CDC 1604

Architecture

left|400px|2-views drawing of a CDC 1604 with scaling

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Memory in the CDC 1604 consists of 32K 48-bit words of magnetic core memory with a cycle time of 6.4 microseconds. It is organized as two banks of 16K words each, with odd addresses in one bank and even addresses in the other. The two banks are phased 3.2 microseconds apart, so average effective memory access time was 4.8 microseconds. The computer executes about 100,000 operations per second.

Each 48-bit word contains two 24-bit instructions. The instruction format is 6-3-15: six bits for the operation code, three bits for a "designator" (index register for memory access instructions, condition for jump (branch) instructions) and fifteen bits for a memory address (or shift count, for shift instructions).

The CPU contains a 48-bit accumulator (A), a 48-bit Auxiliary Arithmetic register (Q), a 15-bit program counter (P), and six 15-bit index registers (1-6).{{cite book |title=Computer Programming and Computer Systems

Internal integer representation uses ones' complement arithmetic. Internal floating point format is 1-11-36: one bit of sign, eleven bits of offset (biased) binary exponent, and thirty-six bits of binary significand.

The most-significant three bits of the accumulator are converted from digital to analog and connected to a tube audio amplifier contained in the console. This facility could be used to program audio alerts for the computer operator, or to generate music. Those familiar with the inner workings of the software could often hear what parts of a task were being performed by the CDC 1604; as a debugging aid, for example, a never-ending repetitive musical phrase indicated the program was stuck in a loop.

Uses and applications

In 1960, one of the first text-mining applications, Masquerade, was written for the Marathon Oil Company in Findlay, Ohio. Masquerade was a text-mining program that used syntactic structures underlying text data to mask out words and phrases for searching purposes.{{cite journal |title=MASQUERADE: Searching the full text of abstracts using automatic indexing During 1969, Fleet Operations Control Center, Pacific (FOCCPAC at Kunia) on Oahu in Hawaii launched an Automated Control Environment (ACE) using a cluster of five CDC 160As to supervise a multi-tasking network of four CDC 1604s.

The Minuteman I was the first U.S. solid-rocket ICBM system to be fielded. There were two entirely separate ground station designs which were developed independently. The smaller, more elegant, single silo design incorporated two redundant CDC 1604 computer systems, each equipped with dual cabinets containing four 200 bpi magnetic tape drives. The computers were used to pre-compute guidance and aiming control information. Results based on current weather and targeting information were downloaded into the missile prior to launch. Model displays of both of these ICBM ground station designs, including block models of the CDC 1604 computers, may be viewed at the Octave Chanute Aerospace Museum in Rantoul, Illinois.

The third version of the PLATO computer-based educational system was implemented on a CDC 1604-C.

JOVIAL was used as the programming language of the CDC 1604, while was used to program shared services supported by the CDC 160A. Naval Command and Systems Support Activity (NAVCOSSACT) based at the Washington Navy Yard provided systems and training support.

The CDC 1604 was used to compose Sailboat and other artworks by Sam Schmitt and Stockton Gaines.

Similar machines

The 1604 design was used by the Soviet nuclear weapons laboratory. Their BESM-6 computer, which entered production in 1968, was designed to be somewhat software compatible with the CDC 1604,{{cite book

The 924

Length : 157 cm Width : 66 cm The CDC 924 is a 24-bit computer that supported the use of "any input-output devices capable of communicating with the 160 and/or 1604 computer,"{{cite web

Like many CDC processors, it used ones' complement arithmetic.

Some advanced features of the 924, which included 64 instructions, were:

• Six index registers. The value "7" was reserved to indicate indirect-addressing.
• an execute instruction (in what the hardware reference manual called "a subroutine of a single instruction").
• powerful Storage Search instructions.

Explanatory notes

References

Photos

• CDC 1604
• 1604 in Cray Computer Museum
• same museum's 1604, different view

References

1. [http://ed-thelen.org/comp-hist/BRL64-c.html#CONTROL-DATA-1604A 1964 Computer Survey, PDF]
2. [http://bitsavers.trailing-edge.com/pdf/cdc/1604/031a_1604_Computer_Vol_1_Description_and_Operation_Dec60.pdf CDC 1604 Computer, Vol 1, Description and Operation (Dec 60, pdf)]
3. "The BUNCH".
4. Ed Thelen. "CDC 160A".
5. (1963). "Control Data 1604-A Computer Reference Manual". [[Control Data Corporation]].
6. Fleming, George. "CDC 1604".
7. "PLATO - computer-based education system".
8. "CDC 160A Languages enabled".
9. "Sam Schmitt {{!}} Database of Digital Art".
10. "Control Data Corporation Collection - Historical Timeline".
11. [http://bitsavers.trailing-edge.com/pdf/cdc/924/168B_CDC_924_Reference_Manual_Oct62.pdf CDC 924 Reference Manual (PDF, Oct 62)]