On-Line Data-Acquisition Systems in Nuclear Physics, 1969: Chapter 3- BREAKDOWN OF DATA FOR ANALYSIS

Because of the nature of the data the reviewer separated each system into three parts for the purpose of analysis: (1) the data-acquisition central processor (CPU); (2) the standard computer input-output (I/O) devices such as magnetic tapes, disks, card readers, printers; (3) the complete data-acquisition subsystem (DAS). (See Figure 12.) This breakdown has the advantage that the costs of the first two parts of the system are usually fairly accurately known. The cost of the DAS includes the price of all manufactured units closely involved in its assembly, including scalers, ADC's, pulse-height analyzers, and the like (but not detection equipment), together with the expenses associated with all special construction, including engineering, fabrication, and parts. All engineering and fabrication costs associated with the entire system can logically be charged against the DAS, because the CPU and I/O parts, being assembled from standard manufactured items, generally are installed by the manufacturer without much effort or expense on the part of the laboratory personnel. Questions occasionally arose in connection with the assignment of the cost of interfacing the DAS to the CPU. Such costs were assigned to the DAS when the units involved were of a custom-built nature and to the CPU when they were manufacturer's items incorporated in the computer frame. The very wide range of types of data-acquisition equipment in use necessarily contributes to the spread in DAS costs. Although a number of items of uncertain costs are lumped together in this definition of the DAS, the procedure adopted is believed to have led to a valuable overall picture of the pattern of expenditures.

A fourth item of importance in the analysis is the cost of system software programming. This is almost entirely a manpower item, assuming that program testing and debugging can be carried out without charge for the computer time involved. Here there is considerable uncertainty in the estimates, especially with respect to university installations as well as systems which have been in operation for a long time, e.g., the large system at Argonne.

The total cost of a system is taken to be the sum of the four items listed above, namely, the CPU, the standard I/O system, the DAS, and the system software expenditures. In all likelihood the total costs tend to be too small rather than too large because of incomplete assignments of charges of various sorts, especially manpower. In many cases the totals seem reliable to 10 or 20 percent, while in a few others an error of 30 or even 40 percent would not be surprising.