RetroTechCollection

Macintosh IIsi

The Macintosh IIsi is a desktop personal computer designed, manufactured, and sold by Apple Computer, Inc. from October 1990 to March 1993.[1] Introduced as a lower-cost alternative to the Macintosh IIci, the IIsi was Apple's entry-level professional Macintosh, with more expandability than the Macintosh LC which launched the same day.[2]

Macintosh IIsi
Macintosh IIsi
Specifications
ManufacturerApple Computer, Inc.
TypeDesktop Personal Computer
ReleasedOctober 15, 1990
DiscontinuedMarch 15, 1993
Intro priceUS$2,999 – $3,770
CPUMotorola 68030 @ 20 MHz
Memory1 MB RAM soldered (expandable to 17 MB)
Storage40 MB, 80 MB, or 160 MB SCSI hard drive
DisplayIntegrated video (640×480 @ 8-bit color)
Sound8-bit stereo output, 8-bit mono input
Dimensions4.0" H × 12.4" W × 14.9" D (10.2 × 31.5 × 37.8 cm)
Weight10 lbs (4.5 kg)
OS / FirmwareSystem 6.0.7 – Mac OS 7.6.1
PredecessorMacintosh IIci
SuccessorMacintosh Centris 610
CodenameErickson, Raffica, Ray Ban, Spin, Oceanic
Model no.M0360

The IIsi was the first Macintosh with built-in audio recording, featuring an integrated microphone input.[3] The compact desktop case was unique to the IIsi and not used for any other Macintosh model.

Architecture and Processor

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The Macintosh IIsi uses a Motorola MC68030 microprocessor running at 20 MHz.[4]

  • 32-bit internal registers with 32-bit data path
  • 24-bit or 32-bit addressing modes
  • 0.5 KB Level 1 cache (on-chip)
  • No Level 2 cache

The system bus runs at 20 MHz. Apple underclocked the IIsi from 25 MHz to 20 MHz to avoid cannibalizing sales of the more expensive IIci. Many users modified ("chipped") their IIsi to run at 25 MHz or 28 MHz.[5]

Floating Point Unit

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The Motorola 68882 FPU is optional and not included on the logic board. The FPU installs via the Apple NuBus Adapter card, which plugs into the Processor Direct Slot and converts it to a NuBus slot while providing the FPU socket.[6]

Memory

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RAM Configuration

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  • Soldered RAM: 1 MB on logic board
  • SIMM Slots: 4 × 30-pin SIMM slots
  • SIMM Speed: 100 ns minimum
  • Maximum RAM: 17 MB (Apple official), 65 MB (with unofficial 16 MB SIMMs)
  • SIMM Installation: Must be installed in matched groups of four identical SIMMs
  • Supported SIMM Sizes: 256 KB, 512 KB, 1 MB, 2 MB, 4 MB (8 MB and 16 MB SIMMs work but are not officially supported)

The IIsi's 1 MB of soldered RAM cannot be removed or disabled. When calculating total RAM, add this 1 MB to the SIMM capacity.[7]

ROM

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  • ROM Size: 512 KB
  • ROM Type: Usually soldered to the logic board
  • ROM SIMM Slot: Present on some units; may contain a ROM SIMM instead of soldered ROMs
  • ROM ID: $067C

Some IIsi units shipped with ROMs on a removable SIMM rather than soldered chips. The IIsi ROM is reportedly compatible with the Macintosh SE/30 and may provide 32-bit clean operation when installed.[8]

Video

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The Macintosh IIsi uses integrated video that shares main system RAM, reducing available RAM and impacting performance.[9]

Video Specifications

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  • Video Output: DB-15 connector
  • Video RAM: 64 KB – 320 KB (shared from system RAM, depending on resolution)
  • Maximum Resolution: 640 × 480 pixels
  • Color Depth: 8-bit (256 colors) at 640 × 480
  • Portrait Monitor Support: 640 × 870 at 4-bit (16 grays)

Video uses the slow 1 MB of soldered RAM first, making video performance slower than dedicated VRAM systems. Setting the disk cache to 768 KB or larger forces video operations to use the faster SIMM RAM instead.[10]

Audio

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The Macintosh IIsi was the first Macintosh with built-in audio input.[11]

  • Audio Output: 8-bit stereo, 22 kHz
  • Audio Input: 8-bit mono, omnidirectional microphone input
  • Output Jack: 3.5 mm stereo headphone jack
  • Input Jack: 3.5 mm microphone input
  • Internal Speaker: Mono speaker on daughterboard

The IIsi develops sound issues over time due to its modular construction. The internal speaker mounts on a daughterboard with spring contacts that connect to the logic board. Speaker vibrations cause fretting of the contact surfaces, resulting in intermittent audio dropouts. Cleaning the contacts with a pencil eraser fixes this.[12]

Storage

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Hard Drive

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  • Interface: SCSI (DB-25 external connector)
  • Standard Capacities: 40 MB, 80 MB, or 160 MB
  • Internal Bay: One 3.5" SCSI hard drive bay

Floppy Drive

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  • Drive Type: Apple SuperDrive (1.44 MB)
  • Floppy Capacity: 1.44 MB (HD) and 800 KB (DD)
  • Injection Type: Auto-inject
  • External Connector: DB-19 floppy port

Input/Output and Expansion

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Ports

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  • ADB Ports: 1 (Apple Desktop Bus for keyboard and mouse)
  • Serial Ports: 2 × Mini DIN-8 RS-422 (Printer and Modem)
  • SCSI Port: DB-25 connector
  • Floppy Port: DB-19 connector
  • Video Port: DB-15 connector
  • Audio Output: 3.5 mm stereo jack
  • Audio Input: 3.5 mm microphone jack

