Apple personal computer of early 1990s

The IIsi shares some features with the SE/30 , some with the LC series, and some with the Mac II series. Like the SE/30, it has a 68030 PDS (Processor Direct Slot) for expansion. Like the LC , it has no built-in NuBus slot, is quite short, and has a curved front. But with an adapter, the PDS can be converted to a NuBus slot, making it a legitimate member of the Mac II family (all other members of the Mac II family have built-in NuBus slots).

The IIsi was designed as a less expensive, less expandable alternative to the Mac IIci . Cost saving measures included eliminating NuBus expansion slots, soldering 1 MB of RAM to the motherboard, and using a slower CPU (20 MHz instead of  25 MHz).

Although the IIsi was marketed as a 20 MHz computer, users quickly discovered it used parts rated at 25 MHz. (Apple had intended it as a 25 MHz computer, but chose to scale back the speed to avoid cutting into IIci sales.) Chipping the IIsi to 25 MHz – or even 28 MHz – is not unusual.

Specs (via Low End Mac)

• Cpu: 20 MHz 68030
• Fpu: 68882 (optional with NuBus adapter)
• Ram: 1 MB on motherboard, expandable to 65 MB using a 4-SIMM bank of 100ns 30-pin memory; can use 256 KB, 512 KB, 1 MB, 2 MB, and 4 MB SIMMs (you can use 8 MB and 16 MB SIMMs, although Apple does not officially support them)
• Rom: 512 KB, usually soldered to the motherboard, occasionally on a DIMM
• L2 Cache: none
• Hard Drive: 40 or 80 MB SCSI
• Floppy Drive: 1.4 MB double-sided
• Addressing: 24-bit or 32-bit
• Gestalt Id: 10
• Code Names: Erickson, Raffica, Raffika, Ray Ban, Spin, Oceanic
• Adb Ports: 2
• Pram Battery: 3.6V half-AA
• Weight: 10 lbs.
• Video Port: DA-15
• Serial Ports: 2 DIN-8 RS-422 ports on back of computer
• Scsi Ports: DB-25 connector on back of computer
• Sound: 8-bit stereo
• Audio In: 8-bit mono
• Power Supply: 160W
• The Ultimate Writing Machine: Quiet and free of interruptions , Andrew J Fishkin, Best Tools for the Job, 2007.09.20. For creative writing, turn off messaging, use a quiet computer, and reduce clutter on your screen. An old computer may be your best choice.
• See: Online resources and links for the Mac IIsi