The Model 30 was the
smallest of the original systems. The maximum central core storage size was 64K Bytes.
(Some OEM/PCM memory suppliers could enlarge this to 96K). It was common to have 16K or
even 8K Byte machines. The storage access time was 1.5 micro seconds and the machine had a
one Byte wide buss. The I/0 was controlled by internal Selector and Byte Multiplexer
channels. These two types of Channels Selector and Byte Multiplexer were used to access
the various I/0 devices. The selector for what was termed High Speed peripherals such as
Disk or Tape, and the Byte Multiplexer for the slower Printers, Card and Paper Tape
devices. A detailed description of the Standard Interface
can be found elsewhere in the Museum.
The operator consul was an IBM 1052 (a version of the IBM Golf Ball
typewriter). The channels shared the internal micro code with the CPU. This micro code was
stored by a paper Capacity Read Only Storage (CR0S) system. This looked like a pack of
punch cards and had a Blower Assembly to separate the cards.
