- Macintosh IIsi
Mac_specs|
October 15 1990 |MSRP=2999|CPU=Motorola 68030
CPUspeed=20 MHz|OS=System 6.0.7 to 7.6.1|RAM=1MiB , expandable to 65 MiB|RAMtype=100 ns 30-pinSIMM s
Discontinued=March 15 ,1993 The Macintosh IIsi was a compact three-box desktop unit, effectively a cut-down
Macintosh IIci in a smaller case (used for no other Macintosh model), made cheaper by the redesign of the motherboard and the deletion of all but one of the expansion card slots (a singleProcessor Direct Slot ). It was introduced as a low-cost alternative to the professional desktop models for home use, but offered more features and performance than the LC series. It had color and could drive a number of different external monitors, with a maximum screen resolution of 640×480 in eight-bit color.It shipped with either a 40-MB or 80-MB internal hard disk, and a 1.44-MB floppy disk drive. The MC 68882 FPU was an optional extra, 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. The IIsi was the first Macintosh released with built-in sound-in capabilities. TheMacintosh LC , which was announced at the same time and also had a sound-in port, was released a number of months after the IIsi.A bridge card was available for the IIsi to convert the Processor Direct slot to a standard internal
NuBus card slot, compatible with the other II-series Macintoshes. The bridge card included a math co-processor to improve floating-point performance.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 MiB 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 faster RAM installed in theSIMM 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 main logic board, with springy contacts. Speaker vibrations led to
fretting of the touching surfaces. The problem could be solved by removing the logic board and using a pencil eraser to clean the contacts of the daughterboard holding the loudspeaker.Because of its heritage as a cut-down IIci, a simple modification carried out by many owners was to substitute a new
clock crystal to increase the speed to 25 MHz.External links
* [http://docs.info.apple.com/article.html?artnum=112177 Macintosh IIsi technical specification] at apple.com
IIsi
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