The Macintosh IIsi is a

personal computer A personal computer, commonly referred to as PC or computer, is a computer designed for individual use. It is typically used for tasks such as Word processor, word processing, web browser, internet browsing, email, multimedia playback, and PC ...

designed, manufactured and sold by Apple Computer, Inc. from October 1990 to March 1993. Introduced as a lower-cost alternative to the other Macintosh II family of desktop models, it was popular for home use, as it offered more expandability and performance than the Macintosh LC, which was introduced at the same time. Like the LC, it has built-in sound support, as well as support for color displays, with a maximum screen resolution of 640 × 480 in 8-bit color. The IIsi remained on the market for two and a half years and was discontinued shortly after the introduction of its replacement, the Centris 610.

Hardware

The IIsi's case design is a compact desktop unit not used for any other Macintosh model, one of the few Macintosh designs that was used for a single model. Positioned below the Macintosh IIci as Apple's entry-level professional model, the IIsi's price was lowered by the redesign of the motherboard substituting a different memory controller and the deletion of all but one of the expansion card slots (a single Processor Direct Slot) and removal of the level 2 cache slot. It shipped with either a 40 MB or 80 MB internal hard disk, and a 1.44 MB floppy disk drive. The Motorola 68882 FPU was an optional upgrade, mounted on a special plug-in card. Ports included SCSI, two serial ports, an ADB port, a floppy drive port, and 3.5mm stereo headphone sound output and microphone sound input sockets. A bridge card was available for the IIsi to convert the Processor Direct slot to a standard internal NuBus card slot, compatible with other machines in the Macintosh II family. The bridge card included the 68882 FPU to improve floating-point performance. The NuBus card was mounted horizontally above the motherboard. To cut costs, the IIsi's video shared the main system memory, which also had the effect of slowing down video considerably, especially as the IIsi had 1 MB of slow RAM soldered to the motherboard. David Pogue's book ''Macworld Macintosh Secrets'' observed that one could speed up video considerably if one set the disk cache size large enough to force the computer to draw video RAM from the faster RAM installed in the SIMM banks. The IIsi also suffers from sound difficulties: over time, the speaker contacts can fail, causing the sound to periodically drop out. This problem was caused by the very modular construction of the computer, where the mono loudspeaker is on a daughterboard under the motherboard, with springy contacts. Speaker vibrations led to fretting of the touching surfaces. The problem could be solved by removing the motherboard and using a pencil eraser to clean the contacts of the daughterboard holding the loudspeaker. As the IIsi is the only Macintosh to use this case design, these issues were never corrected in a subsequent model. The IIsi was designed to be easily and cheaply manufactured, such that no tools were required to put one together – everything is held in place with clips or latches. Because of its heritage as a cut-down IIci, it was a simple modification to substitute a new

clock A clock or chronometer is a device that measures and displays time. The clock is one of the oldest Invention, human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month, a ...

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

to increase the system's

clock rate Clock rate or clock speed in computing typically refers to the frequency at which the clock generator of a processor can generate pulses used to synchronize the operations of its components. It is used as an indicator of the processor's s ...

to 25 MHz for a slight increase in performance and a large increase in video rendering speed.

Known users

Charles Bukowski Henry Charles Bukowski ( ; born Heinrich Karl Bukowski, ; August 16, 1920 – March 9, 1994) was a German Americans, German-American poet, novelist, and short story writer. His writing was influenced by the social, cultural, and economic ambien ...

was an enthusiastic user of the IIsi.

Timeline

References

External links

Macintosh IIsi teardown
at ifixit.com {{Apple hardware before 1998 si IIsi IIsi IIsi IIsi Computer-related introductions in 1990 Products and services discontinued in 1993