Console Typewriter - GE 235 System Manual

Console Typewriter
accepts instructions from the operator.
a prints instructions to the operator.
a
monitors system operations.
a prints direct output from the central processor.
MAGNETIC CORE MEMORY
The memory portion of the Central P r o c e s s o r i s the immediate-access storage element for the
GE-235 system. Both the data to be processed and the controlling instructions a r e held in
memory and a r e called for by the control unit a s required.
The memory i s composed of magnetic c o r e s .050 inch in diameter; each core i s capable of
storing one unit of information, r e f e r r e d to a s a bit. The basic unit of memory storage i s the
"word"
--
each word consisting of 20 bits plus a parity check bit. Each word has i t s own unique
address.
The size of the basic memory i s 4096 words. The memory design allows for an expansion to an
8192-word memory o r to a 16,384-word memory without the necessity of expensive retrofits.
The 16,384-word memory i s divided into two groups of 8192 words each, referred to a s the upper
bank and the lower bank.
Minimum instruction word access and execution time i s 6 microseconds. A data word transfer
to o r from memory, including the instruction word time, i s accomplished in 12 microseconds;
a double word transfer i s made in 18 microseconds. The transfer of words to and f r o m memory
a r e made in one-word parallel form; that is, the word bits a r e transferred simultaneously.
Internal checking i s accomplished by generating and storing a parity bit when a word i s trans-
f e r r e d to memory, and by recomputing and verifying that parity bit when the word i s read f r o m
memory.
The effect of a p u i t y e r r o r may be controlled to meet the needs of the application by
console STOP/RUN switch operation.
W O R D F O R M A T S
The GE-235 can process data in either binary o r alphanumeric form. This feature permits both
modes of operation to take advantage of the particular characteristics of a given application.
Alphanumeric (BCD) Words
When c a r d s punched in Hollerith code a r e used a s computer input, the information contained in
each of the 80 columns i s automatically converted into a six-bit binary-coded-decimal (BCD)
character. Thus, 3 alphanumeric characters occupy 18 of the 20 bit positions of an alphanumeric