On-Line Data-Acquisition Systems in Nuclear Physics, 1969: A MEDIUM-SIZED ON-LINE COMPUTER SYSTEM

On-Line Data-Acquisition Systems in Nuclear Physics, 1969, by H. W. Fulbright et al. National Research Council is part of the HackerNoon Books Series. You can jump to any chapter in this book here. Chapter 2: A MEDIUM-SIZED ON-LINE COMPUTER SYSTEM

1. Introduction

An EMR 6130 computer system has been installed and is being prepared for use with Columbia University's Neutron Velocity Spectrometer data-acquisition and analysis system. The spectrometer is characterized by high data rates and many events per burst. At present, peak arrival rates are approximately 106 events per second, with 40-60 events per burst and a burst rate of 70 Hz. The arrival distribution is random; therefore, 10 percent of the interarrival intervals are 100 nsec long, and 1 percent are 10 nsec long. In the future, peak arrival rates of 107 events/sec and 400-600 events per burst are possible, with a burst rate of 300 Hz. With an appropriate time-of-flight "front end," the 6130 will be able to handle the anticipated faster rates.

The EMR 6130 is a 16-bit, 775-nsec computer. The memory has a multibus structure which permits each bus to communicate simultaneously with a separate memory module. Up to four memory buses may be purchased. The Columbia system has two memory buses. If a high-speed buffered data channel is used, block transfer may occur at memory cycle speeds. With two buses, data may be stored in two memory modules at rates up to twice memory speed. Alternatively, one bus, channel, and one or more memory modules may be dedicated to data acquisition, while the central processor and standard peripheral devices, using the second bus, simultaneously operate in the remaining memory modules.

2. Description of the System

A block diagram of the Columbia system is given in Figure 5. The system has three 8k core modules. Memory bus 1 is dedicated to a high-speed channel serving the time-of-flight acquisition system. Memory bus 2 serves both the central processor and a second high-speed channel. Low-speed input-output devices, such as the operator's console, teletype, card reader, and plotter communicate directly through the processor. The high-speed input-output devices, namely, a magnetic tape unit, line printer, fixed head disk, and interactive CRT display, communicate through the channel.

The box designated as "time-of-flight system" represents special-purpose electronics, including a 50-mHz clock, time-quantizing circuits which "clock" an input event from one of the detectors to the nearest clock pulse following its arrival, a 50-mHz counter, and a 16-word derandomizing buffer capable of storing a new word of data (i.e., arrival time) every 20 nsec.

The number of channels, nominally 16,000, is limited not by the front end but by the amount of core available for histogram storage in the 6130 system. (For the high data rates anticipated in the future, the time-of-flight clock speed and derandomizing buffer data acceptance rate will be increased to 100 mHz. At the same time, an accumulating buffer of several hundred words capacity, with a 20-mHz data acceptance rate, will be added to empty the derandomizing buffer and store temporarily the time-of-arrival data prior to its transmission to the 6130 system.)

FIGURE 6 Diagram illustrating mode of utilization of core memory in the Columbia System shown in Figure 5.

3. How the System is Used

During the time-of-flight experiment, memory is utilized as follows (see Figure 6). The channel dedicated to data acquisition writes on alternate bursts, into two buffer regions, of approximately 100 words each, in the top of memory module 3. The remaining parts of memory module 3 and all module 2 will be devoted to histogram storage (i.e., time-of-flight channels). Module 1 will contain a stripped-down monitor program and all data-handling programs, including buffer regions for the external devices other than the time-of-flight front end. Programs will be capable of referring to all module 1 or 2 in full concurrency with data acquisition. Reference to module 3 will also overlap data acquisition, except for a period of high input data rate of 100-to 200-µsec duration per burst. With the type of memory allocation described, the system will permit the use of all standard I/O devices, concurrent with the essential operations of input data buffering and histogram generation.

Thus, new data may be stored on, or old data retrieved from, the disk or magnetic tape; either new or old data may be displayed on the CRT; and the same or other data may be output with the plotter or line printer. Control information will be input from the teletype, the operator's console, or from special-purpose switches. The importance to the physicist is that hard copy output is immediately available during data acquisition and may be used to monitor, or modify, the experiment.

Subsequent to the input data increase, a high-speed memory incrementing channel will be used to input time-of-flight data directly to the histogram area. With this channel the buffer area in module 3 will no longer be required. Histogram data will be stored in all modules 2 and 3, and no program intervention will be required for histogram generation.

Between data-acquisition runs, the system will be used for data analysis.

4. Present Status

The computer, with two memory modules and one channel and bus, was delivered in July 1968. The remaining memory module channel and bus were delivered in the fall of 1968, the CRT arrived in June 1969, and the line printer (which was not purchased from EMR) came shortly afterward. The first time-of-flight run with this system was scheduled for December 1969. During the period from delivery to the first run, one full-time programmer and approximately half the time of one physicist were devoted to the debugging of manufacturer-supplied programs and the writing of the on-line programs required for the run.

It has been hoped that the system would be used extensively for the analysis of previously acquired data, beginning shortly after delivery; however, very little such use has proved possible, essentially because of the unreliability of the 100-cpm card reader supplied by EMR. The lack of a line printer was also a factor. A more reliable reader has been purchased. The delivery of a line printer should rectify the second need.

The development of high-speed, buffered, time-of-flight front ends has been a continuing interest at Columbia. It is therefore difficult to estimate the precise costs of the time-of-flight system developed for use with the 6130. A rough estimate of the design and development time is approximately 3 engineer man years.

5. Lessons from Development and Testing Experience

Columbia chose to order the EMR 6130, even though at that time (1966) it was not in production, because it seemed a very powerful machine which matched the needs of the system planners. The alternate possibility open was to order a larger, much more expensive machine of proven capability. As it turned out, difficulties in the development of the 6130 caused a delay of over a year in the delivery of the main frame and of over two years in the delivery of the CRT display. (When these delays became apparent, EMR loaned Columbia a 24-bit computer and also a small display for use during the interim period.) The EMR 6130 is perhaps the most powerful 16-bit computer available today, in spite of one or two changes in the original specifications, but in order to get it Columbia apparently traded time for money.

6. Cost

The costs of the Columbia University EMR 6130 system are given in Table 3.

Purchased from printer manufacturer with 6130 interface.

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H. W., Fulbright et al. 2013. On-Line Data-Acquisition Systems in Nuclear Physics, 1969. Urbana, Illinois: Project Gutenberg. Retrieved May 2022 from https://www.gutenberg.org/files/42613/42613-h/42613-h.htm#Page_28

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