Editing Macintosh Classic II (section)

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

=== System Architecture at a Glance ===
{| class="wikitable styled-table" style="width:95%; text-align:center;"
! Sub-system !! Specification (Macintosh Classic II / Performa 200, Oct 1991)
|-
| '''CPU''' || Motorola 68030 @ 16.67 MHz (33.33 MHz ÷ 2)
Internal 32-bit core on a '''16-bit external data bus'''
|-
| '''FPU''' || — (none; 68882 socket removed to cut cost)
|-
| '''Chipset''' || '''“V8 Lite”''' ASIC (MEMCjr + I/O GLU) handles DRAM, video DMA, VIA timers  
|-
| '''ROM''' || '''512 KB “IIci-class”''' ROM SIMM (v7.1) — Color QD 1.3, 32-bit clean, SCSI Mgr 4.3
|-
| '''RAM (base)''' || 2 MB soldered (8 × 256 K × 4 DRAM, 100 ns)
|-
| '''RAM (slots)''' || 2 × 30-pin SIMM — accepts 256 KB, 1 MB, 4 MB (80 ns)  
'''Max = 10 MB''' (2 MB on-board + 2 × 4 MB)
|-
| '''Video''' || 512 × 342 mono (22.1 KB) DMA-steals from main DRAM  
VRAM “page” is dual-ported inside MEMCjr
|-
| '''Sound''' || 8-bit PWM DAC via VIA Timer-1 • 22 kHz → RC filter → LM380 amp
|-
| '''Storage''' || Internal Apple FDHD 1.44 MB (SWIM-II) • 40–160 MB 2.5″ SCSI HDD
|-
| '''Ports''' || ADB • DB-19 ext floppy • DB-25 SCSI-1 • RS-422 serial × 2 • 3.5 mm audio-out
|-
| '''Expansion''' || '''No PDS'''; logic-board edge exposes debug pads only.
|}

=== Physical Memory Map ===
{| class="wikitable styled-table" style="width:85%; text-align:center;"
|+ '''Classic II Address Space'''
! Range (hex) !! Size !! Purpose
|-
| $0000 00 – $1FFF FF || 2 MB || '''On-board DRAM''' (base memory)
|-
| $2000 00 – $9FFF FF || 8 MB || '''SIMM DRAM banks''' (if present)
|-
| $4000 00 – $47FF FF || 512 KB || '''ROM SIMM''' (v7.1)
|-
| $5000 00 – $50FF FF || 64 KB || '''I/O Bank A''' — VIA-1/2, SCC, SWIM-II, V8 Lite, Egret
|-
| $5800 00 – $58FF FF || 64 KB || '''NCR 53C96 SCSI''' + glue
|-
| $5C00 00 – $5FFF FF || 256 KB || '''Unused / test decode'''
|-
| $9000 00 – $9000 FF || 256 B || '''Video shift register''' (mirrored)
|-
| $C000 00 – $FF FF FF || Mirror / reserved
|}

*Frame-buffer:* 22,016-byte screen bitmap sits at top of total DRAM (e.g. $9FE000–$9FFFFF in a 10 MB system).

=== ROM SIMM Breakdown (512 KB, v7.1) ===
{| class="wikitable styled-table" style="width:90%;"
! Offset !! Size !! Module
|-
| $4000 00 || 16 KB || 68030 vectors + micro-shell
|-
| $4004 00 || 64 KB || Color / Mono QuickDraw 1.3 (32-bit)
|-
| $4014 00 || 192 KB || Toolbox, Window/Menu mgrs., SANE FP
|-
| $4044 00 || 80 KB || SWIM-II, ASC 8-bit audio, Egret ADB
|-
| $405E 00 || 96 KB || SCSI Mgr 4.3, Disk Cache, HFS/HFS+
|}

=== Key Silicon & I/O Devices ===
* '''MEMCjr / V8 Lite ASIC''' — DRAM controller, 68030 bus mux, video DMA, VIA handshake  
* '''6522 VIA × 2''' — timers, sound PWM, keyboard latch  
* '''8530 SCC''' — dual RS-422 serial (GeoPort ready)  
* '''SWIM-II''' — GCR/MFM floppy (800 KB & 1.44 MB)  
* '''NCR 53C96''' — fast SCSI, 8-bit DMA style  
* '''Egret 68HC05''' — ADB host, PRAM, soft-power, real-time clock

=== DRAM & SIMM Configuration ===
{| class="wikitable styled-table" style="width:70%; text-align:center;"
! Total RAM !! On-board !! SIMM 1 !! SIMM 2 !! Notes
|-
| 2 MB || 2 MB || — || — || Base model
|-
| 4 MB || 2 MB || 1 MB || 1 MB || SIMMs must match size/speed
|-
| 6 MB || 2 MB || 2 MB || 2 MB || (rare)
|-
| 8 MB || 2 MB || 3 MB* || 3 MB* || *3 MB = 1 MB + 2 MB parity boards
|-
| 10 MB || 2 MB || 4 MB || 4 MB || Official maximum
|}
SIMM requirements:*

30-pin, 80 ns, 8-chip, non-parity (parity ignored).  
Logic board auto-detects via address-pin strapping; no jumpers.

=== Video Timing ===
{| class="wikitable styled-table" style="width:65%; text-align:center;"
! Parameter !! Value
|-
| Pixel clock || 15.667 MHz (÷ 1)
|-
| Horizontal total || 704 px (512 active)
|-
| Vertical total || 370 lines (342 active)
|-
| Refresh rate || 60.15 Hz
|}

==== Performance Snapshot (MacBench 1.0) ====
{| class="wikitable styled-table" style="width:70%; text-align:center;"
! Test !! Score !! vs SE/30
|-
| CPU integer || 135 || 0.47×  
|-
| Disk (80 MB) || 240 || 0.20×  
|-
| Graphics || 110 || 0.45×  
|-
| Overall || 128 || 0.50×  
|}

''Classic II halves the SE/30’s performance despite sharing a 68030, due to the 16-bit data path, slower DRAM, and “pseudo-DMA” SCSI.''

=== Notable Design Traits & Trivia ===
* Marketed as '''Performa 200''' (consumer bundle) in some regions.  
* Last all-in-one Macintosh to support '''32-bit clean ROM''' but ships with '''24-bit addressing forced'''; Mode32 enabler restores full 32-bit memory access.  
* “'''Paris'''” logic-board codename; PCB bears Eiffel-Tower silkscreen.  
* Developer jumper JP3 forces Debug-ROM shell on cold boot for board-level diagnostics.  
* Hidden ROM tone: press '''⌘ + ⌥ + ⌫ + Power''' to trigger a harmonic “strum” on cold start.

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