CENTRAL PROCESSING UNITS

This chapter discusses the designs of computer systems, such as IBM 1620, CDC 1604, IBM 1401, KDF 9, and CDC 6600. The CDC 1604 has a core memory of 32,768 words. It has an accumulator and an MQ register, index registers, and a control register. Numbers can be represented as binary integers or as binary floating-point numbers. The IBM 1620 is a decimal machine with a memory organized into characters. The memory is made of magnetic cores and each core represents one bit but the machine regards a group of six cores as one unit and uses the group of six to represent one decimal digit. The IBM 1401 has a magnetic core memory that contains 1400, 2000, 4000, 8000, or 16,000 characters. Each character consists of 8 bits. The two extra bits, compared with the 6-bit characters of the 1620, enable the 1401 to store either decimal or alphabetic information in one character. The KDF 9 computer has a magnetic core memory of 32,768 words. Each word holds 48 bits. Each word can be regarded as a 48 bit integer or as a floating-point number or as eight 6 bit characters or as six 8 bit syllables. The CDC 6600 was first delivered in 1964. It consists of one central processor, 10 peripheral processors, and the usual peripheral equipment. The CDC 6600 has an operating system that controls the use of the peripheral processors and the input–output equipment.