAM cycle arbiter

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

=== RAM Upgrade Notes ===
* Uses four 30-pin SIMM sockets (Bank 0 & Bank 1).  
* Accepts 256 KB or 1 MB SIMMs, 150 ns or faster.  
* Mixed sizes allowed per bank (must match within a bank); 4 MB max.

=== Hardware Easter Egg ===
Boot while holding '''⌘ + Option + ⇧ + Clear''' to hear the hidden *bass-only* startup chime — final compact-Mac model to include it.<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>