Macintosh LC III

The Macintosh LC III is a personal computer released by Apple on February 10, 1993. The LC III addressed the main performance limitation of earlier LC models by implementing a full 32-bit data bus, providing a substantial performance improvement over the Macintosh LC II.

Macintosh LC III

Macintosh LC III
Specifications
Manufacturer	Apple Computer, Inc.
Type	Personal Computer
Released	February 10, 1993
Discontinued	February 14, 1994
Intro price	US$1,349
CPU	Motorola 68030 @ 25 MHz
Memory	4 MB RAM (expandable to 36 MB)
Storage	80 MB SCSI HDD, 1.44 MB SuperDrive
Display	640×480 8-bit (512K VRAM) or 16-bit (768K VRAM)
Sound	8-bit stereo input/output
Dimensions	2.9" H × 12.2" W × 15.3" D
Weight	8.8 lbs (4.0 kg)
OS / Firmware	System 7.1 – System 7.6.1
Predecessor	Macintosh LC II
Successor	Macintosh LC III+
Codename	Vail, Elsie III
Model no.	M1254

Model Variants

The LC III was sold as the Performa 450 in consumer markets with bundled software.

Architecture and Processor

The LC III uses a Motorola 68030 processor running at 25 MHz with a full 32-bit data bus—a significant improvement over the 16-bit bus of the LC and LC II. This change substantially improved memory performance and overall system responsiveness.

The LC III includes a socket for an optional Motorola 68882 FPU (Floating Point Unit), the first LC to offer FPU support.

The Gestalt ID for the Macintosh LC III is 27.

Memory and Storage

RAM Configuration

The LC III shipped with 4 MB of RAM standard, expandable to 36 MB. A significant change from earlier LCs: the LC III uses a single 72-pin SIMM slot instead of 30-pin SIMM pairs.

RAM Configurations

Configuration	SIMM Required
4 MB	4 MB 72-pin SIMM (or 4 MB onboard)
8 MB	4 MB onboard + 4 MB SIMM
12 MB	4 MB onboard + 8 MB SIMM
20 MB	4 MB onboard + 16 MB SIMM
36 MB	4 MB onboard + 32 MB SIMM

Video RAM

The LC III includes 512 KB of VRAM onboard, expandable to 768 KB with a 256 KB VRAM SIMM:

• 512 KB VRAM: 640×480 at 8-bit (256 colors)
• 768 KB VRAM: 640×480 at 16-bit (thousands of colors)

ROM

The LC III contains 1 MB of ROM, double that of earlier LC models.

Storage Systems

Standard storage included:

• 80 MB internal SCSI hard drive
• 1.44 MB SuperDrive

Input/Output and Expansion

Port Configuration

• 1× Apple Desktop Bus (ADB) port
• 1× External SCSI (DB-25)
• 1× Audio input (3.5mm stereo minijack)
• 1× Audio output (3.5mm stereo minijack)
• 2× Serial ports (Mini DIN-8)
• 1× Video output (DA-15)

Expansion

The LC III features a single LC Processor Direct Slot (LC PDS) and an FPU socket (PGA) for the 68882 coprocessor.

General Maintenance

For detailed maintenance practices including cleaning, PRAM battery management, and connector care, refer to the dedicated Macintosh LC III General Maintenance page.

Troubleshooting

A comprehensive troubleshooting guide addressing common issues with the Macintosh LC III is available on the Macintosh LC III Troubleshooting page.

Capacitor Replacement

The Macintosh LC III logic board contains surface-mount electrolytic capacitors that commonly fail due to age. Detailed replacement guidelines can be found on the Macintosh LC III Capacitor Replacement Guide page.

Important: The LC III has a known factory defect where capacitor C22 was installed with reversed polarity due to a silkscreen error. See the capacitor replacement guide for details.

Technical Details

Macintosh LC III Technical Specifications

Component	Specification
CPU	Motorola 68030 @ 25 MHz
FPU	Optional 68882 (socket provided)
PMMU	Integrated in 68030
Data Bus	32-bit
System Bus	25 MHz
ROM	1 MB
RAM	4 MB (max 36 MB)
VRAM	512 KB (max 768 KB)