Editing Macintosh LC 630 (section)

== Technical Details ==
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=== System Architecture ===
{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Sub-system !! Specification (Macintosh LC 630, July 1994)
|-
| '''CPU''' || Motorola 68LC040 @ 33 MHz • No FPU (Quadra 630 has full 68040)
|-
| '''Bus width''' || 32-bit data • 32-bit address (4 GB addressable space)
|-
| '''ROM''' || 1 MB ROM • System 7.1+ support • IDE driver support
|-
| '''RAM''' || 4 MB soldered • '''expandable to 36 MB''' standard (68 MB with modification)
|-
| '''Video''' || 1 MB DRAM (not VRAM) • 640 × 480 at 16-bit • 832 × 624 at 8-bit
|-
| '''Sound''' || Stereo 16-bit sound • 44.1 kHz sampling • Front headphone jack
|-
| '''Storage''' || 250-500 MB IDE hard drive • Optional 2X CD-ROM (SCSI)
|-
| '''I/O Ports''' || ADB × 2 • Mini-DIN-8 serial × 2 • DB-25 SCSI • Audio in/out
|-
| '''Expansion''' || Extended LC PDS • Comm Slot • Video input slot
|}

=== Memory Configuration ===

The LC 630 memory system varies by model, with some featuring a single SIMM slot and others (DOS Compatible, Performa 631/640) having two:

{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''Single SIMM Slot Models'''
! Configuration !! Soldered !! SIMM Slot 1 !! Total RAM
|-
| Minimum || 4 MB || Empty || 4 MB
|-
| || 4 MB || 1 MB || 5 MB
|-
| || 4 MB || 2 MB || 6 MB
|-
| || 4 MB || 4 MB || 8 MB
|-
| || 4 MB || 8 MB || 12 MB
|-
| || 4 MB || 16 MB || 20 MB
|-
| Maximum || 4 MB || 32 MB || 36 MB
|-
| With 64 MB SIMM* || 4 MB || 64 MB || 68 MB
|-
| Reported 128 MB** || 4 MB || 128 MB || 132 MB
|}

''*Single-banked 64 MB SIMMs only; double-banked not supported''
''**Unofficial; one user reported stable operation with 128 MB SIMM''

{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''Dual SIMM Slot Models (DOS Compatible/631/640)'''
! Configuration !! Soldered !! Slot 1 !! Slot 2*** !! Total RAM
|-
| Minimum || 4 MB || Empty || Empty || 4 MB
|-
| Standard DOS || 4 MB || 4 MB || Empty || 8 MB
|-
| || 4 MB || 32 MB || Empty || 36 MB
|-
| || 4 MB || 32 MB || 1 MB || 37 MB
|-
| || 4 MB || 32 MB || 4 MB || 40 MB
|-
| Maximum || 4 MB || 32 MB || 16 MB || 52 MB
|}

''***Slot 2 accepts only single-sided SIMMs (1, 4, or 16 MB)''

'''SIMM Specifications:'''
* 72-pin, 80ns or faster
* Non-parity (parity ignored if present)
* 2K refresh rate or better
* Standard sizes: 1, 2, 4, 8, 16, 32 MB

=== Second SIMM Slot Modification ===

Single-slot LC 630 boards include unpopulated solder pads for a second SIMM socket. Users can solder a 72-pin socket to these pads, enabling dual-slot functionality:
* Increases maximum RAM from 36 MB to 52 MB
* Second slot limited to single-sided SIMMs (16 MB maximum)
* Requires basic soldering skills
* Socket sourced from PC motherboards or electronics suppliers

=== IDE Storage Subsystem ===

The LC 630 was the first desktop Mac with IDE storage:

'''IDE Controller Specifications:'''
* '''Single device support only''' (no master/slave)
* '''PIO Mode 3 maximum''' (11.1 MB/s theoretical)
* '''8 GB addressing limit''' (controller limitation)
* '''No SCSI termination power''' (relies on external devices)

'''Common Issues:'''
* System 7.5.1 and earlier cannot recognize modern IDE drives
* Requires Drive Setup 1.0.3+ or third-party utilities
* Some drives require manufacturer-specific formatting tools

'''CD-ROM (when present):'''
* Apple CD 300i Plus (2X speed, SCSI)
* Tray-loading mechanism (replaced Quadra 610's caddy system)
* Reads 656 MB and 748 MB data CDs
* Audio CD playback support

=== Video System ===

The LC 630 uses shared DRAM instead of dedicated VRAM:

'''Video Memory Architecture:'''
* 1 MB DRAM soldered to motherboard
* Shared with system operations (causes performance penalty)
* Cannot be upgraded
* Results in screen flicker potential

'''Display Capabilities:'''
{| class="wikitable styled-table" style="width:70%; text-align:center;"
! Resolution !! Color Depth !! Colors !! Notes
|-
| 512 × 384 || 16-bit || 32,768 || Standard 12" RGB
|-
| 640 × 480 || 16-bit || 32,768 || VGA/13" RGB
|-
| 832 × 624 || 8-bit || 256 || 16" monitor
|-
| 1024 × 768 || 4-bit || 16 || Requires 19" monitor
|}

MacWorld testing described video performance as "mediocre" due to DRAM sharing and lack of acceleration.

