Apple Macintosh IIsi
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 single Processor 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. The Macintosh LC, which was announced at the same time and also had a sound-in port, was released a number of months after the IIsi.
•introduced 1990.10.15 at $3,800; discontinued 1993.03.15
•requires System 6.0.6 to 7.6.1
•CPU: 20 MHz 68030
•ROM: 512 KB, usually soldered to the motherboard, occasionally on a DIMM
•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)
•built-in 8-bit video, supports 512 x 384 and 640 x 480 at 8-bits or portrait monitor (640 x 870) at 4-bits (uses 64-320 KB of RAM for video, not separate VRAM)
•video port: DB-15
•ADB: 2 ports for keyboard and mouse
•serial: 2 DIN-8 RS-422 ports on back of computer
•SCSI: DB-25 connector on back of computer
•hard drive: 40 or 80 MB
•sound: 8-bit stereo
•audio in: 8-bit mono
•SE/30 PDS slot (runs at 20 MHz, so not all SE/30 cards will work - can be converted to NuBus slot with adapter)
•NuBus slot with adapter in PDS, supports 7" cards, 12" cards may fit with a slim hard drive
•size (HxWxD): 4.0" x 12.4" x 14.9"
•weight: 10 lbs.
•PRAM battery: 3.6V half-AA
•power supply: 160W
•Gestalt ID: 10
•part no.: M0360
•addressing: 24-bit or 32-bit
This is complete with a Macintosh Portrait display monitor and a Frog systems 100e
Our model No: PA1033E has a serial number of 11212717W was kindly donated by Mrs Hilary Yates and was the computer last used by John Yates who wrote the article Notes by a physicist who dabbled with computers. This can be seen at
We also have John's Personal LaserWriter
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This exhibit has a reference ID of CH5454. Please quote this reference ID in any communication with the Centre for Computing History.