Expansion Slot

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The IIsi has a single Processor Direct Slot (PDS) compatible with Macintosh SE/30 expansion cards. The slot runs at 20 MHz instead of 16 MHz, so some SE/30 cards may not work.[13]

The Apple IIsi NuBus Adapter converts the PDS slot to accept standard 7-inch NuBus cards. This adapter also includes a socket for the optional 68882 FPU. With a slim hard drive, 12-inch NuBus cards may also fit.[14]

Power

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  • Power Supply: 160W internal
  • Input Voltage: 100V – 240V AC
  • Frequency: 50 – 60 Hz
  • Maximum Wattage: 160W
  • BTU per Hour: 547.2
  • PRAM Battery: 3.6V lithium half-AA
  • Soft Power: Yes (power controlled via ADB keyboard)
  • Pass-Through: Yes (power outlet on back for monitor)

Case Design

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The IIsi uses a unique compact desktop case not shared with any other Macintosh. The case uses clips and latches rather than screws, requiring no tools for disassembly.[15]

  • Dimensions: 4.0" H × 12.4" W × 14.9" D (10.2 × 31.5 × 37.8 cm)
  • Weight: 10 lbs (4.5 kg)

General Maintenance

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Common maintenance concerns include capacitor leakage, PRAM battery failure, and speaker contact corrosion.

For cleaning, battery maintenance, board inspection, and power supply procedures, see the Macintosh IIsi General Maintenance page.

PCB Schematics & Service Manual

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The Macintosh IIsi has a logic board, power supply, and speaker daughterboard. Apple Service Source documentation provides troubleshooting and repair information.

Apple Service Manual

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The complete Apple Service Source manual is at Macintosh IIsi Service Source. Additional manuals are in the Apple Service Source category.

Capacitor Replacement Guide

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The Macintosh IIsi logic board and power supply contain surface-mount electrolytic capacitors prone to leakage after 30+ years. Leaking capacitors corrode PCB traces and cause intermittent operation.

Logic Board Capacitors:

  • 2 × 220 µF 16V (axial electrolytic)
  • 11 × 47 µF 16V (surface-mount tantalum)

For capacitor specifications and procedures, see the Macintosh IIsi Capacitor Replacement Guide.[16]

Troubleshooting

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Common issues include startup failures, video problems, audio dropouts, and SCSI device issues. Many problems are caused by capacitor failure or PRAM battery leakage.

For diagnostics on power, video, Sad Mac errors, sound, and SCSI failures, see the Macintosh IIsi Troubleshooting page.

Technical Specifications

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System Overview

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Sub-system Specification (Macintosh IIsi, October 1990)
CPU Motorola 68030 @ 20 MHz
FPU Optional Motorola 68882 (via NuBus adapter)
Bus Width 32-bit data • 24-bit or 32-bit addressing
ROM 512 KB
RAM 1 MB soldered + 4 × 30-pin SIMM slots (17 MB max official)
L1 Cache 0.5 KB (on-chip)
L2 Cache None
Video Integrated, 640 × 480 @ 8-bit (shares system RAM)
Sound 8-bit stereo output • 8-bit mono input
Storage 40/80/160 MB SCSI HDD • 1.44 MB SuperDrive
Expansion 1 × SE/30 PDS (convertible to NuBus with adapter)
Ports ADB • 2 × Serial • SCSI • Floppy • Video • Audio I/O

Model Configurations

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Macintosh IIsi Model Numbers and Configurations
Order Number RAM Hard Drive Price (1990)
M0363LL/A 2 MB 40 MB US$2,999
M0364LL/A 5 MB 80 MB US$3,769
M0364LL/B 5 MB 80 MB —
M0491LL/B 3 MB 40 MB —
M0954LL/A 5 MB 160 MB —

Identification

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Identifier Value
Apple Model Number M0360
Gestalt ID 18
ROM ID $067C

See Also

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References

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  1. ↑ Macintosh IIsi: Technical Specifications, Apple Inc.—link(accessed 2026-02-09)
  2. ↑ Macintosh IIsi Specs, EveryMac.com—link(accessed 2026-02-09)
  3. ↑ Mac IIsi, Low End Mac—link(accessed 2026-02-09)
  4. ↑ Macintosh IIsi, Wikipedia—link(accessed 2026-02-09)
  5. ↑ Mac IIsi, Low End Mac—link(accessed 2026-02-09)
  6. ↑ Macintosh IIsi Specs, EveryMac.com—link(accessed 2026-02-09)
  7. ↑ Macintosh IIsi: Technical Specifications, Apple Inc.—link(accessed 2026-02-09)
  8. ↑ Mac IIsi, Low End Mac—link(accessed 2026-02-09)
  9. ↑ Macintosh IIsi, Wikipedia—link(accessed 2026-02-09)
  10. ↑ Macintosh IIsi, Wikipedia—link(accessed 2026-02-09)
  11. ↑ Mac IIsi, Low End Mac—link(accessed 2026-02-09)
  12. ↑ Macintosh IIsi, Wikipedia—link(accessed 2026-02-09)
  13. ↑ Mac IIsi, Low End Mac—link(accessed 2026-02-09)
  14. ↑ Macintosh IIsi Specs, EveryMac.com—link(accessed 2026-02-09)
  15. ↑ Macintosh IIsi, Wikipedia—link(accessed 2026-02-09)
  16. ↑ Caps! -- Macintosh IIsi, 68kMLA—link(accessed 2026-02-09)
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