Macintosh LC III Developer Note

The Macintosh LC III Developer Note is Apple's hardware and software reference for the Macintosh LC III, published by Apple's Developer Technical Publications in 1993. The hosted copy is Apple's distilled PDF of 58 pages (dated March 1995): front matter, a 40-page hardware chapter, a short software chapter and three foldout drawings of the expansion card (Apple drawing 062-0487-B).

Contents

Page numbers are the document's own.

• Preface: about this note, supplementary documents, conventions and abbreviations, p. vii
• Chapter 1, Hardware, p. 1: introduction and features, p. 2; design differences from the LC II and block diagram, pp. 3-4; compatibility issues (RAM SIMM socket, processor-direct slot, video modes, floppy disk controller, FPU), p. 5; hardware overview: 68030, Omega clock chip, Sonora integrated controller (timing, address decode and memory map, video, sound, GLU and VIA, floppy), ROM, RAM and the RAM expansion interface (Table 1-2 SIMM configurations, Table 1-3 SIMM pinout, Figure 1-2 SIMM design guide), pp. 6-13; video interface (VRAM, supported monitors and Table 1-4 video modes, sense codes, internal video connector, timing), pp. 14-24; sound, serial and SCSI interfaces, floppy interface, p. 25-27; ADB microcontroller (ADB, real-time clock and PRAM, power-on reset, keyboard reset and NMI), pp. 28-29; the processor-direct slot (pinout, signals, load and drive limits, Table 1-16 power budget on p. 37, design guidelines, connectors), pp. 29-40
• Chapter 2, Software, p. 41: the LC III ROM, identifying the LC III, system software, p. 42
• Foldouts 1-3: expansion card design guide, component height restrictions and assembly guide

What it settles

• The processor is a 68030 at 25 MHz, with 32-bit transfers to RAM and ROM and 16-bit transfers to VRAM (p. 6).
• ROM is 1 MB on the logic board, in two 40-pin 256K × 16 chips (pp. 2, 8). Apple's LC series Service Source prints "512K expandable to 1 MB" for the same machine.
• RAM is 4 MB soldered (eight 1M × 4 chips) plus one 72-pin SIMM of 1 to 32 MB, 80 ns fast page mode, built to Apple's own specification with tin contacts; 36 MB in total, of which 8 MB can be used in 24-bit mode (pp. 2, 7, 9).
• Video: 512 KB of VRAM on the board and a 68-pin socket for a 256 KB, 80 ns VRAM SIMM (768 KB); the colour depth each monitor gets with each amount is in Table 1-4 (pp. 14-15).
• The FPU socket is a PLCC socket for a 68882, and some configurations may have shipped with an FPU (pp. 2-3).
• The 114-pin processor-direct slot takes 96-pin LC and LC II cards. The power budget is 800 mA at +5 V, 20 mA at −5 V and 165 mA at +12 V, 4 W in total, and Apple recommends that cards ground /FANSPEED (p. 37).
• The ADB port supplies up to 200 mA through a 1 A fuse; Command-Power gives an NMI and Command-Control-Power a hard reset (pp. 28-29).
• The Gestalt machine type is 27, and the machine shipped with System 7.1 and an enabler on the Install Me First disk (p. 42).

What it does not contain

The note has no service procedures, parts list, schematics or component values, and gives no power supply ratings or battery details beyond saying that a backup battery keeps the clock and PRAM running. For service, use the Macintosh LC Series/ Quadra 605 Service Source.

Pages that cite this document

• Macintosh LC III: chips, ROM, RAM, video modes, FPU socket, slot power budget, keyboard reset
• Macintosh LC III General Maintenance: specifications and slot power budget
• Macintosh LC III Capacitor Replacement Guide: FPU socket
• Macintosh LC III+ and Macintosh LC III+ General Maintenance: the 25 MHz board the 33 MHz LC III+ is derived from, FPU socket, slot power budget
• Macintosh LC II Troubleshooting: keyboard reset and NMI on the LC and LC II

Download: Macintosh LC III Developer Note.pdf