Editing Macintosh LC 580 (section)

== Technical Details ==
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=== System Architecture ===
{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Sub-system !! Specification (Macintosh LC 580, April 1995)
|-
| '''CPU''' || Motorola 68LC040 @ 33 MHz • No FPU (upgradeable to 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 on-board (1 MB used for VRAM) • '''expandable to 52 MB''' via dual SIMMs
|-
| '''Video''' || 1 MB shared system RAM • 640 × 480 at 16-bit color maximum
|-
| '''Sound''' || Stereo 16-bit sound • 44.1 kHz sampling • Built-in stereo speakers
|-
| '''Storage''' || 500 MB IDE hard drive • 2X or 4X CD-ROM (SCSI) • 1.44 MB floppy
|-
| '''I/O Ports''' || ADB × 2 • Mini-DIN-8 serial × 2 • DB-25 SCSI • Audio in/out
|-
| '''Expansion''' || LC PDS • Comm Slot • Video input slot (LC 630-compatible)
|}

=== Memory Configuration ===

The LC 580 features an unusual asymmetric dual-SIMM configuration inherited from the LC 630:

{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''RAM Expansion Options'''
! Configuration !! On-board !! SIMM Slot 1 !! SIMM Slot 2 !! Total RAM !! Notes
|-
| Minimum || 4 MB || Empty || Empty || 4 MB || 1 MB used for video
|-
| Standard || 4 MB || 4 MB || Empty || 8 MB || Factory configuration
|-
| || 4 MB || 8 MB || Empty || 12 MB || 
|-
| || 4 MB || 16 MB || Empty || 20 MB ||
|-
| || 4 MB || 32 MB || Empty || 36 MB || Slot 1 maximum
|-
| || 4 MB || 32 MB || 1 MB || 37 MB || Slot 2 limited options
|-
| || 4 MB || 32 MB || 4 MB || 40 MB ||
|-
| Maximum || 4 MB || 32 MB || 16 MB || 52 MB || Unusual limit
|}

'''SIMM Slot Limitations:'''
* '''Slot 1:''' Accepts 1, 2, 4, 8, 16, or 32 MB SIMMs (full range)
* '''Slot 2:''' Accepts only 1, 4, or 16 MB SIMMs (restricted)
* 72-pin, 80ns or faster required
* Single-banked 64 MB SIMMs work in Slot 1 only
* Double-banked 64 MB SIMMs not supported

=== Display Specifications ===

The LC 580 replaced the LC 575's Sony Trinitron with a cheaper shadow mask CRT:

{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''Shadow Mask vs Trinitron Comparison'''
! Feature !! LC 580 (Shadow Mask) !! LC 575 (Trinitron)
|-
| '''Technology''' || Shadow mask with triangular phosphor triads || Aperture grille with vertical phosphor stripes
|-
| '''Brightness''' || Lower (mask blocks more electrons) || Higher (grille more efficient)
|-
| '''Color saturation''' || Good || Superior
|-
| '''Sharpness''' || Good text clarity || Slightly softer text
|-
| '''Artifacts''' || None || Two horizontal stabilization wires visible
|-
| '''Cost''' || Lower || Higher
|-
| '''Dot pitch''' || 0.28mm || 0.26mm aperture grille
|}

'''Display Capabilities:'''
* 640 × 480 at 256 colors (8-bit)
* 640 × 480 at thousands of colors (16-bit) 
* 560 × 384 at 16 colors (Apple IIe Card mode)
* 60 Hz refresh rate
* 14" diagonal viewable area

The plastic bezel was slightly modified to accommodate the different CRT tube depth.

=== IDE Storage Subsystem ===

The LC 580 was the first LC 500 series Mac with IDE storage:

'''IDE Controller Specifications:'''
* '''Interface:''' Single-device IDE (no slave support)
* '''PIO Mode:''' Mode 3 maximum (11.1 MB/s theoretical)
* '''Common drives:''' Western Digital Caviar, Quantum ProDrive
* '''Capacities:''' 250 MB or 500 MB standard

'''IDE Compatibility Issues:'''
* Early versions of Apple HD SC Setup (System 7.5.1 and earlier) cannot recognize modern IDE drives
* Requires Drive Setup 1.0.3 or later (System 7.5.2+) for proper formatting
* Some third-party drives require manufacturer-specific utilities

=== Video Input Capabilities ===

The LC 580 introduced a video input slot compatible with LC 630 expansion cards:

'''Compatible Video Cards:'''
* '''Apple Video System Card''' – Basic video capture
* '''Apple TV/Video System Card''' – TV tuner with remote control
* Third-party capture cards designed for LC 630

'''Video Input Specifications:'''
* Composite video input (NTSC/PAL)
* S-Video input on some cards
* Real-time video overlay capability
* QuickTime capture support

This feature allowed the LC 580 to function as both computer and television, particularly appealing for classroom multimedia applications.

=== Expansion Slots ===

==== LC PDS (Processor Direct Slot) ====
* 114-pin connector (LC III/520 enhanced standard)
* Backward compatible with 96-pin LC cards
* Direct 68040 bus access at 33 MHz
* Common cards: Apple IIe Card, Ethernet adapters, accelerators

==== Communication Slot ====
* Original Comm Slot standard (not Comm Slot II)
* Based on LC PDS architecture
* Modem installation disables external modem port
* Compatible cards: 14.4/28.8 kbps modems, 10BASE-T Ethernet

==== Video Input Slot ====
* LC 630-specific connector
* Provides direct video path to display circuitry
* Power and control signals for TV tuner cards
* Not present in LC 575 or earlier models

=== 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 || Supports 400K, 800K, 1.44 MB disks
|-
| '''NCR 53C96''' || SCSI controller || For CD-ROM and external devices only
|-
| '''IDE controller''' || Hard drive interface || Integrated into chipset, PIO Mode 3
|-
| '''CUDA''' || ADB/Power management || Handles ADB, power control, PRAM
|-
| '''AWACS''' || Audio controller || 16-bit stereo sound generation
|}

=== PowerPC Upgrade Path ===

Apple offered the '''Macintosh Processor Upgrade Card''' for the LC 580:
* 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 for older software

Additionally, the LC 580 logic board can be replaced with boards from:
* Power Macintosh 5200 LC
* Power Macintosh 6200 series
* Performa 5260, 5300, 6300 series
* Power Macintosh 5400, 6400, 5500, 6500 (requires power supply upgrade)

=== Overclock Modification ===

The LC 580 shares its logic board design with the LC 630, enabling a 40 MHz overclock:
* Same resistor modification as LC 630 (remove specific resistors)
* Increases CPU speed from 33 MHz to 40 MHz
* 21% performance improvement
* DOS Compatibility Card (if installed) remains unaffected
* Procedure documented in LC 630 overclocking guides