Generalizing the Athena computer



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Although it is highly reliable and easily adaptable, the Athena computer lacks features which are essential for general computational purposes. There is no indexing capability. When the machine is program controlled, random accessible memory is limited to the 256 words of core memory although an 8192 word magnetic drum is available. Sequential programing is difficult when using extended sequence operations (multiply, divide, and shift) since the machine continues to read sequential addresses but ignores their contents until the extended sequence operation is complete. The length of the extended sequence operation is variable and must be compensated for in programing. A generalization of the Athena was achieved by eliminating or correcting these problems. A criterion of retaining the computer’s inherent reliability and flexibility was applied throughout the conversion process. An indexing feature was added that allows complete indexing of core memory and most of drum memory. New operation- codes were created to facilitate the full use of indexing and a versatile application of the index register. The magnetic drum was converted to a full-time random access memory. Data is read from the drum and placed in the accumulator or the contents of the accumulator can be written on the drum For flexibility, the programer can Read/Write in drum word length (18 bits) or in accumulator half word length (12 bits) Either the upper or lower accumulator half word may be stipulated. The programing problem associated with extended sequence operations was eliminated.