Editing Macintosh LC 520 (section)

== Technical Details ==
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=== System Architecture ===
{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Sub-system !! Specification (Macintosh LC 520, June 1993)
|-
| '''CPU''' || Motorola 68030 @ 25 MHz • 32-bit data bus • 24-bit address (16 MB space)
|-
| '''Bus width''' || 32-bit data • 24-bit address • Full 68030 performance (unlike LC/LC II)
|-
| '''ROM''' || 1 MB ROM (2 × 256K × 16-bit chips) • QuickDraw, ADB, SCSI Manager
|-
| '''RAM''' || 4 MB on-board + 1 MB SIMM standard • '''expandable to 36 MB''' (72-pin SIMM)
|-
| '''Video''' || 512 KB VRAM standard • 640 × 480 at 8-bit color • expandable to 768 KB VRAM
|-
| '''Sound''' || Stereo speakers • Built-in microphone • 8-bit 22.254 kHz sampling
|-
| '''Storage''' || 80 or 160 MB SCSI hard drive • 2× CD-ROM (caddy-loading, 300 KB/s)
|-
| '''I/O Ports''' || ADB × 2 • Mini-DIN-8 serial × 2 • DB-25 SCSI • 3.5mm audio in/out
|-
| '''Expansion''' || Enhanced LC PDS – 114-pin connector, backward compatible with 96-pin cards
|}

=== Memory Configuration ===
{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''RAM Expansion Options'''
! Configuration !! On-board !! SIMM Size !! Total RAM
|-
| Minimum || 4 MB || None || 4 MB
|-
| Standard || 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
|}

'''SIMM Requirements:''' 72-pin, 80ns or faster, supports 1, 2, 4, 8, 16, or 32 MB modules

=== Video Specifications ===
{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''Display Capabilities'''
! VRAM !! Resolution !! Color Depth !! Colors
|-
| 512 KB || 640 × 480 || 8-bit || 256 colors
|-
| 768 KB || 640 × 480 || 16-bit || Thousands of colors
|-
| 512 KB || 560 × 384 || 4-bit || 16 colors (Apple IIe Card mode)
|}

The 14-inch Sony Trinitron CRT provides:
* 0.26mm dot pitch
* Maximum 640 × 480 resolution
* 60 Hz refresh rate
* Integrated degaussing coil

=== Enhanced LC PDS Specifications ===

The LC 520 introduced the enhanced LC PDS slot with 114 pins, maintaining backward compatibility with 96-pin cards from earlier LC models.

'''Compatible expansion cards:'''
* '''Apple IIe Card''' – Apple II emulation with Y-cable for 5.25" drive support
* '''Ethernet cards''' – Various 10BASE-T and AAUI options from Apple, Asante, Farallon
* '''Video cards''' – External monitor support (rare)
* '''Accelerator cards''' – DayStar PowerCache upgrades

'''PDS Technical Details:'''
* Direct connection to 68030 processor bus
* 25 MHz synchronous operation
* 32-bit data path (16-bit compatible mode for older cards)
* Three interrupt lines (IPL0-IPL2)
* +5V and +12V power available

=== FPU Compatibility ===

The LC 520 includes an empty socket for a Motorola 68882 FPU operating at 25 MHz. Installation considerations:
* FPU socket on motherboard can be populated with 68882
* Some PDS Ethernet cards include FPU sockets
* Running FPU on both motherboard and PDS card simultaneously is not recommended
* FPU provides significant acceleration for scientific and graphics applications

=== Storage Subsystem ===

==== SCSI Hard Drive ====
* '''Interface:''' 50-pin internal SCSI-1
* '''Controller:''' NCR 5380 or compatible
* '''Transfer rate:''' Up to 5 MB/s (asynchronous)
* '''Capacities:''' 80 MB or 160 MB standard configurations
* '''Common drives:''' Quantum ProDrive LPS, Connor CP30084

==== CD-ROM Drive ====
* '''Speed:''' 2× (300 KB/s)
* '''Type:''' Caddy-loading mechanism
* '''Interface:''' Internal SCSI (ID 3 typical)
* '''Format support:''' ISO 9660, HFS, Audio CD, Photo CD (with software)
* '''Mechanism:''' Sony CDU-541 or compatible

==== Floppy Drive ====
* '''Type:''' Sony MPF-75W SuperDrive
* '''Capacity:''' 1.44 MB high-density, 800 KB double-density, 400 KB single-density
* '''Controller:''' SWIM chip
* '''Location:''' Front-loading, manual inject

=== Audio System ===

The LC 520 featured enhanced audio capabilities compared to pizza-box LC models:
* '''Stereo speakers''' integrated into case sides
* '''Built-in microphone''' (omnidirectional electret)
* '''Sound input:''' 22.254 kHz sampling, 8-bit
* '''Sound output:''' Stereo, 8-bit DAC
* '''Audio ports:''' 3.5mm stereo output, 3.5mm mono input

=== Power Specifications ===
* '''Input:''' 100-240V AC, 50-60 Hz (auto-switching)
* '''Power consumption:''' 150W typical, 200W maximum
* '''Internal voltages:''' +5V (logic), +12V (drives), -12V (serial), high voltage for CRT