The system used electrostatic storage, consisting of 72 Williams tubes with a capacity of 1024 bits each, giving a total memory of 2048 words of 36 bits each. Each of the 72 Williams tubes was three inches in diameter. Memory could be expanded to a maximum of 4096 words of 36 bits by the addition of a second set of 72 Williams tubes or by replacing the entire memory with magnetic core memory. The Williams tube memory and later core memory each had a memory cycle time of 12 microseconds. The Williams tube memory required periodic refreshing, mandating the insertion of refresh cycles into the 701s timing. An addition required five 12 microsecond cycles, two of which were refresh cycles, a multiplication or division required 38 cycles (456 microseconds).
Numbers were either 36 bits or 18 bits long, signed magnitude, fixed point.
The IBM 701 had only 2 programmer accessible registers:
The IBM 701 system was composed of the following units:
Nineteen IBM 701 systems were installed. The University of California at Livermore developed a language compilation and runtime system called the KOMPILER for their 701. A Fortran compiler was not released by IBM until the IBM 704.
The 701 can claim to be the first computer displaying the potential of artificial intelligence in the Samuel Checkers-playing Program.
The successor of the 701 was the index register-equipped IBM 704, introduced 4 years after the 701. The 704 was not compatible with the 701, however, as the 704 increased the size of instructions from 18 bits to 36 bits to support the extra features.