=== Expansion Architecture ===

The LC 630 features three distinct expansion slots:

==== Extended LC PDS ====
* '''114-pin connector''' (backward compatible with 96-pin LC cards)
* Supports both LC II (96-pin) and LC III/520 (114-pin) cards
* Direct 68040 bus access at 33 MHz
* Used by DOS Compatibility Card (occupies CPU socket and PDS)

==== Communication Slot ====
* Original Comm Slot standard (not Comm Slot II)
* Based on LC PDS architecture
* Supports modems and 10BASE-T Ethernet
* Modem installation disables external modem port

==== Video Input Slot ====
* Unique to 630 and LC 580 series
* Supports Apple Video System Card
* Enables TV tuner functionality (Performa 637CD/638CD)
* Allows video capture and overlay

=== DOS Compatibility Card ===

The LC 630 DOS Compatible features a unique dual-processor architecture:

'''DOS Card Specifications:'''
* '''Processor:''' Intel 486DX2/66 MHz or Cyrix 486DX2/66 (some models)
* '''RAM:''' Up to 32 MB dedicated (separate SIMM slot on card)
* '''Connectivity:''' Occupies CPU socket and PDS slot simultaneously
* '''Unique feature:''' PC game port for joystick support
* '''Video:''' Shares Mac video output (no hydra cable required)
* '''Software:''' MS-DOS 6.22, Windows 3.1, SoundBlaster drivers

'''DOS Card Architecture:'''
* Card consists of two PCBs connected together
* Lower board plugs into 68LC040 socket
* Upper board connects to PDS slot
* Leaves Comm Slot and video slot available
* Can share Mac RAM or use dedicated RAM

'''CPU Upgrade Potential:'''
* Socket supports 5V processors with 33 MHz bus
* Successful upgrades: Cyrix 5x86-100GP
* AMD 5x86-133 and Intel DX4-100 cause Windows 95 instability
* Requires voltage adapter for 3.3V processors

=== Custom Chips & Controllers ===
{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Chip !! Function !! Details
|-
| '''68LC040''' || Main CPU || 33 MHz, no FPU (field-upgradeable to 68040)
|-
| '''SWIM II''' || Floppy controller || 400K, 800K, 1.44 MB disk support
|-
| '''NCR 53C96''' || SCSI controller || CD-ROM and external devices only
|-
| '''IDE controller''' || Hard drive interface || Integrated, single device support
|-
| '''CUDA''' || ADB/Power || Handles ADB, power control, PRAM
|-
| '''AWACS''' || Audio || 16-bit stereo sound generation
|}

=== Case Design Innovation ===

The LC 630 introduced several design firsts:

'''Front Panel Features:'''
* Volume up/down buttons (first for Macintosh)
* 3.5mm headphone jack
* Infrared receiver for TV remote (637CD/638CD models)
* Activity LEDs for power and drive access

'''Slide-Out Motherboard:'''
* Rear panel opens downward
* Logic board mounted on sliding drawer
* No tools required for RAM/expansion access
* Similar mechanism later used in LC 575/580

'''Thermal Design:'''
* Passive cooling (no system fan)
* Ventilation slots on top and sides
* Heat sink on 68040 processor
* DOS card includes additional heat sink

=== PowerPC Upgrade Path ===

Apple Macintosh Processor Upgrade Card:
* PowerPC 601 at 50 MHz (Apple) or 100 MHz (third-party)
* Installs in LC PDS slot
* Enables Mac OS 8.5-9.1 support
* Maintains 68040 emulation

Third-party options:
* DayStar PowerCache accelerators
* Sonnet Presto PPC upgrades
* Various clock-chipping modifications

=== Overclock Potential ===

The LC 630 supports a 40 MHz overclock modification:
* Remove specific resistors on logic board
* Increases CPU from 33 MHz to 40 MHz
* 21% performance improvement
* DOS card (if installed) maintains 66 MHz operation
* Procedure identical to Performa 580 modification